What Industry Owes to Chemical Science

THE IZSG1SEER" SERIES.

W H A T I N D U S T R Y O W E S

T O C H E M I C A L S C I E N C E .

RICHARD B. PiLCHER,

FRANK BL'TLER-JOXES. B..h. tC*r.taD.j, A.l.C

8.r GEORGE BEIL3Y, LL.D.. F.R.S..

London:CONSTABLE & COMPANY, LTD.,

10, Orange Street, Leicester Square, W.C.

19IS.

PRINTED IN* GREAT BRITAIN.

INTRODUCTION vii

PREFACE xiii

Chap. I. MINERALS AND METALS 1II. HEAVY CHEMICALS AND ALKALI 22

III. COAL ASD COAL GAS 34

IV. DYES, EXPLOSIVES, AND CELLULOSE ... 41

V. OILS, FATS, AND WAXES 53

VI. LEATHER 59

VII. RUBBER (53

VIII. MORTAR AND CEMENT tf5IX. REFRACTORY MATERIALS 08

X. GLASS AND ENAMELS 70

XI. POTTERY AND PORCELAIN 77

XII. CHEMICAL PRODUCTS 80

XIII. PHOTOGRAPHY 90XIV. AGRICULTURE AND FOOD 95

XV. BREWING 104

XVI. ALCOHOL, WINES AND SPIRITS 109

XVII. TOBACCO, INKS, PENCILS, ETC 115

XVIII. GASES 122XIX. GOVERNMENT CHEMISTRY 133

CONCLUSION 3 38

BIBLIOGRAPHY 141

INDEX 14-1

INTRODUCTION.

AMIDST the ifood nf opinions and advice on therelations of .science* t<> education and industrialprosperity with ivhii.-h we have been delugedduring the past two or three years, we may turnwith welcome relief to the unernbellished recordsof work done and of ends accomplished which theauthors Live h-re presented for our enlightenmentand encouragement. The majority among usstood much in need of enlightenment on thissubject, and many of us wilL feel grateful for theencouragement which is to be derived from the.serecords of past achievement. The«- records .supplyit complete answer to a question with which mostchemists have had to deal at one time or anotherduring their career : what is the place of thechemist in practical life, and what part has hetaken in industrial and social development ?

The engineer ministers to the. comfort and.convenience of the community in ways whichcan hardly escape the notice even of the man inthe street. The Forth Bridge, the ocean grey-hound, the motor car and the aeroplane are a tonce recognised ay the fruits of his skill and energy,

WHAT INDUSTRY OWES

but for the most part, the work of the chemist isinobvious, and is little, if at all, understood. Butthe chemist and his half-brother, the metallurgist,have all the time been hard at work in the back-ground, helping to provide the engineer withmetals and other materials of new and improvedqualities, without which he could not have producedthe machines and structures which represent thetriumphs of his art.

In many other directions chemistry has beenthe handmaid of arts and crafts, which maketheir appeal to the public on far other groundsthan those of the chemical and other scientifichelp they have laid under contribution.

But chemistry also has its own triumphs, andthose who will take the trouble to study this workwill be rewarded with visions of achievement inthis field which they had not hitherto dreamt of.

These records ought to prove stimulating andsuggestive to those whose sons and daughtershave not yet selected a calling or profession. Theplace of chemistry in the national life has beenfar more important than the majority of educatedpeople have imagined, and this place bids fair tobecome of vastly increased importance in the nearfuture. The special message for parents andteachers is, therefore, that trained chemists will,in the near future, be in increased demand forindustrial and official positions.

TO CHEMICAL SCIENCE ix

For the responsible teachers of chemistry thereare other messages also, if they care to seek forthem ; for from these records of achievementmuch may be learned as to the actual needs ofindustry on its scientific side, and as to the typesof workers who will have to be trained if theseneeds are to be properly met.

The great body of teachers of science on the onehand, and the still greater body of manufacturerson the other hand, have been equally at sea as tohow (a) the results of scientific discovery, and(b) the young graduates in science who are preparedat our universities and colleges, can best be utilisedin industry. Speaking broadly, the teachers ofscience do not know the needs of industry, eitherin regard to the nature of the problems whichawait solution, or to the lands of trained expertswho will be required to take part in the morehighly organised industries of the future. Again,speaking broadly, manufacturers and leaders ofindustry are equally at a loss as to the meanswhereby scientific discovery, scientific methods andscientifically trained men can be used mosteffectively in the development of the industriesfor which they are responsible.

Fortunately, there are already lines of communi-cation open between these two important bodies,and the hope for the future is that these lines maybe broadened out into a common ground on which

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mutual understanding will be reached and wherepractical schemes of development will be developed.

Much can, undoubtedly, be done to improvethe training of chemists for practical life. I t is inthe laboratory that the foundations of this trainingmust be well and truly laid by sound training andample practice mimniipulation and methods. Notonly manipulative skill, but resourcefulness and thepower of organising routine work ought to beacquired in the laboratory, if the training is on theright lines. On the foundations thus laid, a super-structure of knowledge of physical, mechanical, andchemical laws can be securely built. But ascientific equipment, however sound, is not initself sufficient; it is of equal importance that theyoung chemist throughout his training should bethoroughly imbued with the spirit and aims of thesuccessful leaders of industry. Nothing will sosurely awaken in the student an appreciation ofpractical aims as a wisely directed study of theachievements of science in industry. The presentwork will supply teachers of chemistry withabundant material for the purposes of this study.This study ought not, however, to displace theparallel study of the steps by which chemicaltheory has been evolved by the deep insight andthe patient observation and experiment of thegreat leaders in chemical science. I t ought to bemade clear to the student that, though, in one sense

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the two aims, the attainment of knowledge for itsown sake, and its attainment as a means to practicalends, are at opposite poles, yet that there is noreal antagonism between them, each is com-plementary to the other. There are intellectualtriumphs to be won in the application of scienceas well as in its pursuit for its own sake.

The deeper and more prolonged search into thophenomena and laws of Nature must, of necessity,be left to those who by natural endowment and byopportunity can pursue this search apart fromthe distractions of the work-a-day world. Theworkers on the applications of science may well,realise their debt to these seekers after knowledge,for the seeds of achievement on the practical sidemust, in many cases, be planted and watered undertheir fostering care.

"During the past three years the scientificdevelopments of modern warfare have been themeans of bringing the workers in pure and inapplied science into touch to an extent whichwould have appeared almost, iinposjsiblc in pre-wartimes. There are encouraging evidences that thisnew co-operation has been appreciated on bothsides, and that a return to the former condition ofisolation would be regarded as most unfortunate.

The authors have wisely disclaimed any attemptin this work to present the extraordinary wealth ofmaterial at their disposal hi anything like its true

WHAT INDUSTRY OWES

proportions and perspective. The precious stonesin the necklace have been strung together ratherwith an eye to their collective preservation thanto their artistic effect as a whole. Apart from thereasons for this, which the authors themselveshave given, I am inclined to think that for theserious purpose they had in view, the method hasmuch to commend it. The central object was notto present a pleasing and finished literary workwhich would gently stimulate the imagination ofthe general reader, but to set forth in their baresimplicity the broad facts of achievement, leavingeach case to make its own appeal.

In conclusion, I would express the hope thatthis work will not only be widely read by thegeneral public, but that it will be cordially welcomedby those who are most deeply concerned in thefuture of British industry.

GEORGE BEILBY.

TO CHEMICAL SCIENCE xiii

P R E F A C E .

Iisr recent times, and especially during the war,a great deal has been written and said on thebenefits derived from the applications of scienceto industry ; the subject has been discussed in thetechnical and daily Press, and in monographsdevoted to particular industries ; but, for the mostpart, it has been dealt with in the abstract or withvery limited reference to the actual results achieved.

The contents of this volume appeared as aseries of articles published in The Engineer duringthe seven months December, 1916, to July, 1917,inclusive, under the title of " What Industry Owesto Science." The articles were not intended toembrace subjects of common knowledge to theengineer, in which the influence of physical andmechanical science would have claimed greaterattention, but dealt mainly with chemical science.For that reason the title of the work has beenmodified; the text, however, remains piacticallythe same.

The object was to take each industry in turn,and to show by examples how science hadadvanced the methods and processes of production

WHAT INDUSTRY OWES

and had laid the foundation for the establishmentof new manufactures.

The work covers a survey of many importantindustries, presented in such a manner that thesubstance is not altogether out of the depth norbeyond the interest of the educated public. Wehope that it may be especially useful to students ofchemistry a]id engineering, as affording them anindication of the vast field open to them in theirprofessional careers, work in which it may beanticipated that there will be increasing activityand boundless scope in the near future ; and thatit will find a place in the offices of men of businessin many branches of commerce, and of publiccompanies concerned with productive industries,as well as in the libraries of Chambers of Commerceand Trade Associations.

A bibliography is provided, including manyuseful books referred to during the preparationof the work.

The authors desire to express their deep indebted-ness to Sir George Beilby for his kindness incontributing an introduction, which they feol hasvery greatly enhanced the value of the volume.

R. B. P.b\ B.-J.

London, 1017.

TO CHKMICAL

W H A T I N D U S T R Y O W E S T O

C H E M I C A L S C I E N C E .

CiiJLPTilR I.

MINERALS AND METALS.

WE have liL-ard a good d-'id Lit-iy of our lit-jrltx-tof science, particularly of applied science—and w»*are prepared to admit That this country h&s b-* nbehind other countries iii realising the importance <»tscientific principles in industry. The fact ivmains,however, that though we have been so remiss, we can-not have ignored science entirely, or surely tht*position of our industries—those tli&t are left to us—to-day would not h~- what it is. Ii^t'-ad of pursuingtile subjert iu the abstract, we propo.se in a i ,-w bri**fchapters to deal with accomplished facts ; to show byillustrative examples tiie extraordinary developmentsdirectly attributable to scientific thought and nittliodand the benefits derived therefrom by the community.rFl\e whole art of engineering is based on phy-?ealand riieclumical science, and the materials ernployc-din this art are dependent in borne degree o'i; ihc.science of chemistry. This country lias never lackedengineers of the first order, and, therefore, if we mayjudge by then* works, we must conclude that theirscience has been as truly founded as their structure,and their materials must likewise have been suitablefor their purpose. Clearly, then, we have not beenlacking the aid of physicists, mathematicians, andchemists hi the art of engineering and all that theterm denotes. The materials of construction t-.anr;t>tbe used intelligently unless the engineer has a proper

WHAT INDUSTRY OWES

knowledge of their physical powers of withstandingstress and strain, as well as of their chemical proper-ties, including their internal structure and power ofresistance to air, fire, water, and other agencies.

The subject is so vast and its ramifications so diversethat it is difficult to deal with it without being drawninto the production of a text-book, but we willendeavour to keep to the principal aim of showing theinfluence of science in industrial progress.

Our methods of utilising science may be wrong,and there may be room for great improvement,but the impression is gaining ground that in thehabit of decrying ourselves and our doings we haveovershot the mark. We have used science morethan we realise, but have not talked about it as muchas some other people. We know, for instance,several Sheffield steel firms who employ thirty to fortychemists and are in constant touch with the mostexperienced men of science interested in this branchof industry. We know also that both in the direc-torate and in the control of the actual processesof manufacture in the works the industry is comingmore and more under the personal supervision ofscientific men, that new laboratories are beingequipped, and that science in the steel industry isnow very much to the fore.

STEEL.German delegates to the meeting of the Iron and

Steel Institute held at Sheffield in 1905, freelyadmitted that Germany had much to learn from thatcentre and no doubt derived benefit from the hos-pitality then extended to them. The reputation ofSheffield in steel production dates from 1740,when Huntsman discovered the process of castingcompletely fused metal from crucibles. Sixtyyears ago steel was obtained by decarburising pigiron to malleable iron in a puddling furnace andsubsequently introducing the requisite amount ofcarbon by the cementation process. These operationswere protracted, required exhausting labour, andinvolved the use of large and expensive furnaces

TO CHEMICAL SCIENCE 3

subjected to considerable wear and tear and consuminglarge quantities of fuel.

In 1S56, Bessemer—a scientific mar.—as the resultof experiments deliberately directed to a definiteobject, introduced his process for **The Preparationof Steel without Fuel."' He found that by forcinga blast of atmospheric air through molten cast iron,contained in a suitable vessel lined with ganister,a siliceous material, the oxidisable impurities in theiron could be removed without the external applica-tion of heat, since the heat produced by oxidationwas sufficient to keep the mass in a molten state.Manual or mechanical stirring was unnecessary. Thepig was melted in a cupola, and transferred to a mixerof up to 600 tons capacity. From the mixer a chargewas conveyed by a ladle to the converter, the latterbeing swung into position after the w* blow " had beenstarted. In twenty minutes the operation wascompleted ; the blast was stopped for a few secondswhile a workman threw in from a shovel sufficientSpiegel or ferro-manganese to introduce the properproportions of carbon ; the blast was started againfor a short time to mix the metal and the charge wasimmediately poured into moulds.

Contrast the rapidity and simplicity of this methodwith the time and labour expended in the other.Cementation alone required seven to ten days ; theequivalent effect, after Bessemerisation, occupies onlythe time required to add the spiegel and re-mix thecharge. The fuel expended is only that used in thecupolas, and even that is obviated in some cases wherethe constancy of grade of pig from the blast-furnacescan be relied on, when the pig is takeD direct from, theblast-furnace to the converter.

The original or acid Bessemer process had, however,two disadvantages:—(1) phosphorus and sulphurcould not be removed owing to the reduction of theiroxides by iron and, therefore, only special iC Bessemerpigs," free from phosphorus and very low in sulphur,could be used; (2) the ingots produced containedblow-holes. Science overcame the first of thesedisadvantages. In 1879 Thomas and Gilchrist found

WHAT INDUSTRY OWES

that by lining a converter with burnt dolomite ormagnesite, instead of ganister, and by adding aquantity of lime to the charge, the whole of thephosphorus and some of the sulphur could be removed.

This was the result not only of scientific methodsof research but of the direct application of a scientificprinciple, viz., that of using a basic lining and addinglime, a basic material, to retain the acidic substancesproduced by the oxidation of ph.osph.orus and sulphur.The second problem, however, was solved by thoempirical discovery that the addition of a very smallquantity—5 to 8 oz. per ton—of aluminium to themolten metal minimised the formation of blow-holes.

The only important rival to the Bessemer method isthe open-hearth process, perfected about twelve yearslater by Sir William Siemens and his brother—bothscientific men. After great initial difficulties, theysucceeded in decarburising iron without contact withsolid fuel. In this process an exceedingly hightemperature is produced in an oxidising atmosphereby the combustion of a mixture of producer gas andair fed into the furnace. Changes take place of thesame character as in the Bessemer process. Bothacid and basic hearths are used, and the principle ofregenerative heating is utilised.

To Dr. Sorby, of Sheffield, we owe the introductionof metallography, and in this connection the namesof Osmond, Martens, Stead, Roberts-Austen, Sauvour,and Le Chatelier, all men of science, must be remem-bered. Up to the present day, and for some years past,the miseroscopic examination of the etched surfaces ofmetal has been common practice in steel works labora-tories. Researches on the cause of recalescence, com-bined with the intimate knowledge of the structure ofsteels afforded by miscroscopic examination, haveplaced in the clear light the equilibrium relations ofiron and carbon, and have thus changed rule-of-thumbexperience into sound scientific principle. Our viewson the physical and chemical nature of these equili-brium relations have been changed by the progress ofresearch. Explanation by means of the solution theoryhas replaced that based on the theory of the allotropy

IX) CHEMICAL SCIENCE

of iron, and our knowledge of the subject is thus be-coming more definitely established. To be able to ex-plain a phon.omon.on is second only to knowing thatiho phenomenon will occur. Whereas rule-of-thumbor empirical discoveries may occasionally give us goodresults, Hcionco, organised knowledge, enables us toproceed on definite linen.

Tho discovery of raror metals has lod to the manu-facture of many varieties of Btoel, including alloys ofapodal hardness. Tho properties of special stoolsand their behaviour under varying conditions, thebearing of tho character of their internal structureand similar questions have formed the basis ofnumorous researches which have rendered the in-dustry in an increasing degree more exact andscientific. Tho researches, of Sir Robert Hadfieldhave resulted in nupplying us with special steelsdiffering from ordinary steels, through the additionof various elements other than those commonlypresent, whereby they acquire properties of enhancedhardness, toughness, elasticity, &c.

Tims, by adding 7 to 20 per cent, of manganese woensure groat strength and toughness, the well-knownU'adlield stool ordinarily containing about 13 per cent,of manganese and 1 per cent, of carbon ; the additionof about 3 per cent, of nickel and 0.2 per cent, carbongives us a stool of tensile strength and elasticity suit-able for the manufacture of gun barrels ; and thoaddition of 2 to 3 por cent, of chromium with about1 pur cent, of combined carbon gives a remarkableBtonl which, when hardened and tornperod, is employedin tho manufacture of locomotive tiros and springs,armour platos, armour-piorcing projectiles, and certainqualities of files. Similarly, tho introduction oftitanium, molybdenum, tuugston, aluminium, vana-dium, and boron gives varying effects now easilyobtainable by the scientific steel maker.

Those examples servo to illustrate clearly thoadvantages gained by the application of scientificknowledge in tho production of one of our chiefmaterials ; but tho function of the chemists in a stoelworks or any works is not confined to devising pro-

B 2

WHAT INDUSTRY OWES

cesses or producing varieties of the products. Theyare concerned with problems of many kinds, andamong these the question of fuel and fuel economyboth in raising power and in smelting operations areof primary importance. Scioirico determines thosuitability and value of the coal employed. Tests aromade to determine the calorific power and to estimatethe sulphur, ash, and the volatile matter, includingmoisture, all important factors from tho point of viewof economy. The manufacturer who ignores thosequestions must suffer through tho employment of coalcontaining sulphur which attacks his firc-boxos, andthe purchase of water and useless mineral matter.Next, the treatment of boiler-feed water whore thosupply is not naturally soft must not be negloctod, orthe accumulation of scale will result in wasto of heat,inefficient working, and other deplorable conditions.The method of water softening, by the addition oflime, was established by Dr. Thomas Clark, Professorof Chemistry at Aberdeen University, from 1833-30,and its importance in every industry involving tho useof boilers, or requiring the use of soft water, musthave been and still is inestimable.

NON-FERROUS METALS.Mining and metallurgical industries are essentially

scientific, calling for the services of chemists (1) onthe mines, to examine ores, to advise on their concen-tration and generally to specify the methods to beadopted for the extraction of metals, and (2) in thoactual working of the metal.

The production of non-ferrous metals, such ascopper, lead, zinc and aluminium, needs tho help oftrained technologists whose labours aro constantlydirected to the discovery of improved processes and ofnew varieties of alloys adapted to special purposes,particularly those demanded by the trend of onginoer-ing development.

In surveying the history of non-ferrous metallurgy,the most striking feature is the extent of comparativelyrecent scientific advancement. In many cases themethods of treating ores to obtain crude metal

TO CHEMICAL SCIENCE

remain fundamentally tho same as when they worooriginally discovered-•••- for tho most part ompirically ;but th(\y have boon explained, modified, and improvedby science; while* in other eases, now and bettormot-hods, due solely to science, have boon substitutedfor old ones.

Thti Reparation of M/nieralx.—-The ores of heavymetals are frequently of such low grades that thometal cannot be won economically. Thousandsof tons of valuable minerals would still remainunworked except for tho scientific methods of eon-eoxxtration now eniployc^d. An ort <;ontaining onlyone \)(n- <.;ont. of tin will re-pay treatment.i t cannot bo Hmollod, but a complex procoHRof t'lablo waHhing, roasting, and wa«hing again oon-eontratoH it to d() to 70 por cont. nuidy for theHmoltor. Low grade Huly>hid< ores and graphiteoroH uni concentrated by ono or otlier of variouHmothodw of oil separation and llotation whiclx affordinteresting examples of discovery originated inempiricism, developed by chance discovery andrnochnnical ingenuity iwl further improved by thedicect application of scientific thought, whereby theirutility lias become widely extended so as to oi'footinvaluable economies iix tho minoml industries.Although various theories have boon advanced toexplain I ho phenomena of flotation, tho true mechan-ism remains as yet obscure. It is instructive tofollow tho stages of tho advances made in this direc-tion, lual to indicate the present views on tho subject.

in 1880 Carrie ,J. Kvnrson found that sulphidemineral particles could bo separated from the ganguein ores by kneading tho finely crushed ore with a pasteformed by the action of sulphuric acid on certainoils, <'"{/', linseed or cotton, send. Tho oil adhered tothe particles of sulphide mineral and bound the wholeinto a coherent mass. The ganguo was then washedaway by water. The process was very little lined, itsapplication being limited to rich, pyritic gold oroH,tho treatment of which was profitable.

Tho next development, patented by Elmoro in 1898,was an oil separation process wherein tho finely

WHAT INDUSTRY OWES

crushed sulphide ore made into a pulp with waterwas well mixed with 3 to 6 per cent, of its weightof residuum oil. The oil floated to the top andformed a layer carrying the sulphides, leaving behindthe. gangue. The top layer was separated by moansof a spitzkasten and the oil run into a centifrugalmachine containing warm water, where some of theoil was separated to be used over again. The partiallyde-oiled concentrates were further treated in a smallercentifrugal to effect a further separation of oil, andwere then ready for the smelter. In 1901 Elmorepatented the use of sulphuric acid in the process, asan aid to the production of cleaner concentrates.The process was not generally adopted because thelosses of oil due to entanglement in the gangue pulpwere very high.

The Elmore vacuum method was an outcome ofthe above. This is an oil flotation process, as distinctfrom an oil separation process. The pulp of ore andwater, mixed with a very small quantity of oil andenough sulphuric acid to make the mixture slightlyacid, is exposed to a partial vacuum; the airdissolved in the water rises up through it in the formof bubbles, floating the oiled sulphides to th© top,whence they are drawn off. From a 2 to 3 per cent,copper ore, concentrates of up to 20 per cent, canbe produced.

In 1901 C. V. Potter, working on Broken Hill ore,heated the crushed ore in an acid water pulp. Theaction of the acid upon carbonates in the ore generatedcarbonic acid gas, which, rising to tho top, carriedsulphide mineral with it. In 1902, in connection withthis process, G. D. Delprat used salt cake instead ofsulphuric acid.

In 1903 Cattermole, by adding 4 to 6 per cent,of oleic acid to the ore-water pulp and applying slowagitation, caused the sulphide particles to aggregateinto large granules with the oil. The gangue whichremained in the pulp was then separated by moansof an up-cast. The principle of the method was good,but the expense in oil was large. It was in connectionwith the work on this process, however, that the froth

TO CHEMICAL SCIEHCE

flotation process was discovered. fey; usin jtities of oil—up to 0.1 per cent, .calculated on"tne*ore*though less generally—and chumirig up the pulp withair by rapid agitation with a special pa^Lle, the oiledsulphide particles are caused to rise .to^utye^pp^pastrong froth which is floated off by a spitiak^steprocess especially has been developed by sciensearch, and the efficiency and the economy of ore con-centration have been thereby greatly improved. Sul-phide ores of zinc, copper, lead, iron, antimony,molybdenum, and of other metals are very efficientlytreated. Tin-stone-pyrites table concentrates arcseparated, the pyrites being floated oft*; and graphiteis easily concentrated to an exceedingly clean product.The grade of the concentrates is high and the recoveryexcellent. The use of acid is sometimes necessaryto produce clean concentrates, enough being addedto ensure an acid reaction in the pulp. Curves can bep]otted showing the variations in. grade of concen-trates and recovery with variation in the amounts ofoil and acid used. The testing of ores is scientificallycarried out in special apparatus. The experimenternot only finds the best method for treating the ore,but also observes and records any peculiarities ex-hibited that m&y be of use in furthering the aims ofthe process or may serve to throw light on theultimate causes of the principles underlying themethod. Wood's modification of the above processrenders it possible to concentrate certain ores withoutthe use of oil.

These concentration processes aro of comparativelyrecent invention, and are increasingly applied to thetreatment of low grade sulphide ores and the tailingsfrom table concentrations.

Experiments on the notation of other minerals,such as native copper, gold, and Scheelite, an ore oftungsten, havo met with success, and will probablybe greatly developed during the next few years. Theflotation of carbonate and other oxidised ores hasbeen attempted with positive results, but this exten-sion also is as yet in the experimental stago. Thegeneral opinion of mon of science at the present day

1M WHAT INDUSTRY OWES

is that flotation is an effect of surface tension, thoughsome favour the view that the mineral particles mustalso carry a:, electric charge. The ultimate causescan crJy be established by further research.

In dealir.g with the separation of minerals we shouldmention also rhe important work of electrical andmechanical engineers,^to whom much credit is due forthe invention" of magnetic separators. Many orescontaining magnetic minerals are now efficientlytreated hy these machines, involving both wet and drymethods." As instances may be taken the magneticconcentration of magnetite ores, and the separationof this mineral from pyrites. Magnetic separationhas also been applied in the treatment of monazitesands for the concentration of thorium, to which wewill refer later.

Copper.—Scientific knowledge has come to the aidof the copper smelter and refiner in various ways. Theintroduction of water-jacketed blast furnaces—suchas are used in lead smelting—in the fusion for regulus,has reduced wear and tear to the minimum. Thesefurnaces are made of iron and are double walled, withwater circulating through the space between thewalls, producing a cooling effect inside the furnace inthe ininiediate vicinity of the wall. The result isthat some of the molten slag solidifies on the wall,forming a protective coating which is not furtherattacked, since the liquid does not corrode it, andthus the iron walls of the furnace scarcely come intocontact with the liquid.

A method of smelting pyritic copper, silver, or goldores by the heat of oxidation of the pyrites, withoutthe aid of any other fuel was introduced as recentlyas 1905 ; in actual practice, however, up to 5 per cent,of carbonaceous fuel is now added. Water-jacketedblast furnaces are used, and air—pre-heated in somecases—is liberally supplied through a large numberof tuyeres.

Copper intended for use as an electrical conductormust be of high quality, the presence of very smallquantities of certain other bodies causing a markeddiminution in its efficiency. The necessary degree of


purity can now easily be obtained by the methods ofelectrolytic refining. A thin sheet of electrolyticcopper forms the cathode, a slab of blister copperthe anode, and the electrolyte is an acidified solutionof copper sulphate.

Pure copper is deposited on the cathode, the anodebeing gradually dissolved. Impurities in the copper,such as iron, zinc, nickel, &c., of which the sulphatesare soluble, are allowed to accumulate in the solutionuntil their quantity renders the liquor inconvenientto deal with. At this stage the copper in the liquoris precipitated with metallic iron and fresh solutionsubstituted. Other metals present, such as platinum,gold, silver, lead, and arsenic, form a fine mud in thebath, and this mud is afterwards treated for recoveryof the precious metals. Thus, by this scientificmethod, not only is copper obtained in a very purestate, but the gold, silver, and platinum also can beextracted profitably.

Lead.—A remarkable instance of the application ofpure science to the solution of a technical problem isprovided in the methods employed in the desilverisa-tion of lead by the Pattinson and the Parkes methods.Before 1833 the only available process was cupellation,and this could only be effected economically if the leadcontained 8 oz. per ton or more of silver. Thereforemuch silver remained in the lead, of which, in theaggregate, large quantities contained less than thisamount. The method patented by Hugh LeePattinson in 1833 depended on the fact that whena solution is partially frozen some of the solventseparates in the solid form, leaving a solution richerin the dissolved substance. For instance, when saltwater is frozen, pure ice separates and the remainingsolution is stronger in salt. Molten lead containingsilver may be regarded as a solution of silver in lead,and if this solution is allowed to solidify partially,almost pure lead separates out in crystals. Twomethods are adopted, that of thirds and that ofeighths. Usually, sixteen kettles, lined with lime toprevent attack by litharge and holding about 12 tonseach, are employed. For lead comparatively rich in

12 WHAT INDUSTRY OWES

silver, two-thirds of the contents of each pot areremoved as lead crystals ; and for lead which ispoorer in silver, seven-eighths of the contents isremoved from each pot. In the latter case fewerpots are required. By these means, respectively,starting from a lead containing up to 3 oz. of silverper ton, a silvery lead containing 700 oz. per ton,and a " pure " lead containing only £ oz. to J oz. ofsilver per ton can be obtained. The process in eachcase is stopped when the silver reaches about 700 oz.per ton, as this is approaching the eutectic* Amodification of the method nas "been introducedwhereby the lead is cooled more quickly by blowingin steam and spraying the top of the lead with coldwater, the rich silvery lead being poured off from thecrystals instead of the latter being baled out.

The silvery lead obtained by either process iscupelled on a hearth made partially of bone ash,which absorbs most of the lead oxide. Some of thelitharge produced is blown over the side of the cupelby the blast of air, and is used in the manufacture ofpaint.

The Parkes process depends upon the fact thatsilver is much more soluble in zinc than it is in lead,whilst lead and zinc are mutually soluble only to asmall extent. A saturated solution of zinc in leadcontains only about 1 per cent, of zinc whilst asaturated solution of lead in zinc contains 2 to 3 percent, of lead. If, therefore, molten argentiferous leadis stirred up with molten zinc the latter extracts mostof the silver from the lead and when the stirring isdiscontinued rises to the top, forming a separate layer.An exactly parallel operation frequently used in thelaboratory is the method of extraction by ether.On shaking ether and water together each dissolves alittle of the other. When the shaking is stopped theliquids separate into two layers, the ether being theuppermost. Suppose we are dealing with the aqueoussolution of a substance that is more soluble in etherthan in water, and that the solution in water isinconvenient to work with, the substance can be

* Seo note on p. 21.


almost completely removed as a solution in ether byshaking the solution repeatedly with small quantitiesof ether, which can then be removed by distillation.

In practice, the work lead is purified by remelting,to effect the removal of copper, arsenic, antimony, &c.The lead, so far purified, is then melted in a potand heated to about 500 dog. C, lumps of zinc areadded and the liquid is well stirred with iron paddles.The quantity of zinc added depends on the richnessof the lead in silver, but in any case is very small andrarely exceeds 2 por cent, of the weight of the lead.When the agitation is stopped, the liquid is allowed tocool and a crust of zinc containing the silver solidifieson top of the still molten lead, is removed by ladlesand liquated to separate some of the zinc. Theremainder of the zinc-silver mixture is then transferredto graphite retorts and the zinc is distilled off. It isfound to be advantageous in extraction by zinc—as inthe case of ether—to add the zinc in three instalments,and not all at once. When the lead contains gold,about one-tenth of the zinc is put in at first, when thescum of zinc separated contains all the gold. Thesilver is then extracted by continuing the process.The remaining lead contains about 1 per cent, ofzinc, which is removed by blowing air and steamthrough the molten metal, the zinc being blown awayas oxide, leaving the lead in a very pure state. TheParkes process, now used extensively, has beenrendered more efficient by the recent discovery thatgraphite retorts can be used for the distillation of thezinc.

These processes for desilverisation not only yieldvaluable quantities of silver but also produce leadin a high state of purity. In fact, lead as now pro-duced is one of the purest of the commercial metals.It would probably not be so if no precious metalcould be extracted from it, because in order to winthe silver all other impurities must also be removed.Whereas work lead is hard, pure lead is soft and canbe easily manipulated, purity being, moreover, veryimportant in the starting material for the manufac-ture of white lead for making paint.


Xickel was discovered by Cronstedt in 1750-During recent years it has assumed an importantposition in. the civilised world. It is malleable,ductile, hard, takes a high polish, and is veryresistant to atmospheric oxidation. To thesevaluable properties nickel owes its use in the electro-plating of small iron and steel articles to preventrusting, in the manufacture of rifle bullets, which arecovered with a layer of nickel to give a hard cleansurface that will not foul the barrel, and also in thepreparation of nickel steels and of certain alloyswith copper and zinc, such as nickel silver, whichare used in the manufacture of forks and spools,ornamental articles, wire, medals, and coins. Nickelis also used in the finely divided state as a catalyst,in the hydrogenation of certain, oils and fats- By theaction of hydrogen in the presence of finely dividednickel, liquid oils such as fish oil, Unseed oil, olive oil,can be ci hardened " into solid fats suitable for thestarting materials in the manufacture of foodstuffs,candles, and soap. For these purposes the nickelused must be very pure. The older methods of pro-duction were difficult and expensive, but in 1895Ludwig IVIond introduced a method by which thepure metal can be obtained at a comparatively lowcost from the matte produced by the first smeltingoperation. Mond discovered that metallic nickelcombines with carbon monoxide when heated to80 deg. C. in an atmosphere of that gas, yieldinga volatile compound, nickel carbonyl. The matte isroasted and then reduced at 400 deg. C« byproducer gas. The reduced metal is then exposedat SO deg. C. in a " volatiliser" to the action ofcarbon monoxide. The gas issuing from the volatilisercontaining the nickel carbonyl is passed throughvessels heated to 180 deg. C, where the nickel isdeposited in the pure state. The carbon monoxideis obtained from flue gases by passing first throughboiling potassium carbonate solution and then overhot coke. The carbon monoxide obtained by thedecomposition of the nickel carbonyl at 180 deg. C.is also used over again. This brief survey shows how


Mond's scientific discovery and its exploitation hashad its effect on very diverse industries.

Sodium.—Metallic sodium was first obtained by SirHumphry Davy, in 1807, by the electrolysis of causticsoda, but no attempt was then made to manufacturesodium on the large scale by that process. Up to 1891it was produced by carbon reduction methods. Themethod of Brunner, improved by Deville, consisted inigniting a mixture of sodium carbonate and charcoal;but this process was very wasteful and expensive,and the price of sodium was consequently high.In 1886 Castner employed caustic soda instead ofsodium carbonate, and this improvement, the outcomeof scientific research, effected substantial decrease inthe cost of production. In 1891 the old process wasentirely abandoned and replaced by Castner's electro-lytic method, founded on Davy's discovery anddeveloped in the laboratory, by which fused causticsoda was electrolysed in an iron vessel under specialprecautions for even heating and the maintenance ofa cpnstant temperature. The method was cleanerand more efficient, and as a result sodium became reallya commercial product,. thousands of tons being ren-dered available annually for the preparation of sodiumcyanide for gold extraction, under the MacArthur-Forrest process for dealing with low grade ores andsand and slime tailings.

Aluminium—so much valued for its lightness,strength, and unalterability in air—has a historyresembling that of sodium. It was first isolated in thepure state in 1827 by Wohler. by fusing the chlorideof the metal with potassium in a closed crucible, andagain by the same chemist by passing the vapour ofaluminium chloride over potassium. In 1854 Bunsenused the method of electrolysis of the fused chloride,and Deville applied the method of Wohler in attemptsto manufacture the metal on a large scale usingsodium instead of potassium. Samples of Deville's pro-ducts were shown in ingots at the Paris Exhibition of1855, where they occupied a prominent position, care-fully guarded by gendarmes, only a few visitors beingallowed to handle the exhibit, which was regarded as


a great curiosity. This was an incentive to furtherresearch, with the result that a short time later tholarge scale manufacture was established at AJais onthe Loire. The use of sodium, then itself a costlymetal, was only one itom in the heavy expenseinvolved. The' method held its own for some years,but in 1887 Bernard Freres, of Paris, revertingto the method of Bunsen, foundod their electro-lytic process, using a mixture of cryolite andcommon salt as the electrolyte. Before 1887aluminum was sold at £3 per pound. Now it can bo madoat very low cost, where power is cheap, to bo sold atlittle more than a shilling per pound. Tho methodwhereby a solution of oxide of aluminium in fusedcryolite is kept in the molten state, and decomposed,by an electric current, yields a metal of over 99 percent, purity compared with the 97 to 98 per cent,metal from the older process. Tho expenditure ofelectrical energy is high, and in the light of ourpresent knowledge it appears futile to endea-vour to reduce it. When aluminium is used inthe thermite process, an enormous quantity of energyis evolved in the form of heat, producing a very hightemperature, the aluminium being converted into theoxide. To win back the metal from the oxide anequal amount of energy has to be put back, thusaccounting for the quantity of energy absorbed inthe preparation of the metal.

Magnesium was first isolated by Davy. It owes itsmethod of preparation and prosont-day uses solely toscientific investigation. It is manufactured by a pro-cess similar to that used for aluminium, by the electro-lysis of fused anhydrous carnallito, a double chlorido ofmagnesium and potassium. The " magnalium"alloys of aluminium and magnesium are lighter thanthe former metal, give very good castings, and arcas strong as brass and bronze. Tho use of magnesiumin flashlight photography is well known.

Molybdenum and Tungsten, like aluminium andmagnesium, are children of science. Both are usedfor making special steels, and tungsten is also formed


!^° filaments for incandescent electric lamps, its-wcienCy i n this role being very great.Jphromium, which was discovered by Vauquelin in'97, and is much used in the manufacture of special:esl has a very high melting point, and on that

cannot be prepared in a fused state byy methods. The metal was isolated byby heating chromium oxide and sugar char-

in a lime crucible ; and by Wohler by hoatingchloride with metallic zinc under a layer of

chloride, and subsequently removing theby treatment with nitric acid, the chromiumthereby obtained in the form of a grey powder ;

ut these and similar methods could not be adopted'°p.omically on a commercial scale. In 1893;°issan published the method whereby a mixture• chromium oxide and carbon is heated to the hightfxiperature of the electric furnace, giving a productstaining large quantities of carbon from which itw* be freed only by difficult and expensive processes,errochrorne, however, an alloy of iron containing 60> 70 per cent, of chrornium, is manufactured on a•rge scale by the thermite process. Chromite, an•fc of chromium and iron, is finely crushed and wellixed with aluminium dust. The mixture is ignitedith the aid of burning magnesium. The aluminium>duces the oxides of iron and chromium with evolu-oxi of great heat, and consequent production of a»mperature sufficiently high to fuse tho ferrochrome,ie alloy being thus produced in a compact and3mogeneous condition. Chromium metal of over). 5 per cent, purity can be obtained by the thermiterocess, the principal impurities being small quanti-es of iron and silicon. The thermite process is usedhen freedom from carbon is desired, that of Moissan3ing applicable when tho presence of a certain.lantity of carbon is not objectionable.Thorium, discovered by Berzelius in 1828, is

.teresting scientifically by reason of its radioactivity.> has found no useful application as a metal, but itstide, thoria, has proved invaluable to the gas.dustry, being used for th© manufacture of incan-

IS WHAT INDUSTRY OWES

descent mantles, of which the world's production isestimated at over 400,000,000 annually. Thoria,when heated directly in a flame, possesses the propertyof converting heat energy into light. Research wastherefore directed to the utilisation of this property,the evolution of the modern gas mantle being theresult of purely scientific investigations, requiringgreat skill and patience. Not the least difficult pro-blem to be solved was the production of thoria inthe necessary state of purity. In the early historyof the manufacture of the mantles, the known sourcesof thoria were not numerous, although the availableores were rich, and presented little difficulty in treat-ment, but the discovery of large deposits of monazitesand in South America stimulated the industry byconsiderably duninishing the cost of the materialsemployed. For a time, while the value of the sandremained unrecognised by the States wherein it wasfound, the sand was shipped to Europe as ballast—anillustration of the advantages to be gained fromscientific investigation into natural resources. How-ever, that is another story ! Monazite is a complexmineral consisting of the phosphates of thorium andthe metals of the rare earths, occurring mixed withother minerals as a sand. To obtain pure thoriafrom this ore a protracted treatment is necessary,involving concentration by tables and by magneticseparation, followed by fractional precipitation ofthe oxides from solution. The thoria appears on themarket as nitrate. In the manufacture of mantlesa cotton framework, supported on an asbestos collar,is soaked with a solution of the nitrate and dried ; thecotton is burned away, and the resultant oxide ishardened by further heating, and stiffened by dippinginto collodion, which in turn is removed by burningwhen the mantle is placed in position ready for use.It was found that the presence of about one per cent, ofcerium oxide in the mantle increased to a maximumthe transformation of heat energy into light, whereasa marked diminution of luminosity was observedwhen the quantity of cerium oxide was increased ordiminished. For this reason the equivalent of one

TO CHEMICAL SCIENCE?

per cent, of cerium oxide is added to t h e solution ofthorium nitrato. Tho credit for practically the wholeof the scientific work underlying tho industry is dueto Auor von Welsbach.

Vanadium, discovered in 1830 by Sofstrom, in therefinery slag of tho iron oro of Taborg, in Sweden, isof increasing service to tho maker of special steels.In ofToct 0.2 per cent, is equivalent to 3 t o 4 per cent,of nickol, and exporionco toads to show t h a t it impartsto stool tho power of resisting changes caused byvibration, a most valuable property from the engi-neer's point of viow. It is mainly used as an alloy,forrovanadium, prepared by tho thermite process.It is worthy of note, as affording an instance of theutilisation of " waste," that tho mixture of metalsobtained by reducing tho rare earth oxides formingthe rosiduo of monazito aftor tho extraction of thoriais employed, in the placo of aluminium, to producepuro vanadium by a method resembling t h e thermiteprocess.

THE NOBLE METALS.Gold.—In tho rocovory of gold large quantities

of motal wore previously thrown away in tailings,owing to tho fact that amalgamation loft a certainamount unoxtractod from tho oro. The Plattnerchlorine method and tho MacArthur-Forrest cyanideprocess havo now rendered tho tailing metalavailable. Tho Plattnor method, which is also usedin tho treatment of auriferous pyrites, dopends on theaction of chlorine gas on tho roasted oro, t h e chlorideproduced being subsequently loachod out with water.Tho gold is thon precipitated by treating t h e solutionwith some suitable material, such an ferrous sulphate,charcoal, sulphuretted hydrogen, sulphide of iron, orsulphide of ooppor. Tho MacArthur-Forrest pro-cess, also fouudod on tho study of the chemicalproperties of gold, consists in tho treatment of thesand or slimo tailings from tho amalgamationprocess, or, in some cases, a very low grade ore,with a dilute solution, not more than 0.3 per cent.,of potassium or sodium eyanido, and the subsequent

o


precipitation of the dissolved gold by means of zincshavings. The zinc is removed hy distilla/fcion fromgraphite retorts, or sometimes by dissolution insulphuric acid, the latter method yielding a somewhat

. richer bullion. In a method introduced b y Tavener,the zinc-gold precipitate is mixed with litharge, saw-dust and assay slags, and melted in a reverberatory,the resultant lead bullion being subsequently cupelledfor recovery of the gold. In. another method,devised by Siemens and Halske, the gold i s precipi-tated from the cyanide solution by electrolysis, usingiron anodes and lead cathodes and recovering thegold by cupelling the cathodes.

In the separation of gold from silver, nitric acidwas at one time universally employed, biat in 1802D'Arcet utilised the fact, discovered in. 1753 byScheele, that concentrated sulphuric acid w a s equallysuitable for the purpose. This constituted a n improve-ment of considerable value, effecting a saving both ofcost and time, and it must be remembered t h a t in thisconnection " time is money," for gold brings interest.

The Platinum Group.—The metals of the plati-num group are among the most valuable acqui-sitions of civilised man, and their availability isentirely due to chemists, among whom may bementioned Achard, Janetty, Knight, Wollaston,Deville, and the firm of Johnson, Matthey and Co.Platinum itself is easily worked by the oxy-hydrogenflame method of Hare, modified and improved byDeville and Debray, and is useful for many purposesin which special resistant properties are essential,such as for vessels employed in analytical chemistry,for stills for the concentration of chamber acid,for standard weights and measures, for electricalleads fused into glass, as a catalyst in t h e contactprocess for making sulphuric acid, as a photographicmedium, and for mounting jewellery.

Other members of the group are indium, discoveredby Tennant in 1804, used in combination with plati-num in the construction of pyrometers, a n d as puremetal for tipping gold pens ; osmium, discovered byDeseotils in 1803, and by Tennant in 1804, used in the


preparation of metallic filaments of electric lamps,and combined with iridium for tipping gold pens andfor tho bearings of tho mariner's compass ; palladiumdiscovered by Wollastoh in 1803, employed bydentists and jewellers ; and rhodium, discovered byWollaston in 1804, UKOCI in tho mamifactxire of certainforms of ehomical apparatus.

IO (p. 12).—An alloy in tonnod outoctic when it is themost/ fusiblo of the alloys of two metals, the meltingpoint boing lower than that of either of the twometals of which it is composed. On cooling from themolten atato il doponitH a rtolid having tlio same com-poHition as that, of tho moltim mixture. For example,tho molting points of load and tin are 328 and 232 deg.Con I. roapoctivoly, but an alloy of those motals containing31 per cent, of load melts at 180 dog. Cont., any variationfrom this composition entailing a rieo in the melting point.If an alloy richer in oit.hor eonBiii/uont ho slowly cooled, themotal proaonfc in OXOOKH of tlio above composition separatesin tho Holid st.al-o an cooling prcjgi'OSHOfl, until the composi-tion of tho remaining lluid in that of the eiatectic, whichtlion so]_Dftratos in tho Holid Htato. In tlio case of alloys ofgold and nilvor tlioro is no outoctic, tho inelting pointsrising regularly from that of silvor to that of gold.


CHAPTER II.

HEAVY CHEMICALS AND ALKALI.

IN reviewing the progress made in chemicalindustries proper, we are met with such a conditionof interdependence that it is impossible to avoid over-lapping of the subjects to be treated. Moreover,the steps made in the improvement and developmentof processes, and in the evolution of new products,are so numerous that space will not allow of a com-prehensive scheme. Indeed, the library of t he Patent -office, one of the best for technological literature,cannot contain all that is due to chemists, nor discloseto which chemists the credit should be given for manyimportant advances. We must, perforce, recognise,however, that science is the basis of all substantialdevelopment in the industrial arts, and that the ruleof thumb is dead.

It has often been said that the prosperity of acountry might be gauged by its output of sul-phuric acid ; yet it is remarkable how littlethe man in the street realises the importance ofthis substance. He has a vague idea t l i a t it isthe same thing as, or in some way akin t o , vitriol,which he knows is destructive to clothing, and isassociated with charges of criminal assault whereinsome evil-minded wretch has employed i t as theagency for disfiguring the features of a fellow-being.If he were told that, even in normal times, t h e world'soutput exceeded 5,000,000 tons he would, marvelhow it is that he never sees, and probably neverhas seen, the substance. The reason for this is,that the consumer of large quantities of tlie acidgenerally finds it convenient and economical t o makeit himself. Thus, although large quantities areproduced and consumed there is only a comparatively


small quantity on the market. When we cometo consider its technical applications we find thereis scarcely an industry that does not depend directlyor indirectly on its use. It is employed in themanufacture of superphosphate fortilisor, as a solventfor metals—for example, in, the parting of goldand silver—as a constituent of dipping baths forcleansing brass and bronze castings, and is usedin tho electrolytic refining of copper. Ammoniafrom tho coal-tar and shalo oil industries is absorbedin sulphuric acid, the resultant sulphate being exten-sively omployod as a fertiliser. (The world'sproduction of ammonium sulphate probably exceeds1,500,000 tons.) The refining of oils, fats, and waxes,and of tar and petroleum products is also carried outwith the aid of sulphuric acid, and it is extensivelyused in the manufacture and sulphonation of dyestuffs.Nitric acid, guncotton—and thorofore, cordite, collo-dion and celluloid—nitroglycerine for dynamite,phenol, picric acid, T.N.T., other, saccharine, manydrugs, liquid gluo, alum, porsulphates, and a hostof other useful Bubstancos are produced by processesin which sulphuric acid is an essential factor. I tmust be remembered, moreover, that many suchsubstances are but tho starting materials for themanufacture) of other products ; so that regardedas a modiamil ancestor, sulphuric acid can boasta genealogical tree of no moan order with manya noble family and innumerable progony. Normust we forgot that not the least important of its usesis in the laboratory, whore also many of its relationsarc to bo found among tho roagents required bythe chemist. Discovered in the fifteenth centuryby the alchemists, it WUR made until about 1770by two methods : (i.) by tho distillation of crystallisedsulphato of iron prepared by roasting iron pyrites ;and (ii.) by tho combustion of sulphur in a bell jarover water. Of these methods, tho first surviveduntil recently, boing the only method availablefor making fuming acid, tho second being the fore-runner of the modern load chamber process. Bothare attributed to Basil Valentino (15th century),


who next discovered that by the addition of antimonysulphide and nitre, the yield could be substantiallyincreased. Up to about the middle of the eighteenthcentury the principal workers at the problem hadbeen alchemists—monks and others—the pioneersof modern science ; and the only process t l ia t couldbe called a manufacture was that with sulphate ofiron as starting material. At about t h a t time,however, two French chemists, Xefevre and. Lemery,produeed_a method, used on a small maniif acturingscale, wherein a mixture of sulphur and nitre, withoutantimony sulphide, was burned under a, bell-jarover water. About 1770 Dr. Roebuck, of Birmingham,first employed lead chambers containing water,instead of glass bell-jars, thus considerably enlargingthe scale of operations. The procedure was the sameas in the bell-jar method. The floor of the leadchamber was covered with a few inches of -water, anda kind of stand in the middle of the floor carried thecharge of sulphur and nitre. The charge w a s ignitedai.d the door was immediately closed a n d lutedsecurely. The operations of charging, bcurning, anddischarging were repeated until the acid, attainedthe maximum strength compatible with t l ie safetyof the lead, when the liquid was drawn oE a n d concen-trated. This was a discontinuous process, but inprinciple it was the modern continuous methodin a primitive state. The transition from the oneto the other was gradual, the outcome of muchthought and research. A step towards continuityof working was obtained by burning t l ie sulphurin a separate vessel, and leading into the lead, chamberthe products of combustion, mixed with excess ofair, and the fumes evolved on treating nitre withsulphuric acid. Complete continuity a n d greaterspeed of working was obtained when Kestmer intro-duced the injection of steam into the chamber.The rationale of the process was explained b y chemistsby the aid of various theories, but a fact of greatimportance was clearly recognised, viz., that thenitric acid was merely a carrier of the atmosphericoxygen, and needed to be used only in small quantity.


Next it was found that the spent gas issuing fromthe chambor gave rise, in contact with atmosphericair, to oxidised nitrogen compounds that could beused again in the chambor. Nitre being the mostoxpensivo raw material, many efforts were directedtowards tho recovory of those gases and their returnto the circuit. Tho most successful of these andtho one universally adoptod was duo to the greatFrench chmniut, Gay-Lussac, tho friendly rivalin many fields of work of our own Sir HumphryDavy. Tho gasos issuing from tho chamber wereconducted up a tower of load or stone, packed withcoke, down which a Blow stream of strong sulphuricacid was caused to trickle. The acid issuing fromthe foot of the towor contained all tho oxides ofnitrogen present in tho chamber gas. This acidwas thon convoyed to tho top of another tower,inventod by Glover, and in penetrating the lengthof the towor was mot by tho hot gases from the sulphurburners and doprivod of its nitrogen oxides whichwore returnod to tho chambor with the ingoing gases,to play again thoir part in the transformation. Theacid drawn from tho chambor was concentratedin glass retorts, platinum being afterwards substitutedfor glass. Although tho initial outlay on platinumwas very considerable, the loss by breakage wasavoided.

Thin short history of sulphuric acid manufacturefthould sorvo to illustrate how Kcionco has been, theprimary factor in its evolution. The subject of thevise of iron pyritos as a sourco of sulphur will bedeferred until wo consider tho alkali industry. ,

We must digross for a moment to refer to anotherindustry in ordor to indicate the origin of the contactprocess. About thirty-six years ago, various methodswore discover od for the preparation of artificialindigo, and endeavours wore made to apply the bestof those on a commorcial scale to compete withthe natural product. Tho starting material in themost successful processes was naphthalene, at onetime rogardod by tho tar distiller as a nuisancebut now recognised as a valuable product. In the


first stage of the synthesis of indigo, naphthaleneis converted by oxidation into phthalic acid. Thiswas originally effected by chlorination and subsequentoxidation with nitric acid; but the process was tooexpensive for successful application on the largescale. Next the discovery was made that the directoxidation of naphthalene could easily be effectedby fuming sulphuric acid in the presence of mercuricsulphate. At that time, however, the only methodof preparing the fuming acid was the Nordhausenprocess, by heating sulphate of iron, and the productwas too highly priced for the prospective indigomanufacturer. Cheap fuming acid was, therefore,a necessity. It had been known to chemists fora half a century or more that sulphuric acid anhydridecould be made from sulphur dioxide and oxygonby passing the mixed gases over heated finely dividedplatinum, and it was found that by absorbing theanhydride in concentrated sulphuric acid the productwas the fuming acid. In the laboratory, wherethe materials employed were comparatively pure,the method left nothing to be desired, but on theworks where, for reasons of economy, materials ofa crude nature, such as pyrites, had to be used,further obstacles were encountered. The processwould go briskly for a time and then it would slowup and finally stop altogether. The platinum hadlost its efficiency and the chemists were confrontedwith another difficulty. They are accustomed tothis sort of thing and enjoy it. Indeed, some arealmost disappointed when results come too easilyand there is a lull in the chase. They found thatthe platinum had been " poisoned" by arsenic,antimony and mercury from the pyrites ; they there-fore devised the~ means for washing these oxidesout of the sulphur dioxide, and with this purifiedmaterial their labours were crowned with success.The manufacture of fuming acid and ordinary con-centrated sulphuric acid by the " contact process "is a fast growing industry, and will doubtless intime largely replace the lead chamber process byreason of its efficiency and cleanliness, and the


compactness of tho plant required. Moreover, itis convenient and economical to bo able t o produceacid of any strength without tho expense involvedin tho concentration, n,ooossary in tho older process.On account of tho diversity of its uses sulphuricacid is required in varying conditions of purity andconcentration, from tho chamber acid a.ndL B.O.V.of cominorco to tho redistilled acid required inanalytical operations. Researches have been con-ducted with a viow to tho elimination of impurities,and especially of arsenic. Tho contact processsatisfies this requirement, but acid from tho chamberprocess may contain this impurity in considerablequantity. The use of sulphur instead of pyritesresults in the production of arsenic free acid,but chamber acid already containing arsenic canbo freed from this impurity by precipitating it assulphide with sulphuretted hydrogon before con-centrating tho acid. Another method has beensuggested whereby dry hydrogen chloride is passedthrough strong sulphuric acid heated above 150 deg.Cent., when tho arsenic is entirely removed astrichloride, but this has not received extensiveapplication. Both those methods arc founded onoveryday laboratory oxporioneo.

Ono hundred and thirty years ago, as a resultof tho French revolutionary wars, France was cutoff from the supply of alkali and an appeal wasmade to ehomiBts " to render vain the effortsand hatred of despots," and, incidentally, to wina prize by producing a process for making alkali.This offer resulted, in 1794, in tho submission to theConvention of moro than a dozen processes, some ofwhich had already boon in operation, including thatof tho apothecary Leblnno, which was accepted. In1814 it was introduced into England, and in 1823 thefirst works of importance worn osi.ublishod near Liver-pool by J'ameH Muspmtt-. In tho LeblancJprocesssulphuric, acid is employed for tho decomposition ofcommon, salt. Tho resulting sulphate is hoated withchalk and small coal in, a. rovorboratory furnace ; themass is lixiviated with cold, or tepid water; the


solution is evaporated to dryness and the productis calcined with sawdust in a suitable furnace. Thesoda-ash or crude sodium carbonate thus obtainedis dissolved in hot water, treated with lime, to obtaincaustic soda, to be used by the soap and candlemakers,or the solution of the carbonate in water is filteredand crystallised to give washing soda. We haveindicated that the substances required for theprocess were salt, coal, chalk, and sulphuric acid.The first three were to be found in abundance inNature, but up to that time sulphuric acid wascomparatively expensive, and the demand for itwas not such as to warrant its extensive manufacture.It was to meet the requirements of the Loblancprocess that the output of the acid was enormouslyincreased, and although the process has now beensuperseded by that of Solvay, as far as carbonate isconcerned, and is being replaced by electrolyticmethods for making caustic soda, it must not be over-looked that we owe to Leblanc, indirectly, our cheapsulphuric acid, and therefore a thousand and oneother cheap commodities.

To return- to the sodium carbonate, we may wellask how many good citizens and washerwomenwho use it have any idea that a chemist has anythingto do with its production ? Possibly they thinkit exists naturally in the condition supplied; moreprobably still, they think nothing at all about itso long as it serves its purpose.

If the crystals are re-dissolved in water, filteredand re-crystallised, we have the pure sodium carbonateused in pharmacy. By passing carbonic acid gasinto a cold solution of the carbonate, and by placingthe crystals in an atmosphere of the gas, we obtainthe bi-carbonate which is also employed in pharmacy,and as an ingredient of baking powders.

The aim of the technologist is- to avoid wasteof any kind, either oi matter or energy, the costof a product to the consumer being in a great degreedependent on the efficient utilisation both of rawmaterial and of by-products. The alkali industryfurnishes many examples. In the Leblanc process,


among the main products are soda ash , which wo havoshown is purified to obtain soda crystals, arid c alkaliwaste," of which about 30 per cent- is calcium milpbidr,containing the sulphur from tho original Hulphunoacid. The waste was long regarded an UHOIOHK, hut JHnow treated for the recovery of tho sulphur. Manyattempts have been made to recovor tlu'H sulpUur ina useful form, but it was only compare tivoly nw.onUythat the Chance-Claus method w i s mtrodiu:o<l,whereby the alkali waste is mado in to n panto wU.hwater, and acted on by carbonic acid gan -limo-kUugas and furnace gas being used for tlu> ptirpoHo.The sulphur of the calcium sulphido in convortodthereby into sulphuretted hydrogen, which I'M mixodwith a carefully regulated supply of air and burnodin contact with hot ferric oxide in ClauH kilnn. Thohydrogen burns off and the sulphur is dopomtodin a practically pure state—a very vn.lua.blo product.

When, in 1839, an export embargo wan plaeodon Sicilian sulphur, the alkali mamrfactumrK, havingto look elsewhere for their supply, found it in ironpyrites. The residue of oxide of iron from tho pyritowburners was not used as a source of i ron, an it rotninodenough sulphur to render it unfit for thin purpono.Tho pyrites used also contained a cor (.am amountof copper,-averaging 3 per cent., a« woll UH Hmn.llquantities of gold and silver. Un t i l 18(15 thoHoresidues were dumped as useless, b u t in that, yourHenderson introduced a method whoroby tUo whoh^of the copper could be recovered b y roasting thoresidues with common salt, lixiviating tlio tauHHwith water, and precipitating tho coppor from thoresultant solution by means of scrap iron. In 1870,a method was devised by Claudot t o rocovor tho goldand silver occurring in the rosiduoB- Tin) <?<>pporsolution formed, on lixiviation in FCoxMlormn'i* proooHHcontains the gold and silver as cliloritltw cliHwolvo<lin the excess of common salt. By Ohvudot'M mothodthe gold and silver are precipitated, by tho additionof zinc iodide to this solution, tlio prooipifcatodiodides being subsequently reduced, with motulliozinc^in the presence of hydrochloric acsicl.


Thus by the application of science the revenueof the sulphuric acid and alkali maker increased,the price of his products is lowered, and valuablematerials are rescued from the dump. Morethan 500,000 tons of pyrites are burned annuallyin England for the sake of the sulphur. The residuefrom this yields on extraction aboiit 15,000 tons ofcopper, 400,000 ounces of silver, and 2000 ouncesof gold, the final residue being transformed into avaluable source of iron.

In connection with this subject can bo related oneof the most interesting episodes in industrial history.For some time after the inception of the Leblancprocess, the hydrochloric acid produced was allowedto escape into the air, as no use had been found forit. Metal ware was corroded, and vegetable growthdestroyed for miles around the works and the nuisancegave rise to much litigation. The obvious remedywas to absorb the noxious gas, and to effect thismany of the larger works adopted in 1836 a methoddevised by Gossage. It was not until 1863, however,that the Alkali Act was passed, enacting that notless than 95 per cent, of the hydrochloric acid gasproduced should be absorbed, a regulation renderedmore stringent by subsequent legislation. Some ideaof the quantity concerned may be gathered from thefact that at that time about 3000 tons of the gaswere produced annually in England. To harkback to the earlier days when the makers first laidout capital to provide means for the absorptionof the gas, they naturally wondered what returnthey could get for it. This was forthcoming in theincreased demand for chlorine to • make bleachingpowder to be used for bleaching raw cotton andmaterials for paper making. Chlorine, set free fromthe hydrochloric acid by the action of manganesedioxide, was led over slaked lime, and the productwas bleaching powder. The same gas passed intocold solutions of caustic soda and potash formeduseful bleaching solutions, while if boiling potash wasused the product was chlorate of potash, a valuablesubstance in pyrotechny, in the manufacture of


certain explosives, and in medicine. The manganesedioxide employed to liberate the chlorine wasconverted into a useless product, which was a lossto the manufacturer. Science again came to hisaid in the discovery of Weldon, that the action oflime and air on the manganese waste resulted inthe regeneration of an oxygenated body which mightbe used in exactly the same way as the originaldioxide. Thus, by this process the dioxide actsmerely as an agent in liberating the chlorine, andcan be used over and over again, atmospheric oxygenbeing the real factor concerned in the change.

The Deacon process for the manufacture of chlorinefrom hydrochloric acid is a scientific method, wherebyhydrochloric acid gas and air are passed over hotbrick-work impregnated with copper salts. Theproducts are chlorine gas and water, the coppersalts acting merely as carriers of oxygen. The onlylosses are that of the hydrogen of the hydrochloricacid and the oxygen of the air.

The two processes last considered, together withthe lead chamber sulphuric acid process, being amongthe earliest of this type to be employed, serve toshow how the chemist is teaching the manufacturerto use catalytic land contact agents to effect certainchemical changes—more especially those involvingoxidation. Such processes are numerous and success-ful at the present day, effecting wonderful economies,needing only simple and compact plant, and bringingabout the required changes in the cleanest and leastwasteful manner.

The Ammonia-Soda or Solvay Process.—In thisprocess sodium bicarbonate is produced by the actionof carbon dioxide on an ammoniacal solution ofcommon salt. The bicarbonate crystallises out,leaving ammonium chloride in solution, the ammoniabeing recovered by heating the solution with lime,and used over again. The lime employed is burnt atthe works, the lime-kiln gas being the source of someof the carbon dioxide, while the gas expelled fromthe bicarbonate by calcination to make normalcarbonate provides the remainder. The salt solution


used—brine pumped up from brine pits—is subjectedto preliminary purification. Magnesium salts areprecipitated by the addition of lime, the lime saltsbeing afterwards removed by adding the necessaryquantity of sodium carbonate or ammonia liquorcontaining ammonium carbonate. After settling thesolution is drawn off and is then ready for use.

This process, which was patented by Dyer andHemming in 1838, though simple from the chemists'point of view, presented considerable mechanicaldifficulties. The first attempt to utilise t he reactionon the large scale was made by Schloessing andHolland in 1855, at a works near Paris. A t the endof two years, however, the difficulties remainedunsolved and the project was abandoned. In 1863,Solvay, who had taken out a patent two years earlier,erected an experimental factory near Brussels ; as theresult of perseverance, he secured the success of theprocess, and in 1872 established a far larger worksnear Nancy. Two years later the process was intro-duced into this country, under the Solvay patents, byMond, continued by Brunner, Mond and Co., Limited,at Northwich, where for the first time natural brinewas employed and other improvements were adopted.In 1895 the production by the Solvay process exceededthat by the Leblanc process, over which it has severalincontestable advantages. The use of brine from thepits effected a great economy that could, not beshared by the older process. The Solvay process iscleaner and the product purer. There is, of course,no sulphur to be recovered, but the chlorine from thesalt is frequently wasted as calcium chloride. As animprovement in the process, magnesia is now used insome cases to liberate the ammonia from t h e motherliquor, the resulting magnesium chloride beingsubsequently decomposed by heat into magnesia (tobe used over again) and hydrochloric acid.

Before leaving the subject of alkali we must notethat electrolytic methods of manufacture form an.increasingly important branch of the industry.Solutions of common salt are electrolysed in a specialvessel, of which the Castner rocking cell is a type,

TO CHEMICAL | SCIENCE 33

and caustic soda and chlorine, both marketableproducts, are obtained in separate compartments.When the process is modified so that the chlorineis allowed to come into contact with the soda solution,chlorate or hypochlorite may be produced byemploying hot or cold solutions respectively. Thevalue of chlorates has already been indicated;sodium hypochlorite is used as a bleaching agent andas an ingrodient in one stop of the manufactureof indigo.

34 WHAT INDUSTBY OWES

CHAPTER III.

COAL AND COAL GAS.

WE live in an age of coal and iron. The great waris waged very much with coal—or rather, what weget from it—and iron ; on the manipulation of thesesubstances by engineers and chemists the produc-tion of munitions of war largely depends. Some ofthe coal we use to smelt the iron ore and to fashionthe metal into convenient form for our use. Whenwe have won the iron we can use it, scrap it, and useit again many times, but the coal once used isdestroyed for all time. The world's annual productionof this valuable mineral probably exceeds 1,335,000,000short tons, and it is utilised (1) as a domestic fuel,with which we are all familiar; (2) as a source ofmechanical and electrical power through the agencyof steam ; (3) as a reducing agent in certain chemicaland metallurgical operations ; (4) for the productionof coke in ovens ; (5) as a source of gas for illumi-nating and heating purposes and of many othervaluable products.

The influence of scientific thought on the second ofthese uses is well known, though perhaps its extentis not always clearly recognised. For more thanhalf-a-century, steam engines were designed to meetthe requirements of coal as a fuel. It was tho bed-rock of the art of engineering. The abundance ofcoal gave impetus to invention and the modem steamengine is the result of the co-operation of physicists,chemists and mathematicians, with the practical engi-neer. As a reducing agent in applied chemistry andmetallurgy coal itself is less used than coke. Theironmaster is a great consumer of coke-oven coke asa reducing agent, and it has found an important usein the manufacture of water gas and producer gas.


The first, a mixture rich in hydrogen and carbonmonoxide, is obtained by passing steam through redhot coke ; the second, a mixture of carbon monoxideand atmospheric nitrogen is formed by the similartreatment of carbon dioxide produced by the com-bustion of coke. Although water gas has a muchgreater calorific power than producer gas, it is noteconomical to make it alone, because the reactionbetween the coke and the steam is endothermic andthe coke chamber must be heated externally to main-tain the requisite temperature. Dowson gas andMond gas are mixtures intermediate between watergas and producer gas, made by combining the twoprocesses and passing a mixture of steam and air overthe red hot coke. When the coke cools during theoperation the temperature is raised again by cuttingoff the steam and allowing air alone to pass through.The use of these gases for heating purposes is veryeconomical and finds extensive application.

As one of the most striking examples of the influenceof science in industry, coal gas manufacture demandsconsideration in somewhat fuller detail, treating ofthe distillation of a highly complex body from whichthe chemist has obtained a vast variety of usefulsubstances. The history is interesting also as anillustration of a development of philosophical experi-ment. In the seventeenth century the pursuit ofscience was the hobby of many men of learning andparticularly of the clergy. The Rev. Dr. Clayton,rector of Crofton, distilled gas from coal and collectedit in a bladder ; the fact being communicated, in1688, to the Royal Society by Boyle. In 1750, Dr.Watson, Bishop of Llandaff, not only distilled gasbut conveyed it in pipes from one place to another.The credit, however, is given to an engineer, WilliamMurdock, for the first suggestion that coal gas shouldbe generally employed for lighting purposes. In1792 he conveyed it from iron retorts through tinnediron and copper pipes, tapped at intervals, a distanceof 70ft., lighting his house and offices. His earlyexperiments were carried out at Redruth, apid sixyears later he lighted the Soho foundry of Boulton and


Watt, at Birmingham. In 1799, Le Bon commencedsimilar experiments in France. In 1807, after oneside of Pall Mall had been lighted by Winsor, a Billwas promoted in Parliament to authorise a companyfor the supply of gas in London ; in 1810 an Act waspassed for this purpose, and two years later a charter ofincorporation was granted to the Gas Light and CokeCompany, still by far the largest gas undertaking inthe world. Westminster Bridge and the Houses ofParliament were lighted in 1813, and from that timethe practice of gas lighting spread rapidly in allcivilised countries.

The gas industry is essentially chemical, though itwas formerly entirely controlled by engineers. Therewas a time when gas engineers were disinclined toshow much appreciation of the chemical aspects ofthe industry. In some works the chemists, if anywere employed, were exclusively relegated to thelaboratory for routine testing without any opportunityof acquiring experience in large scale operations* Theremuneration and prospects of such chemists were sopoor that few worthy of the name could be inducedto remain long in such employment. In manyimportant works, however, chemists acquired theessential knowledge of the engineering side of theindustry, led the way in the introduction of improvedmethods and effected developments of a far-reachingcharacter, especially in the profitable utilisation ofmaterial hitherto regarded as waste and the manu-facture of new products.

Enormous quantities of coal are subjected todestructive distillation to obtain its numerous andvaluable decomposition products, of which gas, tar,ammonia and its salts, coke, and gas carbon are madeon a huge scale and all consumed. The gas provideslight and heat, whilst the tar, useful in many ways inthe crude state, gives, when distilled, benzene, toluene,solvent naphtha, carbolic acids, naphathalene, anthra-cene, and many other substances, which in their turnyield, in the hands of the technologist, a host of ftirtheruseful bodies, including explosives, dyes, disinfectants,and drugs. Pitch, the residue of tar distillation,, is


used largely in the manufacture of patent fuel andprovides excellent material in road making. Ammo-nia is employed in medicine, in the laboratory, and incleaning cloth, and thero are many uses for its salts,especially tho sulphate, a valuable fertiliser. Gascarbon, a hard, compact substance, is used by electricalengineers in tho operation of arc lamps and fur-naces, and as a fuel in making producer gas.

The purified coal-gas of commerce roughly consistsof—hydrogen about 50 per cent, by volume, andmarsh gas or earburetted hydrogen about 35 per cent.,carbon monoxide 5 per cent., heavy hydrocarbons5 per cent., and nitrogor* 5 per cent. As it issuesfrom the hydraulic mains, which receive the vapourfrom the ascension pipes from the retorts, it is notat once ready for delivery to the consumer. Besidesits essential constituents, it contains substancessuch as condensable hydrocarbons, ammonia, carbondioxide, carbon bisulphide, sulphuretted hydrogen,cyanogen, and cyanides, some of which are of sufficientvalue to pay for their extraction, all being undesirableimpurities on account of their reducing the heatingpower of the gas or of the objectionable characterof the products of their combustion. These bodiesare therefore removed by condensation by cooling," scrubbing " with water, and by passing the 'gasover suitable materials. The operation of scrubbingwith water or with aqueous liquors from the hydraulicmains removes tho ammonia and part of the carbondioxide. The gas then passes into a chambercontaining moist ^slaked limo, where cyanogen com-pounds and the remainder of the carbon dioxideare removed, tho former in a state from which theycannot be recovered. Thoir recovery from the gas,however, can be offectocl, when desired, by a pre-liminary treatment with oxide of iron before thegas passes through tho lime chambers.

After the limo treatment the gas is led over moistoxide of iron, or Weldon mud, for absorption ofthe sulphuretted hydrogen, the material whenspent being revivified by action of the air. Thegas next passes over sulphidod lime—tho substance

i> 2


formed by the action of sulphuretted hydrogen onslaked lime—to eliminate carbon bisulphide, and,finally, undergoes an extra check treatment withoxide of iron, or Weldon mud, to remove any tracesof sulphuretted hydrogen taken up from the sulphidedlime. Subject to passing the prescribed tests forilluminating and heating power, the gas now passesto the holder—in ordinary parlance the gasometer—and is ready for the public supply.

It is obvious that science is responsible for sucha process of purification. There is scope for chemistry,physics, and mechanics in every step.

We have stated that the pipes from the retortsconvey the vapour to the hydraulic main, where itis partially condensed, and the liquid thus condensingforms two layers, coal tar and aqueous liquor. Thelatter is uppermost, and contains ammonia and othersoluble bodies. The tar was for long the bugbearof gas manufacture, its disposal being a difficultproblem, but now it is of such value that the industryof tar distillation has grown to be of great importance.It is distilled in large iron stills, the vapours evolvedfrom which are condensed, the distillate beingseparated into fractions as follows :—First runningsup to 105 deg. Cent.; light oil from 105 to 210 deg.Cent.; carbolic oil from 210 to 240 deg. Cent.; creosoteoil from 240 to 270 deg. Cent.; anthracene oil from270 up to the pitching point, this last temperaturebeing determined by the quality of pitch desired.The first runnings form two layers in the receiver,consisting of ammoniacal liquor and crude naphtha.These are separated, the former being added to thebulk of ammoniacal liquor, the latter being reservedfor subsequent treatment. The second or light oilfraction, consisting mainly of hydrocarbons of thebenzene series, is first re-distilled, yielding firstrunnings, which are added to the crude naphthafrom the original tar first runnings, and last runningswhich are worked up with the carbolic oil.

The crude naphtha is washed with caustic sodasolution to remove phenols in an easily recoverablefoim; then with strong sulphuric acid, which dis-


solves bases and unsaturated bodies, and carbonisesother impurities, forming substances of a heavy,tarry nature, and finally another soda washing isgiven to remove the residual sulphuric acid. Thespent sulphuric acid is used in the ammonia plantfor the production of sulphate of ammonia. Thenaphtha so far purified is next redistilled from aniron still. Two fractions are collected—crude benzolup to 140 deg. Cent., and solvent naphtha from 140to 170 deg. Cent., tho residue in the still being reservedfor addition to the carbolic oil. From the crudebenzol are obtained by further acid and alkali washingand careful fractionation, forerunnings of" benzol,containing benzene, toluene, carbon bisulphide andthiophenes* commercial and pure benzol and toluoLand solvent naphtha. Benzols and toluols are usedby the dye manufacturers, and at the present day inenormous quantities in the manufacture of explosives,benzene being the starting point in one processfor making picric acid, toluene being the materialfrom which T.N.T. is made. Solvent naphtha isused as a solvent for india-rubber, the higher boilingportions containing naphthalene, forming a fuel fornaphtha lamps.

The carbolic oil is treated by cooling to separatenaphthalene, and subsequently washing with asolution of caustic soda, which dissolves the carbolicand cresylic acids. These acids are recovered byneutralising the solution with sulphuric acid, whencrude carbolic acid and sodium sulphate are formed,the former being subsequently worked up for purecarbolic acid and cresylic acid, both used in themanufacture of dyes, disinfectants, and explosives.A modification of the above method is that known asthe West-Knight and Gall process, whereby theoil is treated with a mixture of sodium sulphatesolution and lime for the production of sodium" carbolate" and sulphate of lime. The solutionis worked up as before, the sodium sulphate beingutilised again for mixing with more lime. Theinsoluble oil is either mixed with the light oil or isworked up for naphthalene.


Creosot© oil is of value as a source of naphthalene,and for preserving wood from the action of - theweather and destructive insects. Naphthalene, oncea waste product, is now used largely in the manufac-ture of dyes, being the parent substance of artificialindigo, as an insecticide, and in other minor roles.Anthracene oil is the source of anthracene, a condensedhydrocarbon of the benzene series, from which thealizarin dyes are made.


CHAPTER IV.

DYES, EXPLOSIVES AND CELLULOSE.

THE invention of dyeing has been attributed to thePhoenicians, probably because it is chronicled thatSolomon sent to Hiram of Tyre for " a man cunningto work " inter alia " in purple and crimson and blue."The Tyrian purple was derived from the throats of aspecies of murex, a molluscous animal, a single dropfrom each. Other dyes from .animal substancesinclude sepia derived from the black secretion of thecuttlefish, and cochineal which consists of dried femalecochineal insects, discovered by the Spaniards in1518.

The importance of the dye industry is not so muchin the value of the dyes as in the vast interests of thetextile industry with which it is so intimatelyassociated. At a high estimate this country does notuse annually dyes to the value of £2,000,000, or, say,less than Is. per head, presuming the use to beconfined to the British Isles ; but the various industriesaffected exceed in annual value a sum of £200,000,000,and the labour involved in dyeing and printingprocesses is not far short of 2,000,000. Clearly thenwe cannot afford to be dependent on other countriesfor supplies of materials of this kind so long as we havethe power to produce them ourselves. It is wellknown that the Government has now given active sup-port to the industry ; and we may rej oice that BritishDyes, Limited, and other British dye concerns aremaking good progress towards its firmer establishment.Even before the outbreak of war, progress had beenmade in certain directions towards successful com-petition with the Germans, and since the war, by theaid of science, discoveries have been made which, inthe view of the enemy producers, were calculated to


defy our chemists for at least ten years. Comparedwith the period occupied by the Germans in dis-covering artificial indigo—about thirty-five years andan expenditure of over £1,000,000—the taunt may betaken as a compliment; but in two years from thediscovery of artificial indigo 426,100 out of 755,900acres of plantations went out of cultivation. It wasfirst sold in 1897 and in the course of a few years drovothe natural dyestuff out of the markets of the world,being only about one-third of the price, and the busi-ness passed from India to Germany.

The history of the subject covering the considerationof all the dyes known would fill volumes exceeding inbulk the " Encyclopaedia Britannica." The number ofdyes revealed by science and the substances whichscience can foretell with certainty would form dyes,and the myriad derivatives of known colouringmatters, would run into many thousands, though800 to 1000 should be more than sufficient for allpractical purposes.

The artificial dyes have several advantages overnatural products. The range of shade for any colourcan be extended and graded by the employment ofsuitable materials in a manner that cannot be attainedby using the natural dyes ; the purity of artificialdyes is much greater, and the total cost of production isconsiderably less. On account of this superiority ofsynthetic dyes, the cultivation of indigo and madder,and the trade in cochineal have been almost completelyovershadowed. Both indigo and madder have beeninvestigated by scientific men, and the compositionand nature of the dyestuffs determined. Furtherresearches have led to the discovery of methods ofsynthesis of these substances, not only interestingfrom an academic point of view, but capable of holdingtheir own and beating their natural prototypes incommercial competition. The use of cochineal hasbeen largely replaced by ,the discovery and utilisationof azo-red dyes which imitate the colour very closely,such, for example, as Bieberich scarlet. The mostimportant material used in the economical manu-facture of indigo is naphthalene obtained from the


creosote oil fraction of the tar distiller by cooling,washing the crystals produced with alkali and withacid, and distilling or subliming the product. Otheringredients are chloracetic acid and sodium hypo-chlorite, the preparation of which provides one of thenumerous outlets for the elementary chlorine of thealkali manufacturer. A short sketch of the methodof Heumann will not be out of place.

Naphthalene is converted into phthalic anhydrideby heating with sulphuric acid and mercuric sulphate.The phthalic anhydride in turn is transformed intophthalimide by heating under pressure with ammonia.By the action of sodium hypochlorite on phthalimide,anthranilic acid is produced and this substance, whentreated with chloracetic acid, yields phenyl glycine-carboxylic acid, which by fusing with alkali, dissolvingthe melt in water and passing a stream of air throughthe solution, yields indigo blue. This complex series ofoperations has met with complete commercial success.

Alizarin, the dyestuff contained in madder, is madefrom anthracene, another coal tar product, by theaction of sodium bichromate and sulphuric acid toform anthraquinone ; this is transformed by the actionof sulphuric acid into anthraquinone sulphonic acid,the sodium salt of which when fused with soda anda little potassium chlorate yields a compound ofalizarin containing sodium, from which alizarin itselfis made by the action of acid.

Bieberich scarlet, one of the naphthol azo dyos,a very important group, is, like indigo, prepared fromnaphthalene as starting material.

These three examples serve to show how thelaboratory and the factory have replaced the cultiva-tion field. There are also' thousands of new dyesprepared from benzene, toluene, and carbolic acid, aswell as many others from naphthalene. The name" coal tar dyes," however, is rather misleading to theuninitiated, for it seems to imply that the dyes exist assuch in the tar and only need extraction. What ismeant, is that the raw materials are found in the tarand need to bo transformed before anything of thenature of a dye can be produced.

U WHAT INDUSTRY OWES

The recovery and utilisation of these tar productsin the manner indicated is a great achievement. Thefirst known coal tar colour mauveine was made fromaniline by Perkin in 1856, aniline having beendiscovered by Unverdorben, thirty years earlier, bydistilling indigo.

Dyeing.—The processes of dyeing and calicoprinting are definitely chemical and depend entirelyon scientific control. Dyes are transparent and theeffects they produce vary according to tho lightreflected by the fibres of materials before they arodyed. Obviously, therefore, black cannot bo dyed,and such colours as red, blue, and yellow can onlybe dyed in the same hues, unless the material, as ispossible in the case of velvets and velveteens, bopreviously bleached. White reflects all rays andis essential as the basis for bright dyes. There mustbe chemical combination between the colouringmatter and the cloth, and the dye must bo dissolvedin a solution having a weaker affinity for the colourthan the cloth, while for economical working theremust be accurate adjustment between these relations.Wool has a stronger affinity for dyes than silk, cotton,or linen. The solutions used must be varied asoccasion requires. The choice of dyes for a givenmaterial involves the consideration of fastness towashing, and the action of light. Certain dyes willfbz themselves directly to certain fibres but not toothers without the use of mordants. The mordantscommonly employed, such as tannin, and the oxidos ofiron and aluminium, were discovered empirically,but science has explained their action, while researchhas contributed to the discovery of many new landsof colouring matter. In the art of dyeing tho nogloctof science is mainly responsible for the loss incurredby spoiled and impoverished material.

EXPLOSIVES.From a brief review of one of the most interesting

arts of peace we will pass to one of the principalindustries of war. The methods of production ofexplosives are so closely allied to those of tho coal

TO (UrTCMrOAL KOIKNOtt 45

tar dyoa that, without much modification, of plantthe dyo maker can turn his attention to tho warindustry. Wo will not go HO far a* to Ruggnst thattho development of tho dyo industry <>f tho (Germanswas part of their plan of preparations for war,but they have undoubtedly boon ahln (,<> takeadvantage of tho existence of (heir groat, factoriesfor fino chemicals and dyes in this connection. F<Yomtho discovery of pulflft fulmindnx by Ivoj nr Hacouin. tho thirteenth century, tho invoni ion of j^unpnwderand guns by Swart/;, tho monk of (<ologno, in thofourtoonth, and ilio (insl. us( of cannon in ships intho Hixtoonth (jontury, th<n*< wns littlo dt vc lopiuoabin tho H«ion<*.o or indu.stry of oxplonivos until the*ninotcMnith contnry; thon> of <u>urso, Uu> IKMHI for< xploKiv<w in mijiing and on iu<MM*ing wns far in OXOOHHof that for war. Our prosout l)UMin< rt in not tomoraliwo, but to indic-at.o with caution what sc.ioncohas dono for an industry, tlio foundation of whichlies in tho roalisation, by sciontUio nu^n, of tho cau.s<uof explosion. An oxplosivo compound or mixturois onn that can bo converted <ixo(.b(n'mica,lly und withgroat rapidity into gasooun products which at thohigh tomporuturo att.aiiuul would occupy nt ordinaryprosauro a much greater spac.o tluiu that occupiedby tho original compound or mix(.ure. The <inormouMpressure g( norat( d by Muddt n expan.sion constitutestho oxplo.sivo force, and tho principle involved buslod to tho utilisation of tho oxplo.sivo nature of unumber of substances possessing this pro[xu*ty whichmight otherwise have be<ui ov<>rlooked. Kor iunta.tu^e,it is not at all on.sy to bring about tho explosion oftrinitrotoluene, or T.N.T. It is a relatively stablesubstance ; but 11 study of its nature and comparisonwith picric acid, a similarly constituted body ofknown explosive properties, would load one toHiipposethat it could be detonated by percussion.

In J 832, Hn icon not demonstrated tho formationof an explosive substance by tho action of nitricacid on wood fibre, and in 18-15 Sohonboin obtainedgun-cotton by tr<mating cotton with a mixture ofsulphuric and nitric acids. !t« manufacture, howovnr,


though started in several foreign countries, was notsuccessful, the production being unstable anddangerous, owing to lack of care in-..the details ofthe operations involved. Sir Frederick Abel showednot only that must the starting material, cottonwaste, be carefully selected, but that thorough waterwashing after nitration was an important factor.The instability of the Schonbein material was dueto the presence of free acids. The introduction ofcentrifugal driers and of paper pulping machines forbreaking up the cotton fibre facilitated the wash-ing process, and reduced the risk of manufac-ture.

Gun-cotton is used for a variety of militarypurposes, such as filling subterranean and submarinemines and torpedoes, and it possesses the greatadvantage that it can be exploded when wet, althoughthe wet substance is safe for handling, transportation,and storage. When dry, it is exploded by a primerof fulminate of mercury; when wet, a primer ofdry gun-cotton is used. The explosive power ofgun-cotton led to attempts being made to use it asa propellant, but gun-cotton, as such, is not suitablefor the purpose because its explosion is very rapid,violent, and uncertain. Attempts to "tame " it bygelatinisation with certain organic liquids met withsuccess in the smokeless powders of Walter F. Reidand Vieille. The most remarkable result in thisdirection, however, was acliieved by Alfred Nobel,who produced a homogeneous mixture of gun-cottonand nitroglycerine by the evaporation of a solutionof those substances in acetone. By the moderndevelopment of this method, gun-cotton, nitro-glycerine, and a small quantity of mineral jelly aremixed well with acetone, and the resulting pasteis squeezed through, jets to form continuous cords,which, when dry, have the appearance of catgut.This is cordite, the propellant explosive used infirearms of many sorts and sizes.

Nitroglycerine, mentioned above, was discoveredby Sobrero, in 1847, but its explosive propertieswere not utilised until its value was recognised by


Nobel. It is a fairly heavy oily liquid, detonatingviolently by percussion, when struck a sharp blow,or suddenly heated. On account of these propensitiesthe substance, as such, is seldom, if ever, employedat the present time, but is converted into a saferform by incorporation with some inert material, as,for example, magnesia alba, or kieselghur, theproduct in the latter case being dynamite. In thisform, although a certain amount of danger.stillattends its use, it is much safer than in the free state.Sometimes nitroglycerine is incorporated with anexplosive diluent, as with collodion cotton, toproduce blasting gelatine, a body with explosivepower exceeding that of nitroglycerine; while amixture of thinly gelatinised nitroglycerine with nitre,woodmeal, and a trace of soda, gives us gelatinedynamite, another useful blasting agent. Explosivesof this class, used largely in mining, quarrying, andcivil engineering operations, have been speciallydeveloped by Nobel's Explosives Company.

When we come to consider the class of substancesused for the bursting charge of shells, it is difficultto give any individual the credit for their first applica-tion, or, shall we say, " give the devil his due."Picric acid, the oldest of these, was discovered in1799 by Welter, and its nature as a derivative ofphenol was elucidated by Laurent in 1842. Preparationsof picric acid are used by various countries, as a militaryhigh explosive under such names as lyddite, shimose,and melinite. Its great disadvantage is that it formsvery sensitive and highly explosive salts when leftin contact with metals for any length of time. Thisdrawback is not shared by T.N.T., which has come somuch into use during the war. The substitutionof T.N.T. involves a loss of explosive power, but thisis more than counterbalanced by the advantagesgained. It is used both alone and in conjunctionwith other substances such as aluminium powder andammonium nitrate. Such a mixture is ammonal,a safe but very powerful explosive employed by theAustrians. Another very violent explosive is tetra-nitroaniline, discovered by Fleurscheim. It is not


very largely used, as the materials required for itsmanufacture are comparatively expensive.

The whole industry is based on science, and shouldbe controlled by trained men of science in everydepartment. It has demanded its toll of human life,in spite of extraordinary precautions ; but withoutscience that toll would have been far greater, andcertain it is that without the search for knowledge,the desire to experiment, and the power to applythe knowledge gained, such an industry could notexist.

CELLULOSE.

Cellulose.—Cellulose belongs to the class of sub-stances known chemically as carbohydrates. Allcarbohydrates consist of carbon, hydrogen, andoxygen, the second and last occurring in the sameproportions as in water.

Cellulose is not affected by ordinary solvents, butis attacked by strong sulphuric acid, yielding astarch-like body called amyloid, and is dissolved byammoniacal solutions of copper salts, from whichit can be precipitated in an amorphous form by theaddition of acids. This property constitutes the basisof one method of making artificial silk.' It may bementioned, incidentally, that when heated to 200-220 deg. Cent, with caustic potash, cellulose is brokendown into oxalic acid, and large quantities of thatacid are made in this way. Sawdust is fused withpotash in iron pans ; the melt when cold is extractedwith water, and the oxalic acid is precipitated as theinsoluble calcium salt from which it is subsequentlyliberated by the action of sulphuric acid. Thisprocess, which was discovered by Gay-Lussac in 1829,and was first employed on the manufacturing scaleby Dale in 1856, is far cheaper than the older methodof oxidising sugar or starch with nitric acid. ~~

The cellulosa industry is held to include the manu-facture of cotton, linen, paper and pasteboard, andhemp and jute articles. We do not claim much inthe way of debts to science in connection with the


manufacture of cotton and linen, but will choosepaper and pasteboard for our purpose, and then referbriefly to artificial silk and celluloid.

Paper may be regarded as one of the civili-sing agents in the existence of man. It is diffi-cult to imagine what progress the world wouldhave made without it. The early history of paperis obscured by conflicting records. It is believedto have been used in China long before the Greeksand Romans ceased to use papyrus, but accordingto M. Terentius Varro, a voluminous writer contem-porary with Cicero, the invention was devised atAlexandria on the conquest of Egypt by Alexanderthe Great (B.C. 331). It was in use in Arabia over1000 years ago, and the Crusaders are said to havebrought the industry to Europe. The earliest MS.on cotton paper in the Bodleian Collection in theBritish Museum is dated 1049, while one on the samematerial in the Library of Paris is dated 1050. Papermade of linen rags was in use here in 1170. TheMoors are credited with having introduced theindustry into Spain, where 12th century specimensstill exist. The first paper mill in this country wasestablished by Tate, in Hertfordshire, in the reignof Henry VII., who visited it, and the first importantone was started at Dartford, in Kent, in 1588, orthereabouts, when Queen Elizabeth granted amonopoly, for gathering rags and making paper,to Spielmann, tho Court Jeweller.

Until the end of the 18th century paper was madeby tearing and beating rags to pulp in a machine,dipping a wire sieve into the pulp, transferring themass to a felt and pressing it in moulds of varioussizes. About 1800 a Frenchman devised a methodof making it in a continuous web, which he introducedinto England, where it was steadily improved untilabout 1860, by which time, for all ordinary purposes,it had superseded the old hand-ma^le method,although the latter is still ernpldyed for bank notes,bonds, ledgers, and important documents.

With the introduction of machine-made papers


the output has been vastly increased, the cost reduced,and the variety extended to such a degree that thereare now probably more than 20,000 lands. In 1820the machines produced paper at the rate of about40ft. per minute ; the most modern can now exceed500ft. per minute. Before 1860, paper consistedalmost entirely of rags, but about that time anEnglishman introduced the use of esparto, Macrochloa(orlStipa) tenacissima, a grass also employed for makingmats, nets, baskets, &c, of which the consumption inpaper-making is normally about 200,000 tons a year,at £4 to £4 ICs. per ton, almost all of it coming to thiscountry for the production of fine printing papers.Over 400 different materials have been tried in theindustry, but rags and esparto are the chief for goodpapers. Since the year 1880, chemical wood pulphas been used as the chief material for middlingkinds, and more recently mechanical wood—made bycrushing wood between rollers or by pressing' itagainst a grindstone—mixed with varying quantitiesof chemical wood pulp, has been employed for thecheapest newspapers and common printings.

Science has played an important part in thedevelopment of the paper industry. The introductionof cheap bleaching agents such as chloride of limeto which, as a by-product of the Leblanc processwe have already referred, has effected considerableimprovements and economies, while the utilisation ofesparto and wood has been made practicable onlyby scientific research, the processes evolved from whichwe will now outline.

Wood fibre is a lignocellulose, a compound ofcellulose and a complex substance called lignone,which acts apparently as a binding material. Theforest wood is deprived of its bark and cut across thegrain into small chips, which are cleaned and thenboiled at high temperature, under pressure, in asolution of caustic soda. From coniferous wood theyield of cellulose is about one-third of the weightof the prepared wood treated, the other two-thirdsbeing taken up by the alkaline solution. The causticsoda required, amounting to about 20 per cent, of


the weight of the wood, is recovered by evaporatingthe spent liquor, incinerating the residue and treatinga solution of the ash with lime. The organic matterin the residue, on burning, provides a good deal ofthe heat necessary for evaporating the solution.The process, however, has one disadvantage in thefact that a proportion of the cellulose is,, destroyedby the action of the strong alkali. In order to obtainbetter yields two modifications have been introducedcomparatively recently. One consists in the sub-stitution of sodium sulphide for the caustic soda,the sulphide being prepared on the spot by the reduc-tion of sulphate of soda with the residue obtainedby evaporating the spent alkali. The cycle ofoperations is then completed by making up theworking loss of sodium sulphide by the addition ofsulphate of soda to the residue before incineration.The other modification consists in the applicationof an acid hydrolysing agent instead of the alkali.The acid substance employed is a solution of calciumor magnesium bisulphite containing approximately4 per cent, of sulphur dioxide. This solution isprepared by passing pyrites gases up a tower filledwith calcite or dolomite down which water is trickling.The cost of the process is slightly higher, but not outof proportion to the increased yield of cellulose.

The cellulose obtained by either of the methodsis mashed to a pulp, washed free from adhering liquor,and bleached with chloride of lime and sulphuricacid, before being utilised in the manufacture ofpaper. Those who are interested in this subject maybe invited to study the series of articles on " PaperMaking," which appeared in Vol. CXX. of THEENGINEEB.

" Artificial Silk"—The production from celluloseof materials resembling silk is the result of manyyears of scientific research and costly experiment.In 1889 the Oomte de Chardonnet produced thefirst artificial silk by nitrating cellulose and dissolvingthe resulting product in a mixture of alcohol andether, thereby obtaining a viscous liquid which he-forced through holes of very small diameter into water.


The threads thus produced were then subjected tothe reducing action of ammonium sulphide and con-verted into an amorphous cellulose having theappearance of silk.

The method now extensively used is that devisedby Cross and Bevan, who have contributed largelyto the existing knowledge of the chemistry andtechnology of cellulose. The starting material,wood pulp, is treated successively with caustic sodasolution and carbon bisulphide, the viscous massthus obtained being forced through small apertures,from which are produced filaments which are spuninto a fine material also closely resembling silk.

Celluloid—a very useful substitute for horn,tortoiseshell, ivory, &c.—was first made in 1869by treating nitrocellulose with camphor and alcohol.Its inflammability, however, has proved to be avery serious drawback, attempts to overcome whichhave met with some success. By the substitutionof acetate of cellulose for cellulose itself in the process,a non-inflammable product—sicoid or cellon—isformed which for some purposes is more usefulthan celluloid.


CHAPTER V.

OILS, FATS AND WAXES.

OILS may be divided into: (a) animal, includingwhale and fish oils, stearin, which is mainly obtainedfrom beef and mutton suet, and neats-foot oil fromthe feet of cattle ; (b) vegetable, such as olive, linseod,cotton seed, maize, palm, rape, castor, and turpentine,and essential oils ; and (c) mineral oils, so-called, suchas petroleum, ozokerite, and shale. "It is difficult tomake a sharp division, however, for the reason thatsome are obtained from more than one of these sources ;for instance, stearin exists in the vegetable kingdom,and petroleum is certainly derived from the productsof long submerged fish life. The tar oils we havoalready noticed in dealing with coal and coal gas.Among the most useful substances at our disposaloils are employed as fuel, illuminants and lubricants,and provide us with material for food and medicine,as well as for the manufacture of paints and varnishes,polishes and perfumes.

Oil has been defined as a neutral fatty substance,liquid at ordinary temperatures ; but although we arenot satisfied with the definition, we will not attemptto improve upon it, preferring rather to proceed withour task of indicating th* influence of science in thevast field of industry involved. That influence hasbeen more marked in the direction of improvementand adaptation rather than of new and striking dis-covery. In some cases, however, scientific principleshave been applied to the fundamental processes ofoil production, with the result that substances at onetime ignored as valueless have become the source ofproducts now regarded as indispensable, while thescience of geology has rendered inestimable service inlocating and surveying sources of mineral oil; indeed,

R 2


a knowledge of economic geology is essential to allmining engineers: )

The world's output of petroleum before the war wasprobably not far short of 350,000,000 barrels of 42gallons, of which about two-thirds were produced inthe United States. Dame Nature seems anxious toget rid of it as if it were the offensive exudation of adeep-seated abscess. If nothing could be profitablyextracted from it we might well wish ifc to remain inthe bowels of the earth, counting it nothing but anuisance when it came to the surface. Science canat least claim to have made it useful, seeing that bythe process of fractional distillation this disagreeablenatural substance can be made to yield in enormousquantities such valuable products as illuminating gas,motor spirit, cleaning spirit, kerosene or lamp oil,paraffin wax, vaseline, and a viscid residue used asfuel. The crude petroleum itself would be useless forany of the purposes to which its derivatives areapplied, mainly -on account of its highly volatileconstituents, which are a source of danger in transportand storage, owing to the inflammable nature of thevapour arising from it. The crude oil is conveyed bypipe lines, in some cases over a distance of severalhundred miles, to the refinery,,.where it is distilled intotemperature fractions. Tl*6' lighter fractions arepurified Nby washing with sulphuric acid, alkali andwater ; while sulphur, when it occurs in objectionablequantity, must be removed by means of copper oxide.Among the higher fractions lubricating oil is purifiedby filtration through animal charcoal..

The lightest fraction, cymogene, which requiresspecial cooling and pressure for its condensation, isused in ice-making machines. Other fractionsobtained are rhigolene, the illuminaiit used in the pen-tane standard lamp, and as a local anaesthetic in surgery;gasolene, employed for the carburation of water gasfor illuminating purposes, for making cc air gas," andas a solvent; ligroin, also a solvent; benzine or petrol,which supplies us with motor spirit; and kerosene orlamp oil. Among other products may be mentionedparaffin wax, which, with an admixture of stearic

TO CHEMICAL SCIENCE

acid, is used for the manufacture of candles, solar oils,various grades of lubricants, and vaseline. Thequantity of lighter fractions can be increased ifdesired by the " cracking" of the more complexbodies.

Astatki, the residue from the distillation of Russianpetroleum, yields, on distillation, an excellent illumi-nating gas, besides quantities of benzol, toluol,naphthalene, anthracene, and pitch.

The shale oil industry, founded by James Young,of Kelly, in 1851, which produces valuable quantitiesof illuminating and lubricating oils, ammonia, andparaffin wax, depends in a similar manner on scientificoperations.

We claim less for science in the extraction ofanimal and vegetable oils, which has beenpractised since time immemorial, but must place tothe credit side of the account the responsibility for thedifferentiation and classification of such oils, theselection of their most useful applications, withmethods of purification and of analysis and valuation.

Vegetable oils, such as linseed oil—a so-calleddrying oil—and turpentine are used as vehicles in themanufacture of paints and oil varnishes. The paintindustry has derived great benefit from science in thediscovery and application of new pigments, and in theimprovement of the older methods of making pig-ments. Turpentine is the starting material for themanufacture of artificial camphor, a synthesis that isa credit to organic chemistry, and although theartificial product cannot as yet be made to competewith the natural substance, it renders good servicein keeping down the price of natural camphor, of whichthe production is practically monopolised by theJapanese. Other vegetable oils, such as"* olive oil,rape oil, maize oil, and castor oil, are employed aslubricants, whilst some are good illuminating oils.

The essential oils, of which oil of turpentine is anexample, are vegetable oils used in many cases asperfumes. There are three methods of winning theessential oils: (1) by distillation with steam; (2) bypressure of the plant substance and (3) by extraction


with suitable solvents. Science has entered largelyinto the essential oil industry by finding the con-stitution of many of the odoriferous principles, whiclihave afterwards been successfully made in the labora-tory from simple materials. In some cases, where theactual substances have not been made, very closeimitations have successfully competed with thenatural products. Examples of the first are terpinol,which is the important constituent of Lily of the Valley,and coumarin, New Mown Hay and Jockey Club ;wliilst in the second class we have such substances asionone and nitrobenzene substitutes for essence ofviolets and oil of bitter almonds respectively.

SOAP AND CANDLES.The soap and candle industries must now be

regarded as offshoots of the oil industries. Their originis remote, but it was not until 181J3, when Chevreulpublished his remarkable researches on the composi-tion of oils and fats, that anything was known of thetrue nature of the processes involved in their manu-facture. Nowadays the chemist should be in para-mount control of their production. The recovery .ofglycerine, which at one time flowed into our riversand streams as a waste product, was a scientificachievement of far-reaching importance, as we haveindicated in our remarks on explosives, while its usein medicine is considerable. Incidentally we maymention- also that glycerine, mixed with water,prevents evaporation and freezing, and this propertyfinds application in the mechanism of gas meters.

Both animal and vegetable oils are used in themanufacture of soap and candles. When fats and oils—such as tallow, palm oil, olive oil—-jure boiled in largecast iron pans with caustic alkali, they becomfc decom-posed and yield an alkaline salt of the fatty acid—soapand glycerine. The excess of alkali and the glycerineare separated by the addition of a solution of commonsalt; the soap, being insoluble in the brine, rises to thetop, and is ladled out as a granular curdy mass, runoft into'frames—boxes—to cool and solidify. Hardsoaps, such as curd and yellow soap, are compounds

TO CHEMICAL vSCIENCE 57

with soda, consisting of about 26 per cent, of water,7 per cent, of soda, and 66 per cent, of fatty acids,with, in the case of yellow soap, a small percentage"of resin. Soft soaps are compounds with potash, orpotash and soda, with fatty acids derived from dryingoils, such as whale and seal oils, linseed, &c. Withregard to the water content of hard soap it has beenrumoured that, since soaps containing as much as90 per cent, of water have been encountered, itappears to be the aim of some soap makers to causewater to stand upright.

CANDLES.

The old tallow dips, prepared by dipping a wickrepeatedly into melted tallow, gave rise, on burning,to a pungent substance called acrolein, produced bythe decomposition of the glycerine combined in thetallow. Modern candles are without this disadvan-tage, as they contain no glycerine, the free fatty acidsfrom wliich they are made being liberated from thefat either by the hydrolytic action of sulphuric acid,or.by precipitation of the lime salt and its subsequentdecomposition with sulphuric acid. The fatty acid—e.g., stearic or palmitic acid—so prepared is melted andcast round about wicks in moulds of pewter or tin, -orsometimes of glass, supported in a wooden frame, theupper part forming a trough. The wicks are arrangedtaut, the wax is poured in, cooled with water to solidi-fication, and removed as candles. All sorts of wastefats, such as those from wool washing and glue making,are used for making candles, the free acid beingextracted by treating the fat with sulphuric acid.

These industries furnish examples of the utilisationof waste products. The soap used for cleansingpurposes in yarn mills is recovered by precipitatingthe soap from waste liquids with lime, and pressingthe precipitate into briquettes, from which sufficientgas can be obtained by distillation to light the mills.Efforts are at the present time being made to recoverfat from sewage, mainly for the sake of the glycerinecontent.

5S WHAT INDUSTRY OWES

EDIBLE FATS.The invention of butter substitutes, now popularised

by prevailing conditions and the need for the exerciseof economy, is due to the chemist. These substancesare commonly made by mixing intimately a solidanimal fat, such as stearin, with some vegetable oil,such as cotton seed or cocoanut oil, and milk. Theuse of solid animal oil for this purpose absorbs someof the raw material formerly available to the soapmaker, but the deficiency has been made good by theconversion of the plentiful supply of vegetable oils,such as olive oil, into solid fats by hydrogenation inthe presence of finely divided nickel, to which wereferred in dealing with that metal.


CHAPTER VI.

LEATHER,

U P to the close of the eighteenth century theprogress of industry was slow but sure, much of itbased undoubtedly on the workings of great mindsand patient inventive genius, and much again onchance discovery; but the nineteenth centurymarked an epoch of development, definitely hastenedby the advance made simultaneously in mechanical,physical, chemical, and biological science. Yet whenwe consider all that was done in ancient times, forexample, in the winning of metals, in the dyeing offabrics, in agriculture and the domestic arts, weare forced to marvel at the vast amount of knowledgeand experience, commonly inferred to as empiricism,accumulated for centuries before the advent ofmodern science. We are also convinced that thereis no finality in the matter, and that what appearsto be ideal to-day will be improved upon to-morrowor the day after.

An ancient industry is the manufacture of leather,which had seemingly reached the highest degreeof efficiency centimes ago if one may judge by exist-ing specimens. To the modern chemist, however, thesubject is open to further investigation, involvingproblems directed to the speeding up of productionand decrease of cost without diminishing the quality—aims not easily attained, as many have learned from,personal experience. In fact, one of our leadingauthorities has recently expressed the opinion thatthe science of this important industry is but in itsinfancy. We are reassured, however, by the statementthat the work of Professor H. B. Procter and theLeather Department of the University of Leeds, waslargely the factor which rendered it possible for the


nation to supply the enormously increased demandfor the military equipment of the Allied Armies,including boots, belts, leggings, saddlery, traces,dressed sheep skins, and numerous minor require-ments, besides the driving belts of the munitionfactories. With such a demand to meet, the pricefor the time being of leather for furniture, port-manteaux, gloves, book-binding, and parchment isnaturally high.

The processes whereby raw hides are convertedinto useful and durable materials by treatment with,various solutions of substances of animal, vegetableand sometimes mineral origin, are distinctly chemicaland biological. They are investigated and explainedb}7 research, and modified and superseded by betterprocesses, so far as the increase of knowledge admits,wliile accidental impurities of a harmful nature inthe liquors employed can be traced and their presenceavoided.

The hydrochloric acid washing given to hidesthat have been unhaired by lime, to free them fromthat substance, is clearly an operation of a scientificnature, and is also the chemical investigation of thewater supply, the quality of the water being important.The science of bacteriology has. rendered invaluableassistance in furthering our knowledge of puering—the process of softening hides prior to tanning.The changes involved in the old process of treatingthe unhaired and washed hides with an infusion ofdog-dung have been investigated very thoroughly byscientific methods, and have been shown to be theresult of bacterial action. Patents, founded on thisknowledge, have been taken out for the use ofartificial cultures of bacteria instead of the obnoxiousinfusion referred to. Some of these methods giveexcellent results, and would doubtless be more gener-ally adopted were it not for the conservatism of theworkman and his dislike of the trouble necessitatedby a change of procedure.

The oldest method of treating skin and hide forthe purpose of preservation in a flexible state, whichconsisted in kneading with fatty substances, is of


historic interest only, though chamois leather isstill prepared with oil. Next in chronological ordercomes vegetable tanning, still very extensively used,the tanning liquor being an infusion of some bark,e.g., of oak or willow. Up to the end of the eighteenthcentury the prepared hides were simply soaked in astrong infusion of the tan, biit about that time Seguin,a Frenchman, introduced a method for soaking thehides successively in tan liquor, or ooze, of increasingstrength, the untanned hide going first into theweakest, the completely tanned material being takenfrom the strongest liquor. By this means thoroughpermeation by the tan liquor was ensured, and thequality of leather considerably improved. Thismethod was patented in England by William Desmondin 1795.

Sir Humphry Davy investigated the process oftanning with useful results, indicating the natureof the action between the hide and the tanningmaterial, but only recently has science obtained ahearing in the industry. The reason for this is notfar to seek; the changes involved in tanning areexceedingly complex in character, and depend to alarge extent upon the properties of substances in acolloidal condition. Examples of this state are tobe found in solutions of gelatine and starch havingproperties different from ordinary solutions, suchas that of sotting with the formation of a jelly.The scientific study of the colloidal state is now beingmore vigorously pursued, and as our knowledgeof it increases we may expect further advances inthe leather industry.

Mineral tannages, of which alum was the firstknown, aro also of interest. The " tawing " solutioncontains alum and common salt, the latter serving tocounteract the swelling of tho hide produced by thefree acid in the alum solution. Salts of the metalsiron and chromium, chemically similar to aluminium,have been used for tanning, and although iron saltshave no application as tannages at the present time,chrome tanning is a very important industry, foundedand reared upon scientific knowledge. Many patents

C2 WHAT INDUSTRY OWES

have been taken out, including those by Knapp in1858, by J. W.—later Sir J. W.—Swan,' by Hein-zerling in 1879 (the first commercially sxiccessfulprocess introduced into England) and that byAugustus Schultz, a New York dye works chemist, in1884. Valuable scientific work has also been done inthis branch by Eitner and by Procter. A soft anddurable leather can be produced which will fix an. aciddye without a mordant.

Leather cloth substitutes for leather, used forcovering furniture, for bookbinding, stationery cases,pocket books, and many other useful articles, arealso produced under scientific supervision. Thisindustry, however, with that of linoleum and similarmaterial, might have been dealt with as branches ofthe oil industry had we attempted to deal morecomprehensively with that subject.

Apart from skins and hides there are other productsof the slaughter-house, such as horn, blood, hair andbristles, waste wool and the like, from which valuablechemicals such as cyanide are produced. Glue* too,is made from the chippings of hides, horns and hoofs,which are washed in lime-water, boiled, skimmed,strained, evaporated, cooled in moulds, cut intoconvenient pieces and dried on nefcs. The processesare nowadays supervised by trained chemists.


CHAPTEB VII.

RUBBER.

RUBBER, formerly commonly called caoutchouc,was originally imported from Fronch Guiana. I twas obtained from the Siphonia elaslica, andfrom Brazil, from the Siphonia or Hevea Brazilien-sis, lutea and brevifolia, through the port of Para,and later from, the ficus elaslica, or india-rubbertree. It was first brought to Europe in the earlypart of the eighteenth century, but it was manyyears before its usefulness was realised. Priestley,the discoverer of oxygen, suggested its use for re-moving pencil marks and, in 1791, Samuel Piatobtained a patent for making waterproof fabrics bydissolving caoutchouc in spirits of turpentine.Hancock, in 1823, and Macintosh followed on similarlines, but the invention of the vulcanising process byCharles Goodyear, whereby the addition of sulphurgave it the consistency of horn, marked the startingpoint of still greater developments.

The rubber industry has recognised the importanceof scientific control, by botanists and chemists, inplanting, cultivation and tapping, with consequentincreased yields. Chemists examine the latex, andsupervise its drying and preparation for use. Thovariability of tensile strength is largely dependent onthe size of the globules in the latex, which is valuedaccordingly. No standards of purity have beenestablished, but fine Para is generally consideredsuperior to other varieties.

For nearly sixty years chemists of all countrieshave devoted much time and labour to its syntheticproduction in the laboratory. In 1860 GrevilloWilliams isolated a compound, which he calledisoprene, from the products of the distillation of

64 WHAT ESfDUSTRY OWES

natural rubber. Nineteen years later, Bouchardatshowed that a substance very closely resemblingrubber could be reproduced from isoprene by theaction of strong hydrochloric acid, and that by theaction of heat alone isoprene yielded turpentine.The work of the French chemist was confirmed, in18S4, by Professor—now Sir—William Tilden, whosuggested a formula for isoprene, which subsequentlyproved to be correct, and also obtained isoprene fromturpentine. Later, these researches formed the basison which the synthetic rubber industry was founded,though German chemists, who have also done goodwork in this field of investigation, lay claim to havingestablished principles the credit for which was clearlynot due to them. Among other British chemists whohave contributed to the investigations on the subjectmay be mentioned Professor W. H. Perkin, Dr.Strange, and Dr. F. E. Matthews. Two chemicallydifferent rubbers are produced : isoprene-caoutchoucand butadiene-caoutchouc. The raw materials,isoprene and butadiene, are obtained from a varietyOf substances, including turpentine, isopentane (fromthe" rhigolene fraction of American petroleum), coaltar (the material from this source being para-cresol,one of the homologues of carbolic acid), starch andcellulose. The raw material is converted intocaoutchouc by methods, involving (i.) polymerisation,by heating under pressure with a suitable substancesuch as acetic acid, and (ii.) polymerisation, by theaction of sodium. The latter method, discoveredalmost simultaneously by F. E. Matthews in Englandand Harries in Germany, is the more convenientand gives the greater yield, although the resultingproduct does not vulcanise so well as that from theformer method. All this is progress, As in the caseof indigo, science, if successful, will help one form ofindustry to the detriment of another; the scientificwork on the plantations tends constantly to increasedyields and economical working, and"_ the artificialrubber has not as yet displaced the natural either injts properties or in cost of production.


CHAPTER VIII.

MORTAR AND CEMENT.

THE simplest and most ancient cementitiouBmaterial is mud, which is still used, reinforced bysticks and grass, by African natives in the construc-tion of their huts. Ordinary mortar is made ofwater, lime, and sand intimately mixed together.Science has shown that there is no chemical unionbetween the lime and sand; that the sand actssimply as a diluent, preventing undue shrinkage,which occurs when lime is used alone ; that the settingis due to loss of water, and that the hardening iscaused by the gradual formation of interlacingcrystals of calcium carbonate, which effectively bindthe material into a coherent mass.

Long before these facts had been established,experience had proved that a pure or " fat " limeproduced a better mortar than an impure lime. Inthe case of hydraulic mortars and cements, however,the knowledge of their structure and action wasindefinite until 1887, when the researches of LeChatelier were published, though a fairly systematicinvestigation of the nature of hydraulic mortar orrather of the hydraulic limestones employed in itsmanufacture, was made about the year 1756 bySmeaton, whilst searching for the most suitablebinding material for the foundations of the EddystoneLighthouse, which he had been commissioned torebuild. He consulted his friend Cookworthy, achemist, who instructed him in the analysis of lime-stones, and he found that clay was an essentialconstituent of a hydraulic limestone, the poor limeobtained on burning it being far superior to fat limefor making mortar intended to withstand exposureto water.


Cements are made by heating in a furnace anintimate mixture of limestone or chalk and clay to atemperature at which clinkering takes place. Theproduct is broken up, finely ground, and put upon themarket as cement. " Roman " cement was first madeby James Parker in 1796, by heating argillaceous lime-stone containing, already mixed, the two necessaryingredients. The manufacture of Portland cementwas founded on attempts to imitate Roman cement,using a mixture of lime and clay instead of theargillaceous limestone. Nothing was understoodof the why and the wherefore of the process, andoften the best part of the product was rejected inthe unslakeable portions. Chemical action in thefurnace was unthought of, and even when it. wasevident to scientific men and duly published, con-siderable time elapsed before the manufacturerstook advantage of the efforts of science towards thefurtherance of their industry. It is now knownthat chemical action between the lime and the clayin the furnace effects the formation of silicate andaluminate of calcium. When the cement is treatedwith water, these, compounds are decomposed withthe production of slaked lime, and the acids derivedfrom silica and alumina. These substances againinteract, with the formation of the hydrated silicatesand aluminates as interlacing crystals, giving tenacityto the preparation, with the result that first settingand subsequently hardening take place, thesephenomena being merely stages in one process.Thus the researches of chemists have establishedfacts which have been most serviceable to the cementmaker in increasing the efficiency of his productthrough the choice and treatment of the bestmaterials.

We owe more than this, however, to the studyof the chemistry of cement. It remained for chemiststo show the dangerous effect of certain impurities,such as magnesia, in excess, and sulphates, on theresistance of cement to the attack of water. Suchsubstances must be carefully excluded within well-defined limits. When cement is used to make


concrete foundations exposed to sea water, the massmust be either very compact and impervious, orbe covered with an impenetrable stone facing, forthe reason that sea water contains sulphates andsalts of magnesium in plenty, and, consequently,if penetration by the water takes place, the cementdecomposes and the life of the structure is corres-pondingly shortened.

It is obvious that for such a substance, on whichthe stability of costly buildings and structures solargely depends, the provision of a definite standardspecification became a necessity. The BritishStandard Specification was formulated in 1904 by asub-committee, appointed by the EngineeringStandards Committee, including engineers and con-tractors, chemists, architects, manufacturers, andrepresentatives of official bodies using large quan-tities of Portland cement for public works. The.specification provided for both chemical and mechani-cal tests, and, although subsequently modified inthe direction of improving the quality of the cementsupplied under the specification, remains essentiallythe same to-day—a definitely scientific safeguardaccepted alike by producers and users.

We have indicated how the explanation of scientificphenomena tends to improvement in manufacture,and it is interesting to note that a reason has beenadvanced for the use of straw in the making of bricksby the Israelites. It is not a suitable binding material,but Acheson has shown that clay is rendered moreplastic by the addition of tannin, and that an extractobtained by soaking straw in water produces thesame effect. The Israelites complained, therefore,of the hardship of working with less suitable materials,while they had to produce the same tale of bricks.Possibly the use of grass assists in the same way theAfrican natives in making their mud huts.


CHAPTER IX.

REFRACTORY MATERIALS.

A MATERIAL is termed refractory when it resiststhe ordinary treatment to which materials of itsclass are subjected ; it may be a mineral which doesnot yield readily to the hammer, or an ore not easilyreduced. In recent times, however, the term hasbecome specially associated with substances that willresist economically the temperature of a furnace, andthe corrosive action of other substances with whichthey come into contact. Refractoriness may, there-fore, be a vice or a virtue, according to circumstances,and a given material may be refractory in one process,but break down easily if employed in another.

The increased demand for refractory materials duringthe war, particularly in the manufacture of steel andglass, has shown the need for further scientific investi-gation. Experiment on the large scale is costly,especially if carried out in an unscientific manner.The help of chemists is therefore essential in deter-mining the composition and the chemical and physicalproperties of such substances, having in view thepurposes to which they are to be applied. Thework is not confined to the investigation of knownrefractories, but is extended to the discovery andutilisation of new refractories to cope with the con-ditions created by their employment in high tempera-ture furnaces.

Having selected a suitable material, from thechemical point of view, it is necessary to ascertainwhether it will withstand, without shrinkage, fusionor softening—and consequent deformation—thetemperature required for the desired reaction. Therefractory that will last for ever has yet to be found,but that with the longest life is the most economical,


provided the saving effected by the increased lengthof life—ronowals boing loss frequently roquired—plus the saving of time and labour, in more continuousrunning of the furnace, is proportionate to anyadditional coat. Tho subject has long boon treatedmore or Ions scientifically, the older refractoriesbeing classified into acid, basic, and neutral materials.As examples of tho acid class wo havo fire-clays, suchas ganistor, tho highly siliceous .material used forlining acid Bessornor converters ; hi the basic class,such substances as lime, magnesia, and calcineddolomite ; while among the neutral refractories womay include gas carbon and graphite. These mate-rials havo proved eminently suitable for some pur-poses, but with the uso of tho electric furnace werequire substances still more rofractory, and in recentyears science has provided a number of thorn.

Carborundum, tho extremely hard and refractorycarbide of silicon, was first made in 1801 by Achoson,who obtained it by heating grnphito with sand in theelectric furnace, and it; is now employod as a rofractorylining for such furnaces, besides boing useful as anabrasive. It has also boon incorporated with cementto give grip to surfaces, as on staircases subjected toconsiderable wear. Other modern refractories arealundum—fused aluminium oxide—silicon, fusedsilica, zirconia, arid artificially made graphite. Cru-cibles of graphite, intimately mixed with sufficientclay to give the mixture coherence, are far preferablefor many purposes, and much more durable than thosemade of clay alono.

WHAT INDUSTRY OWES

CHAPTER X.

GLASS AND ENAMELS.

THE manufacture of glass dates from the firstperiod of Egyptian history. Egypt, the instructorof the world in so many arts, possessed in very earlytimes craftsmen skilled in making, blowing, colour-ing and cutting this most remarkable and usefulmaterial. The industry survived through the vicis-situdes of the country until the time of Tiberius(A.D. 14-41), who brought Egyptian glass workers toRome, where the art flourished until the decline of theempire, during which the principal centre of manu-facture was transferred to Byzantium. The valueattached to glass by the ancients is indicated by thecircumstance that the industry was always supportedand encouraged by the most powerful and influentialrulers, migrating with their power from one countryto another. However, at the time of the fall ofConstantinople it had become established in variouscentres, of which the chief was Venice, where it soonattained such proportions as to give occupation toover 8000 persons.

In the Middle Ages the industry was developed inGermany and Bohemia, especially in the latter country,which, owing to the native supply of pure quartz,ultimately superseded Venice as the source of the finestglass. Inl870 glass making gave employment to 30,000workers in Bohemia. The invention of glass mirrorshas been attributed to the Germans, the originalmethod being to back the glass with polished metal.Glass was first used for windows in England aboutthe end of the eleventh century, and was made herein- the fifteenth, but with little success until about1557, when French artisans were employed in London.In 1670 Venetian workers were brought over to make


the heavier and finer kinds, and in 1771 the industrybecame more firmly established by the formation ofthe British Plate Glass Company, whose successorsare still in existence at St. Helens.

The scientific study of glass was first made on thephysical side, its transparency, permanence, and theabsence of crystalline structure with consequentbirefringence, combining to render it an almost idealmaterial for the construction of the essential parts ofoptical instruments. In fact, the science of optics,with its manifold applications to spectacles, micro-scopes, telescopes and spectroscopes, owes its exist-ence to our possession of glass. The first investiga-tions in the chemistry of the subject were made witha view to the improvement and better adaptation ofglass to optical purposes. Up to 1829 the onlyvarieties of optical glass were soda-lime or crownglass, potash-lime or Bohemian glass, and potash-leador flint glass, also known as crystal or strass* thesebeing made 'from mixtures of the siho'atae of themetals indicated. Before that year Fraunh&fer andGuinand had made experiments modifying the com-position of crown and flint glasses, and had producedcompound lenses with a fair approach to achro-matism. In 1829, however, Dobereiner producedglasses containing barium and strontium, metalsclosely allied to calcium, the metal contained in lime,and in 1834 Harcourt, in England, commenced a longseries of researches on the production of new glasses^which—although the positive results obtained wereof small value—established principles subsequentlyturned to good account in the manufacture of specialkinds for thermometers, laboratory apparatus, lampchimneys, optical instruments, and many otherimportant articles. The next advance, an epoch-making one, was begun about 1880, when Schott, atrained chemist, the son of a Westphalian glass maker,was encouraged by Abbe* to search for new andbetter optical glass. His knowledge of mineralogyserved him well, for instead of proceeding laboriouslyalong the lines of methodical research, he took almosta direct road to the desired goal, producing glass con-


taining boric and phosphoric oxides with alumina andbaryta. Microscopes designed for these new glassesproved perfectly achromatic, and in every waysuperior to the older kinds ; and this striking advancehas doubtless contributed enormously to the useful-ness of the microscope, and of the microscope toindustry generally.

Schott next turned his attention to the solution ofthe problems of thermal expansion and volume tem-perature hysteresis of glass. Owing to its low thermalconductivity it is important that glass intended towithstand sudden changes of temperature shouldhave a thermal expansion as slight as possible, inorder to hold against the strain set up by unequaltemperature changes, and so that the risk of crackingmay be minimised witliin reasonable limits ; therange of temperature change varying inversely as thethermal expansion. Pursuing his investigations,Schott produced borosilicate glasses with exceed-ingly low coefficients of expansion, and capable ofresisting a sudden temperature change of over 190deg. Cent., whereas the ordinary Bohemian glasswould scarcely withstand a change of much over 90deg. The borosilicate glasses have therefore been ofservice for the construction of incandescence gaschimneys, and also of apparatus for laboratory use ;their slight solubility in chemical reagents constitut-ing an additional advantage.

When a thermometer made of ordinary glass is heatedto a temperature much above that of the air the glassbulb, on cooling, does not return immediately to itsoriginal volume, and may take months or even yearsto do so. Consequently if the bulb, before it has re-gained its original volume, is surrounded by meltingice, the thermometer will not register the true meltingpoint, but a point, varying with the thermometer, from0.5 to 1 deg. Cent, below the correct temperature ;and lower temperatures in general will not be regis-tered correctly until the bulb has regained its originalvolume. This defect was largely overcome by theresults obtained by Schott, whose Jena normal glass16 m and Jena borosilicate glass 59111, when used for


thermometers, show a zero depression of only about0.05 deg. Cent, after heating to 100 deg. Cent. Owingto their infusibility, glasses of this type can also beused for nitrogen-filled thermometers, registering upto about 575 deg. Cent.

The list of new and useful scientific products mightbe much further extended if we were to deal with thesubject more thoroughly, but it would be regarded asan oversight if we omitted to mention fused silicaglass, a comparatively recent invention. From purequartz worked in the oxy-hyclrogen flame excellentglass is produced, having the property of withstandinga sudden change of temperature of over 1000 deg.Cent. Being highly resistant to chemical action, ituseful in the laboratory for many purposes forwhich platinum was formerly employed.

Until the outbreak of war the production of glass-ware for use in chemical investigations was almostexclusively in the hands of Germany and Austria.Stocks were becoming speedily exhausted and theposition would have become serious for many impor-tant industries if British chemists had not promptlytaken the matter in hand. They had not merely toimitate glasses previously imported, but to findsubstitutes for certain ingredients of batch mixtures,notably potash, for which also we had hitherto beendependent on Germany and of which supplies wererunning low. The work of Professor Herbert Jackson*,in conjunction with the Glass Research Committee ofthe Institute of Chemistry, was especially successful,and, with the co-operation of a number of well-knownfirms, laboratory vessels, such as beakers and flasks,and all ordinary forms of apparatus are now producedin this country, having qualities in some respectssuperior to those of enemy origin. In some cases,perhaps, the products have not quite the same finishas those of the experienced German workers, but weare convinced that the defects are not radical, andthat given time, the British makers will not only equal,but excel the German in both quality and technique.

* Now Sir Herbert Jackson, K.B.E.


Inaddition to the needs of the laboratory, many otherkinds of glass were required, and the work wasextended to the investigation of over forty varietiesfor which formulas have been supplied to approvedfirms. With shortage of labour and other economicdifficulties, firms have undertaken with remarkableenergy new branohes of work which it is hoped theywill be able to retain, in the future, in the face ofcompetition from our quondam enemies.

Yet another problem, has been successfully tackledby Professor Jackson for the Ministry of Munitions,viz., the treatment of clay used for making vesselsemployed in glass production.

For the production of optical glass essential to theservices, we, fortunately, had well-established manu-facturers, by whose praiseworthy endeavours theoutput has been sufficient to cope with the greatlyincreased demand. Professor Jackson has suppliedformulas for batch mixtures for several importantvarieties not hitherto made in this country. Thodifficulty of securing supplies of suitable sand hadalso to be faced, and our mineralogists and chemistsdevoted attention to this question, with satisfactoryresults, the report of Dr. Boswell, of the ImperialCollege of Science and Technology, indicates that wepossess natural resources wliich can be utilised by ourmanufacturers to their advantage. Research workon refractories and electric furnace methods is alsoin progress at the National Physical Laboratory.

In the course of time an enterprising firm, with theaid of chemists and from indigenous sources, producedsupplies of potash of high quality in sufficient bulkfor the imperative requirements of glass makers, andthis factor was of no small consequence, since it isadmitted that for certain glasses potash is practicallyindispensable.

From the foregoing, it is evident that in spite ofthe antiquity of the industry, and the fact that goodglasses for ordinary and ornamental purposes wereproduced independently of modern science, manyspecial glasses owe their origin entirely to scientificinvestigation. I t is not too much to say that on tho

TO CHEMICAL vSCIENCE 75

possession of such glasses in time of war may dependthe fate of many a good ship and many a good man.Who can say, then, how great is the debt of theindustry to science and of the country to both ?

ENAMELS.The art of enamelling is of remote origin. We

have already referred to its application to pottery bythe Chinese. It was practised also by the Egyptiansand Etruscans, passing in the course of time to theGreeks and Romans ; but we propose to deal moreparticularly with the enamelling of metals, whichappears to have been invented in Western Asiaand to have traversed Europe in the early centuriesof the Christian era. The history of the subject isof absorbing interest to those who regard it as an art,and much may be gleaned from Bushell's work on" Chinese Art,'* published by the Board of Education.The Chinese give the credit for its discovery toConstantinople; the similarity between the methodsof the Chinese and the Byzantine enamellers is heldto support this opinion. We are concerned here, how-ever, with the utilitarian rather than the artisticapplications of enamels. We use them in the manu-facture of badges, watch and clock faces, and onsurfaces exposed to weather (advertisements), on theblades of exhaust fans, on baths and domestic utensils,and on vessels employed in chemical industry.

An ordinary enamel may be prepared from commonglass fused with lead oxide, and rendered opaque by theaddition of oxide of tin. Colours may be producedby the addition of other metallic oxides. Thus, fromcopper we obtain green ; from iron or gold, red, andfrom cobalt, blue. Small quantities of manganesedioxide give us a fine violet colour and larger quantitiesblack. For the production of good colours, thepurity of the raw materials is of the first importance,and the enamel maker looks, therefore, to the helpof the chemist to ensure satisfactory results. If anenamel is to be pigmented with copper, the presenceof this metal in the raw material will not be objection-able if its degree of oxidation is the same as that of the


pigment used. If the enamel is to be coloured green,with cupric oxide and that substance is present in thelead oxide used, the impurity is of small consequence ;but if the enamel is to be coloured yellow with anti-mony oxide, the green produced by the copperimpurity will spoil the effect. The presence of smallquantities of ferric oxide in the lime will modify thegreen produced by copper oxide, and is undesirableunless it be required to tone the green colour, whenit can be added to materials originally free from thissubstance. In any case, the quantity of impurityshould be estimated and duo allowance made forits effect. Much \may depend on the method ofpreparation of the pigment. For instance, cupricoxide may be prepared by roasting copper filings inair, but the product will not yield nearly such goodcolours as the oxide chemically prepared from purecopper ; and again, the blue colour produced fromcommercial cobalt compounds is greatly inferior tothat obtained from chemically prepared cobaltoussilicate.

Of the methods of preparing chemical and heat resist-ing enamel for industrial plant little is common know-ledge. In some cases the coating consists of twolayers, the first being devised to bind with the metaland act as intermediary between the metal and thefinishing enamel. Having in view the uses to whichsuch vessels are put, there is plenty of room forfurther investigation, particularly on the coefficientsof expansion of various metals and alloys and therelation of such physical considerations to thecomposition of the enamels employed. The surface

-rremains good until a craze appears, but once liquidgets to the metal the vessel begins to lose its coating.It is reassuring to know that chemical firms of longstanding find British enamel ware, such as evaporatingpans, at least as satisfactory as that from Germany,though our manufacturers, as is often the case withother commodities, have been less inclined to putthemselves about to supply special requirements, forinstance, with regard to the shapes and sizes of thevessels required.


CHAPTER XI.

POTTERY AND PORCELAIN.

THE manufacture of pottery is yet another"industrywhich has been handed down from very early times.Pliny attributed the craft, in which the Greeks andEtruscans excelled, to Conebus, an Athenian, butobviously it was of far greater antiquity, the potterbeing frequently referred to in ancient Egyptianrecords to symbolise the Creator of man. Theearthenware of the Greeks and Romans was unglazedand porous, but they rendered their vessels imperviousby covering them with wax, tallow and bitumen.The invention of porcelain is generally credited tothe Chinese. It is mentioned in books of the Handynasty, the earliest date suggested being about185 B.C. Its origin has been attributed to attemptsmade to imitate glass imported from Syria andEgypt., and by some it is supposed to have beendiscovered accidentally by alchemists in theirsearch for the philosopher's stone. The industrywas started in Japan before 27 B.C., and foundits way from the Far East to Persia, where it isknown as chini, coming to us, in the course of time,through Arabia, Spain, Italy and Holland, thepotteries of Lambeth being founded by men fromHolland about 1640. Porcelain was made in France, atSt. Cloud, towards the end of the seventeenthcentury, and in nearly all European countries inthe eighteenth century.

We can only marvel that such porcelain as, say,that of the Ming Dynasty (1368-1643), with allthe technique involved in the selection of materialsand its treatment, the craftsmanship, colouring andglazing, was produced before science, as we now usethe term, had any voice in such matters. The


Chinese hard paste porcelain consisted of kaolinin a pure and very finely divided state, and petuntze(finely ground felspathic stone); and the glaze wasmade from selected petuntze mixed with speciallyprepared lime.

One of the first European makers of fine porcelainof whom we have records was Botticher, a Saxonchemist who was placed in charge of the Meissenfactory, established in 1710, the methods employedbeing kept secret. Pott, a Prussian chemist, en-deavoured to compete with him, and although hisefforts were not successful, his researches on materialslikely to be useful in porcelain manufacture gainedfor the industry some helpful knowledge. Aboutthe middle of the eighteenth century 700 men wereemployed at Meissen, but in the meantime Stolzel,who escaped from the factory about 1720, foundedthe Austrian industry at Vienna, where 500 menwere employed in 1785. Mention should also be•made of the circumstance that William Cookworthy,chemist of Plymouth, to whom we have alreadyreferred in connection with cement, found kaolinat Tregonning, near Helston, and took out a patentin 1768, which he worked at Plymouth for two orthree years before establishing a factory at Bristol.We must admit that the claims of science so far wereslender, and we do not propose to pursue the historyof the subject further; but science required for herown purposes porcelain resistant to chemical action,heat, and variations of temperature. The productionof Royal Berlin basins and crucibles for the laboratorycould only be secured by careful selection andutilisation of the most suitable materials and muchpainstaking experiment. Science examined the pro-cesses employed and explained the changes involved,while one notable achievement, viz., the discoveryof means for measuring high temperatures, founddirect application in the industry. The temperatureof kilns is a factor of no little importance, and isusually determined by cones made of oxides of iron,aluminium, and silicon. The softening points ofthe cones are known with reasonable accuracy—a

TO CHEMICAL SCIENCE

series of thirty-six allowing for the observation ofsufficient range of temperature in porcelain burning.As the temperatures exceed 1000 deg. Cent, ordinarythermometric methods are not applicable. Theseries of cones could only be constructed and stan-dardised with the aid of physical science, which hasprovided Le Ohatelier's thermo-electric pyrometer,Callendar's platinum resistance thermometer and theFe"ry radiation pyrometer. Their use in the stan-dardisation of the cones, however, is, of course,insignificant compared with their use in metal-lurgical operations.

For supplies of porcelain for laboratory pur-poses this country has hitherto been mainly de-pendent, as in the case of glass, on Germany. Ourchemists have taken the matter in hand, however,and remarkable progress has been made by severalBritish manufacturers. Research on the subject ofhard porcelain is progressing, and there is good groundfor hoping that this branch of the industry will beretained here in the future.

The danger to workers of lead oxide as a constituentof glazes for earthenware has also provided a problemfor chemists. The employment of lead silicatesinstead of oxide, as suggested by Thorpe and Sim-monds, is less harmful; and the lead glazes havebeen largely superseded in recent years by mixturescontaining silica, alumina, potash, and soda, withabout 10 per cent, of boric acid to increase thefusibility. Where lead is an essential constituentit is applied in the form of silicate.


CHAPTER XII.

CHEMICAL PRODUCTS.

IN our second chapter we have dealt with theheavy chemicals and alkalies, and we will proceednow to consider the production of other chemicalsubstances of value in industry, or useful fordomestic, medicinal, scientific, or other purposes.The importance of this branch is so wide andfundamental that it is not too much to say thatindustry as a whole is largely dependent on anadequate supply of chemical • products. The fieldis so great that we cannot attempt to indicate allor nearly all the substances coining under this head,but we will choose a few examples of different types,all rendered available by scientific methods.

Acids.—Certain acids, such as tartaric, citric,lactic, oxalic, formic, salicylic, benzoic, acetic,hydrofluoric, boric, and arsenic acids are not preparedon a scale comparable with that of sulphuric, hydro-chloric, and nitric, but their value in technicaloperations and for other purposes warrants theirindustrial production in a condition more or lesspure, according to circumstances. Tartaric andcitric acids, from vegetable sources, and lactic acidof animal origin, are used in calico printing. Thefirst is an ingredient of baking powders and effer-vescing medicines, such as seidlitz powders, andthe second is used in the production of summerbeverages. Oxalic acid, which is prepared by heatingsawdust with a mixture of caustic potash and sodain the presence of air, is also used in calico printing,and its acid salts are valuable as detergents, underthe name of salts of sorrel or salts of lemon. Formicacid is useful in dyeing and tanning, and it is interest-ing to note that it was formerly obtained by distilling


red ants, but is now made by heating caustic sodawith carbon monoxide under pressure. Salicylicacid, which is prepared from phenol, is used in theproduction of various drugs, of which aspirin is anexample, and is employed as an antiseptic. Benzoicacid, from toluene, finds application in the manu-facture of dyes and as a preservative ; acetic acidin bleaching, dyeing, and calico printing, and inthe manufacture of artificial vinegar. Hydrofluoricacid, which is obtained by the action of sulphuricacid on fluorspar, comes on the market as an aqueoussolution in gutta-percha bottles, and is used foretching glass as well as for antiseptic purposes-Boric acid, from mineral sources, is valuable as aconstituent of various kinds of glass, and is used asan antiseptic and a food preservative. Arsenicacid is employed in dyeing and in the preparationof certain aniline colours.

Bases.—Among the common bases we have causticpotash, caustic soda—with which we have alreadydealt—strontium hydroxide, and magnesia,—alkalinemetallic oxides capable of neutralising acids with theproduction, by double decomposition, of salts andwater, the metals replacing the hydrogen in theacids. Caustic potash is prepared either by electro-lysis of the chloride or by the action of lime on asolution of potassium carbonate, that salt beingobtained from the chloride by a modification of theLeblanc process or by a method identical in principlewith the ammonia-soda process, in which trimcthyl-amine—of which something will be said later—takes the place of ammonia. For some purposesthe cheaper base, caustic soda, is equal in efficiencyto the more expensive but more powerful potash;but for others the latter is more economical—forinstance, in the production of oxalic acid from saw-dust on the large scale. When caustic soda aloneis used, the yield of acid is not more than a third ofthat obtained by the use of caustic potash or of amixture of potash and soda. On the other hand,in the analysis of flue gases, a valuable check onfuel economy, a soda solution of pyrogallic acid is


a very much more rapid and efficient absorbing-reagent for oxygen than a potash solution of thesame. Caustic potash decomposes most metallicsalts, and at a high temperature acts with energyon many substances. It is employed in numerousindustrial operations, and is ordinarily used for themanufacture of soft soap, in which it is combinedwith the fatty acids derived from the drying oils,such as linseed, whale, and seal oils.

Strontium hydroxide, prepared mainly from themineral sulphate, is largely used in the extractionof the uncrystallisable sugar from molasses. Thenative carbonate requires a higher temperature forcalcination to oxide than does calcium carbonate tolime. However, in certain sugar works, where fuel,including exhausted cane, is cheap, this process isused for the production of the material.

The use of maguesia in the ammonia-soda process,and also as a refractory material, has already beenmentioned. Considerable quantities are consumedin medicine as an anti-acid.

Salts.—The salts of technical importance are verynumerous. Those of sodium, on account of theircheapness, easy solubility in water, and comparativeharmlessness, are in constant use in many in-dustries, and are often interchangeable withpotassium salts; but in some cases the specialproperties of the latter yield better products formanufacturing purposes. Potassium permanga-nate and chlorate can be crystallised betterthan the corresponding sodium salts, and aretherefore obtainable in a higher state of purity.Potassium nitrate is used in the manufacture ofordinary gunpowder, whereas the use of sodiumnitrate would be impracticable on account of itsready absorption of atmospheric moisture. Potassiumsulphate, a constituent of ordinary alum, occurs asthe mineral kainite, and is valuable as a fertiliser.Potassium f errocyanide and bichromate are ingredientsin the production of certain pigments, and the latterfinds employment in tanning and photography, aswell as in the cells of bichromate electric batteries.


Both these salts are now largely replaced by thecheaper sodium compounds, owing to the stoppageof supplies from Germany. A mixture of sodiumand potassium cyanides obtained by heating potassiumferrocyanide with metallic sodium is used in theMacArthur-Forrest gold extraction process. Sodiumnitrite and hypochlorite are largely usod in the pro-duction of dyestuffs, and, indeed, the fact that theformer was hitherto obtained almost exclusivelyfrom Germany formed no small obstacle to themanufacture of certain important dyes in this country.Sodium thiosulphate—hypo—is used in bleachingas an antichlor and in photography as a solvent forsilver halides. Sodium silicate—water glass—is usedfor preserving eggs and also for protecting carbonatestone buildings from the action of weathering.

Ammonium sulphate we have already mentionedas an artificial manure. The chloride is used insoldering, and its solution forms the electrolyte inLeclanch6 cells. The nitrate is the source of " laugh-ing gas," and the commercial carbonate is commonlythe principal constituent of " smelling salts."

Mention must also be made of certain peroxycompounds, some of which have attained considerabletechnical importance in comparatively recent times.Sodium peroxide is obtained by the action of hot air onsodium contained in aluminium trays. The per-carbonates and persulphates of sodium, potassium,and ammonium are prepared by methods of electro-lysis. Barium peroxide is made by heating theoxide to a dull redness in dry air, free from carbon-dioxide, and is used in the manufacture of hydrogenperoxide, which, as are other peroxy compounds, islargely applied as a bleaching agent for cellulosematerials.

The salts of barium and strontium are very usefulin pyrotechny, the former for producing green andthe latter red light. Magnesium sulphate is Epsomsalts. Mercury salts, including calomel, are also em-ployed in medicine. Morcurie chloride or corrosivesublimate is an excellent antiseptic, and the fulminatois a useful explosive. .Zinc chloride is used for the*

a

84 WHAT INDUSTRY OVVWS

destruction of insects and parasites, mid other zinccompounds are of medicinal value. («old, silver,and platinum Halts aro extensively used iu photo-graphy, arid copper, tin, and antimony Halts indyeing and calico printing. Copper salts nro alsoimportant in the Deacon chlorine proems, in olootro-typing, in tho manufacture of pigments, and thoprotection of wheat from smut. Load carbonate,or white lead, is used in largo quantities in paintmanufacture, and tho a/Ado is an explosive body,which may bo employed in percussion caps. Bismuthand iron salts find good use in medicine, tho sulphateof icon being also useful in gold extraction.

Solvents.••- -Water, the commonest and most usefulsolvent, cannot bo discussed hero for tho obviousreason that under ordinary conditions it is not uchoxnical product from our point of view. Waterpurified by distillation, however, is a commercialarticle, and might perhaps be included. Amonginorganic solvents, mention must bo made of ammo-niacal copper solution for cellulose, and sulphurchloride, which is prepared by the direct union oftho elements and is a valuable solvent for sulphur,being largely employed in vulcanising rubber. Thocommon acids, such as nitric;, sulphuric, and hydro-chloric, tiro excellent solvents for metals and oxidow,but tho solutions HO obtained aro not simple, thooriginal metal or oxido not being recoverable byinoroly evaporating tho wolvont. Alcohol, or spiritsof wino, prepared by tho rectification of fermentedliquor, in a valuable solvent in many ways, such an,for instance, tho purification of certain organic pro-ducts by crystallisation from alcoholic solution.

In manufacturing processes, substances, nuch asfatty oils, rubber, and sulphur, which aro insolublein water, aro frequently roquirod in tho formof & solution, and it rontw with tho ehotniHt todiscover the bout solvents for such HubstancoH andtho mothod.s of proparing and applying thorn.Oarbon diaulphido, a volatile, poisonous, highlyrefracting liquid, hoavior than water, wan dineovorodin 1790 by LampudiuH, who obtained it by diHtilliixg


iron pyrites with carbon. As ordinarily met withit has a most obnoxious smell, but when pure theodour is ethereal and not unpleasant. I t occursin the products of the destructive distillation of coal,but is manufactured mainly by the direct union ofcharcoal or coke with sulphur in retorts or in theelectric furnace. Its uses are many; it dissolvessulphur, gums, rubber, phosphorus, resins, essentialoils, iodine, and alkaloids. I t is used sometimes forthe extraction of fatty oils remaining in the residueafter crushing seeds, being subsequently removed bydistillation and used again. A solution of sulphurin carbon disulphide is used for the vulcanisa-tion of rubber. Its poisonous action has beenutilised for destroying blight in grain without illeffects—except to the blight; and potassium thio-carbonate—a compound of carbon bisulphide andpotassium sulphide—is destructive to insects whichinfest vines. On account of its high index of refrac-tion, hollow glass prisms filled with carbon disulphideare employed in spectroscopy. A solution of iodinein carbon disulphide is of use in certain physicalexperiments, for the reason that such a solution isopaque to rays of light, while it transmits heat raysfreely. Lastly, we may mention that from carbondisulphide and chlorine is obtained carbon tetra-chloride, a solvent for fats, which is also employedin the production of certain dyes, and being non-inflammable, serves a useful purpose in fire-extinguish-ing apparatus.

Among the organic solvents are several that are alsoanaesthetics. Chloroform was discovered simultane-ously by Guthrie, an American, and Souberain, aFrenchman, in 1831, and was first employed as an anae-sthetic by Lawrence in London, and Simpson in Edin-burgh, in 1847. It is prepared on the large scale by theaction of chloride of lime on alcohol or acetone, theproduct being a valuable solvent for fatty oils, india-rubber, alkaloids, resins, and other substances.Prepared by the above process, however, it containshighly poisonous impurities, which are gravelydetrimental to its use as an anaesthetic, for which


purpose it is obtained by distilling chloral—resultingfrom the action of chlorine on alcohol—or its hydratewith caustic soda, the final product being sufficientlypure.

Ether, another solvent, also an anaesthetic, wasknown in the sixteenth century, and described byValerius Cordus, a German physician. It wasprepared by the action of sulphuric acid on alcohol,and in the early part of the eighteenth century wasemployed as a mixture with alcohol, under thename of Hoffmann's Anodyne, to allay pain. Itsuse as an anaesthetic was discovered by CharlesJackson, of Boston, in 1842. The most economicalmethod of manufacture is the continuous process>devised by Boullay.

Acetone, a valuable solvent for oils, and employedlargely in the manufacture of explosives, is foundin the free state in the products of the destructivedistillation of wood, and is obtained by the drydistillation of acetate of lime, which substance isalso produced from pyroligneous acid.

Fine Chemicals.—The many substances we havementioned under the heading of chemical products,represent only a very small proportion of those incommon use, and do not include all that are employedin the laboratory, or those at present of purelyscientific interest, which are very numerous. We say" at present " purposely, for no one can tell how soonthey may. find practical application. The value of" research for its own sake " has already been shownin the many examples we have cited of the discoveryof elements and compounds, at first merely regardedas scientific curiosities, but sooner or later proved tobe of incalculable importance to industry and to theworld. So much depends on the accuracy ofanalytical results, that an adequate supply ofchemicals in a sufficiently pure state to be used asreagents is an essential requirement in all laboratories.The statement should be too obvious to mention, butit must be remembered that we buy and sell onanalytical data; we check and control vast technicaloperations on such data, and must be able to rely on


sound reagents in most chemical investigations.German fine chemicals have enjoyed a reputation forpurity, but of chemicals generally, apart from dye-stuffs, we produce the bulk of our own requirements ;our export trade has been greater than that of ourcontinental competitors, and there is no doubt that,with increased scientific control and care, we canmanufacture products of equally high standard.

A number of concerns of established repute are nowenergetically developing the fine chemical industry.The processes of manufacture and purification callfor the services of highly trained chemists, of whomthe supply will certainly be forthcoming as the demandfor them increases.

A pamphlet prepared by a special committeeappointed by the Councils of the InstiUite ofChemistry and of the Society of Public Analysts, wasissued early in 1915, giving details of the tests forpurity of a number of important analytical reagents.This provides a standard for the manufacturers whowill still continue to make products of other gradesfor various uses, while producing the fine chemicalsup to the specification standard at a higher cost,which the consumer is always willing to pay. Forone example out of many, sulphuric acid for manytechnical purposes is highly impure. In some casoathe impurities are substances which do not affect thebehaviour of the acid and its suitability for the purposesfor which it is required. A purer acid is made forgeneral laboratory use ; but for good analytical worktho acid must be free from lead, calcium and othermetals, from arsenic* selenium, nitrogen and halogencompounds, and from reducing substances, and shouldleave no solid residue on evaporation to dryness.Tests are prescribed whereby such impurities maybe detected, but it is most advantageous to be ableto securo reliable supplies without the necessity ofapplying them, and possibly being obliged to purifythe substances in the laboratory before using them.The purification of sulphuric acid on the small scaleis an expensive, difficult, and tedious operation. Itis a hopeful sign therefore that a number of our well-


known manufacturers are now producing guaranteedanalytical reagents of recognised standard degreesof purity.

Drugs.—After all the references we have made tothe work of the chemist in industry, we do not needto labour the distinction between the man whopractises chemistry and the man who practisespharmacy. Tho latter has to depend on the formerfor many of tho materials he employs in dispensing,or tho physician may prescribe with very uncertainresults, and the patient perish, or, in any case, pay tono purpose. The subject of drugs and pharma-couticalH, with all its ramifications into the substancescompounded into medicines of all kinds, pills, powders,ointments, lotions, tinctures, and so forth, is tooextensive for us to treat adequately, and we can onlydeal with the subject by indicating a few develop-ments in this important branch of industry.

Many of the drugs used in medicine are of vegetableorigin. Quinine, for instance—discovered in 1820 byPelletior and Cavontou—is extracted from the barkof trees of the Cinchona species. Stryclinine isobtained from tho seeds of various plants such asStryclinos mix vomica. Atropine is prepared fromdeadly nightshade juice, winch contains two alkaloids,hyoscyamino and hyoscine. The juice is treated withcaustic potash, the hyoscyamine being thereby con-verted into atropine. The mixture is shaken withchloroform and tho solvent evaporated, the atropinebeing extracted with dilute sulphuric acid, precipi-tated by potassium carbonate, and re-crystallised fromalcohol. A solution of the alkaloid has the property,when placed in the eye, of dilating the pupil, a mostuseful aid to the ophthalmic surgeon.

An increasing number of useful organic drugs,including alkaloids, is now made synthetically fromother chemical substances. Many of these areunknown in Nature, their production and utilisationbeing solely due to science. Salicylic acid and itsderivatives, including aspirin, are made from phenol,and used extensively in the treatment of rheumaticand nervous disorders. On account of certain objec-

TO CHEMICAL SCIENCE S9-

tionable physiological properties, attempts have been,and are being, made to obtain other derivatives thathave no such disadvantages, and good results havebeen obtained with aeetylsalicylic anhydride andcinnamoylsalicylic anhydride. The antipyretics,phenacetin and antifebrin, are made from phenol;antipyrene, which is put to similar uses, being theproduct obtained by methylating tho pyrazolonderivative formed by tho condensation of acetoacetieester with phenylhydrazine. Derivatives of a,ntipyrenoinclude salipyrene and tolypyreno. Veronal is-another synthetic drug.

The use of metallic compounds, as bactericidalagents, has long been known. Compounds of mercuryhave long been used in the treatment of certain dis-eases. Recently the researches of Ehrlich on theorganic compounds of arsenic have done much toalleviate suffering, such complex bodies being muchless poisonous to human beings than, are the simplercompounds of arsenic. Salvarsan and neosalvarsanhave met with success. One of the simplest of suchderivatives, atoxyl, has been used in the treatment ofsleeping sickness.

Local anaesthetics, administered hypodermically,include cocaine, novacaine, and stoveine, the firstbeing extracted from the coca plant by alcohol acidi-fied with a small quantity of sulphuric acid, and thetwo latter being synthetic products.

Among antiseptics we must again mention phenol(now being manufactured from benzene in largo quan-tities for making explosives), cresols, formaldehyde,mercuric chloride—corrosive sublimate—and boricacid ; while as disinfectants and insecticides, bleachingpowder, carbolic acid, potassium permanganate,naphthalene, and zinc chloride—all chemical products—are now largely used.


OHAVTKU- XIII.

PHOTOGRAPHY.

THIS beautiful and now almond essential art isdependent upon tho action of light on variouschemical compounds, principally tho HaltH of silver.It was first observed by Boyle about tho middle oftho seventeenth century, that luna amwa* silver<:hlorido—darkens on exposure to light, and thinphenomenon was further investigated by tho Swedishchemist, Scheclo, in, 1784. No attempt, however,was made to utilise thin property for tho productionof pictures until 1802, when Thomas Wedgwoodobtained prints of loaves and other ilat bodion onsensitive Hurfac<w pnipanul 'by moistening whitoleatluw or paipc i1 with silver nitrate solution. Similarexperiments wore carried out by Sir Humphry Davy,but tho pictures produced lacked one importantadvantage ; they were not permanent in daylight, andtherefore had to bo kept in tho dark and examinedonly in weak, artificial light. The next workers ofnoto wore Niopco and Uaguerre, a groat advancebeing made by the latter, when, in J8.'M, ho introduceda new departure, well-known as tho daguorrotypoprocoHH. This was long ago superseded by other andbettor methods, but it served the purpose of indicatingtho right road to success. A plate of polished silverwas exposed to the action of iodine vapour, beingthereby covered with a him of silver iodide. Onexposure in a camera no apparent change look placeuntil development, as is tho case with modernphotographic plates. Tho method of developmentof the Daguorro plates was an accidental discovery.Dagiifirro, while experimenting, was called away justafter ho had removed a plate from his camera. J^orflafoty, he put tho plate in tho first dark place that


caught his eye—a box containing odd pieces ofapparatus—and when he returned to continue thework, he was surprised to find that during his absencethe image on the plate had developed. Investiga-tion of the contents of the box led to the final con-clusion that the agent was some metallic mercuryloose in the bottom of the box. This provided themeans of development, the plates after exposure tolight being acted upon by the vapour of mercury.The image was made permanent by dissolving theunaltered silver iodide in the parts less affected bylight with a hot solution of common salt, an improve-ment being almost immediately effected by thesuggestion of Herschel, that sodium thiosulphate—" hypo "—was a more suitable fixing agent.

Meanwhile, other investigators had not been idle.In the Calotype or Talbotype process, elaborated byFox Talbot, and introduced in 1841, we find theprinciple of modern photography showing signs ofactive germination. The method depended entirelyon the use of papers sensitised with chloride andiodide of silver. In his earlier researches, a piece ofpaper was covered with silver chloride by immersion,successively in solutions of common salt and silvernitrate. Prolonged exposure in the camera resultedin the production of a negative image, which could befixed by common salt solution. This method wassoon afterwards greatly modified in the following way.The image formed b3r the camera lens was receivedon a sheet of paper covered with silver iodide, and wassubsequently developed by a mixture of silver nitrate,acetic acid, and gallic acid. When the resultingnegative was made transparent by means of wax,positive prints could be obtained by allowing sunlightto pass through the negative on to a piece of the sensi-tive silver chloride paper. The first use of glassplates was made by Archer in 1851, the glass beingcovered with a film of collodion in which cadmiumor zinc bromide or iodide had been dissolved. Theplate was sensitised by dipping into a solution ofsilver nitrate and it was exposed in the wet state in thecamera, the image being developed by washing with

1)2 WHAT INDUSTRY OWKK

sonio reducing agent, such as forrous sulphate. r.l.'11<>imago being fixed by a solution of sodium thiosulphateor potassium cyanide provided, when tlried, a negativefrom which any mimbor of positive prints could botaker). 1W this means the detail of tho pictures wasbottorthant.bat given by tho older processes, and otheradvantages wore obtained, including tho shortenedtimo of exposure of tho more sensitive collodion film..By this timo very many workers had entered thefield, and tho art made rapid strides. A furtherimprovement was the introduction of dry plates, thosensitive surface being composed of gelatine impreg-nated with silver bromide; but to give a detailedhistory of the development of modern photographywould he beyond the scope of this article.

The modern dry platen consist of sheets of glasscut to standard U'VAO and covered with a gelatineemulsion of Rilver bromide. The emulsion is preparedby the inter-action of amrnoniaeal silver nitrate withCXCQRR of potassium bromide containing a little iodidein hot gelatine solution, the emulsion formed beingkept at a temperature of 45 riotf. Cent, for some time-an operation which increases the sensitiveness. Theemulsion is thon was lied free from soluble salts, runin an oven coating on to tho plates, and dried. Afterexposure, the plates are developed by the* reducingaction of certain compounds, such us pyrugallio arid,hydroquinono, motol, ferrous o.\ala1<\ and others, withvarious mibstances added to modify favourably (.hocourse of development. Tho developed plates arefixed by means of a solution of sodium thiosulphato,well wrtHhod and dried. Tho introduction of celluloidfilms has lessoned the inconvenience attached to thobulkinoHs and rigidity of plates, films being invariablyused when compactness and lightness of outfit arerequired.

Many kinds of printing paper are available attho present time. Silver chloride papers, bothin gelatine and collodion, are used for daylightprinting, <$rdinary I*.O.I*, being toned with a solutioncontaining * gold chloricIo before fixing with hypo.Soli-toning papers require washing and fixing only,


the paper already containing tho necessary gold, butmodifications of tone may be obtained by washingthe prints in a solution of common salt before fixing.Silver bromide and silver iodide are the sensitivebodies in. bromide and gaslight papers, of which manyvarieties are on the market, these papers requiringdevelopment, as in the case of plates. Beautifultones may be obtained by platinotype papers.

Other methods of printing include the carbonprocess, depending upon the fact that when a gelatinesolution of potassium bichromate is exposed to light,the gelatine becomes insoluble in water. Brilliantblack and white prints may be obtained by theadhesion, after washing, of finely divided carbon tothe insoluble gelatine surface. The paper for theblue prints familiar to engineers is prepared by immer-sion in a solution containing potassium ferrocyanideand ferrous ammonium citrate, the prints merelyrequiring to be washed in water and dried. Othermethods have been devised to obtain engineers3

prints in various colours on a white ground, but formost purposes the blue print method is adequate.

Colour photography, which has attracted muchattention during the last few years, has been developedwith some success. Many processes have beendevised, one of the most striking being the mirrormethod of Lippmann, which depends \ipon thointerference of direct and reflected rays at differentdepths in the film, the ultimate deposition of metallicsilver produced by development occurring at a distancefrom the reflecting surface fixed by the wave lengthof the impinging light. On viewing the developedand fixed plate similar interference phenomena takeplace with the consequent natural colouring of theimage. With the aid of orthochromatic and of pan-chromatic plates, prepared by the uso of variousdyes, combined with screens or colour filters, excellentcoloured photographs may be obtained. Three-plate and single-plate processes are available, tho :latter type being more convenient. The Lumiereprocess is a single-plate process, in which the screenconsists of a mixture of starch grains, dyed red,


green, and blue, incorporated in a single layer in theplate. All these colour photography processes,however, are still somewhat expensive.

Mention could be made of many debts to photo-graphy, including the discovery of radioactivity,which was directly due to the sensitiveness of thephotographic plate, the discovery of stars too faintto be observed by the most powerful telescopes, theinvention of photo-mechanical processes employed inillustrating books and journals, photomicrography andits numerous applications, and the cinematograph,apart from its everyday uses in peace and war.

Photographic Materials.—The manufacture ofphotographic materials is essentially a branch of thefine chemical industry, since the production of goodresults depends as much on the purity of the materials

'"employed as on the manner of employing them.Developers, such as pyrogallic acid, metol, and hydro-quinone, toning solutions containing gold chloride,and the materials for making and sensitising plates,films, and printing papers must necessarily be pure.In fact, the whole art of photography depends, fromstart to finish, on a high order of scientific work, bothchemical and physical.


CHAPTER XIV.

AGRICULTURE AND FOOD.

AGRICULTURE.AGRICULTURE, though primarily concornec^with the

cultivation of the soil—tillage, pasturage, andgardening—may be regarded as the industry towhich we look, not only for food—animal andvegetable—but, directly or indirectly, for clothingand textiles, timber, drugs, leather, rubber, and a hostof other necessaries and comforts. Little reflectionis required to show that agriculture is dependent onscience, and, although many practical farmersstill scout such ideas, the various branches of theindustry owe much to geology, biology—botany andzoology—chemistry, physics and meteorology, as wellas to the art of engineering. We propose to refer,briefly, to the work of the chemist, especially inconnection with the subject of fertilisers.

The fear has been expressed from, time to time that,even making allowance for the effects of war, the pro-duction of food will fall behind the needs of theincreasing population of the earth, unless sciefto&wcandevise measures for coping with the problem. Wehave shown how, through science, fields devoted tothe cultivation of indigo and madder have made wayfor cereals, and we may confidently expect furtherchanges of the same kind, or even find, in the labora-tory, means for obtaining food independently of theprocesses of Nature by reproducing something akinto the vital processes of vegetable and animal life.

Fertilisers.—Mother Earth readily repays the kindlyattentions of man and offers an illimitable field toscience in the development of food supplies for manand beast. The chemist examines the soil, decidesthe means to be adopted for the restoration of its.

00 WHAT INDUSTRY OWKS

fertility, and burron land is thereby reclaimed.Natural manures, through tho agoney of which thosoil regains its creative on orgy, are supplomontod byartificial fertilisers, and tho yiold of foodHtufi's isincreased. Thus, sodium nitrato, found in enormousdeposits in certain parts of Wostorn South America, isvory largely used aft a nitrogenous manure, tho crudematerial being purified by (crystallisation. Potassiumsulphate, in tho form of tho minoral ki<vr.s(iri(1(ourichos tho soil dofioiont in potash. Atumoninnxsulplmto, from tho distillation of coal and Nhalo, inanothor valuahlo nitrogonous manuro, and HU]'>OI*-phosphato of linio, ]>r(Nj>aro<l by tho action of sulphuricu«i(l on jninoral phoHpliat(is, providoH a fiU'tiliHorcontaining a largo proportion of solublo phosphato.TliO manufactui'o of this Kubntanoo, nioroovor, hashoou largely instrumontal in k<M>])ing alivo tho loadoihtiHibor ))i'oc.(vss—chamlxvr acid, as sucli, boing suit-ablo for tho purposo.

r.V\ui (calculation of Vorgara that tho South Americansodium nitrato bodfl would !.><> oxhauntod }>y thoyoar 1023 has boon provod to bo orronoous. Survoy.sof tho known, bods nhow that tho supply from thornwill bo isufTiciont to nuMit tho incroasing (h^nuind fortho noxt fifty years or more, whilothogonoral (thitructoi*of tlu^ country loads to tho roasonablo suppositionthat othor bo<ts of vast oxtont < xist and will bocapable) of supplying tho noodn of tho world for aiurthor 200 y<«trs. .llowovor, tho ond IUUHI, comoHoorior or later, and in, view of tho importance of thinsubBtanco, both as a fertiliser and as a startingmanorial in. tho lumiufaeturo of potansitun, nitrato,nitric acid, and othor xiitrogon compounds, thopro.spocti.vo sh()rta-g< lias given an impottis to researchwith tho object of utilising tho nitrogen in tho air.One of the methods employed aims at the preparationof nitratcH by heating air in. a specially constructedelectric furnace in which, by a Huitablo arrangementof oloctro-inagnots, tho arc is caused to asnumo a(UBCOUH shape. Tho oxide of nitrogen produced islod away to an oxidising chamber, whore it is convertedby atmosphoric oxygon into a higher oxide, which is

TO (MIKMIOAL SriWNOK! 1)7

absorbod by bason such as lime, nodn., potash, orammonia. Tho process, primarily discovered by SirWilliam Crookos, watt adapted by MoDougall ainl.Bowles, hi America, and Jat.or by Birkoland and Klyde,in Norway, where ohsotric powor in ehoap, and ba.soN,manufactured in. Germany, woro sent l.o Norway androtxxrnod as nit.rcit.oa.

Tlio cyanami do process, which forms a groatGorman industry, consists in heating calcium carbidewith nitrogen in tho ( ( c.tric. furnnco. Tho nil.ro^ori38 obtaino(I from liquid air by boiling off tho oxygon,or aw roHiduo from, wal-or gaH or producer gan, whichhas boon iiHod in tho manufaoturo of hydrog<ui. Tliocyaxuvmido in af)plicul diroctly as n maiutro, anil onoxpoBuro to w'ator at ordinary tomporatun^ HlowlyovolvoB amrtxonin., which, inxlc r l\w action of nitrifyingbacteria, in converted into comjxnindH of nitrogenroadily abrtor})(ul by tho plant. !It may ))o iiot-od a.lH<>that ammonia is easily formed by heating calciumoyanamido with water under pressure. K bariumcarbide in uwed instead of the calcium compound, tlxomain yield is barium cyanide, a convenient startingmaterial for tho manufacture of other cyanidoH.

Nitridett, such as those of magnesium, boron,~*milvsilicon, aro j)repar(ul in. the electric furnace, and findapplication as manures rich in nitrogen and as sourcesof ammonia, though their cost of production, is ratherhigh. Many other processes have boon patented andusod for tho fixation of nitrogen, and British chemistshave not boon idle, in spite of the difficulty of com-peting agairist the lower cost of power in othercountries. Water powor, abundant in Norway, isroadily converted into electricity, and is, therefore,a most valuable possession, in thin connection ; butwo are assured that an earnest endeavour in boingmade to produce nitrates in this country at tho presenttime. Incidentally, wo would remark that thofixation of nitrogen in of such importance thnt it ispractically certain that if Germany had not solvedtho problem before tho war, nho could not havemaintamod for HO long the sxipply of umnitionH to herarmy.


Basic slag—the phosphatic slag from the Thomasarid Gilchrist basic Bessjsmer process—when finelyground is a useful manure for certain purposes, grassland especially deriving- benefit from its application.Its employment in±. otlaer directions has not, so far,been extensive^",possibly owing to the existence of asomewhat arbitrary standard of valuation. It isdesirable that careful experiment should be madewith various crops to ascertain if this standard isreasonable for all purposes. In the result it is notunlikely that great dumps of slag, hitherto regardedas waste, both from the basic Bessemer and from thoopen-hearth processes, may be available for agri-cultural purposes.

The quality of artificial fertilisers is to some extentsafeguarded by the provisions of the Fertilisers and.Feeding Stuffs Act, under which the seller of anyartificially prepared or imported fertiliser, and anyartificially .prepared feeding stuff, is required to give awarranty to the purchaser as to the constituents ofvalue in these articles, and an undertaking that the per-centages found in these articles do not differ from thosestated in the invoice, beyond certain prescribed limitsof error. Official agricultural analysts and samplersare appointed to assist in the administration of theAct, and the Board of Agriculture is empowered tomake regulations for the purpose of carrying the Actinto execution. It is generally agreed, however, that,with few exceptions, the county and borough authori-ties concerned have practically ignored it, and beyondappointing officials as required by tl& Act have giventhem little or nothing to do, so that offending tradersare rarely brought to justice.

Feeding Stiiffs.—Among the principal artificiallyprepared feeding stuffs for cattle and sheep may bementioned cotton cake and meal, which are very richin albuminoids, as are also cake and meal from theground nut and Chinese soya bean, and linseed and rapecake, prepared from the marc or refuse from crushingfor oil. Other industries provide food material, suchas brewers' grains, malt dust and yeast, and beetsugar fibrous wastes.

TO CHEMICAL ..rSCBHSFGB"" 99

While, as we have indicated Vabove, the measurestaken to assure the quality^ij<!fo\d for cattle are, toa large extent, ineffective, tlii(>sec|bafee i in respectjofour own food are certainly m o r ^ j ^ ^ ^ t ^ i ^ f t h ^ ^the Sale of Food and Drugs Acts n l^4^^^^^\ | l i ? I r T

tage, be more thoroughly administered in* some partsof the country. The term " food " includes everyarticle used for food or drink by man, other thandrugs or water, and any article which ordinarilyenters into, or is used in, the composition or prepara-tion of human food, and also flavouring matters andcondiments ; the term " drug " includes medicinesfor internal or external use. Public analysts areappointed to examine samples—chiefly milk anddairy products—taken under the Act, and proceedingsfrequently follow both in the interests of health and ofthe prevention of fraud. Some may protest that thework of the public analyst is not in the interests ofindustry, but it must be admitted that the honestvendor is directly protected by the prosecution of thefraudulent, and it should be noted also that manyprepared foods, such as biscuits, cocoa, margarine,preserved meat, fish, fruits and vegetables, jams andconfectionery, and beverages are produced underscientific supervision.

The methods of preservation of perishable foodproducts are due to the application of science. Thesterilisation by boiling of meat and of fish, followedby immediate hermetic sealing in cans, is the resultof a knowledge of the nature of bacterial life, as alsois the practice of preserving by the application ofcold, the meat or fish being either-actually frozen, OJP-maintained at a temperature near the freezing pointwithout actual congelation. We will refer again tothe subject of cold storage later.

The law governing the sale of milk in thiscountry enacts that the content of fat (cream)shall be not less than 3 per cent. The variouspreservatives available for use are either prohi-bited, or are restricted as to the quantity that

H


may be added. This is a necessary precaution, asmost of the preservatives, such as formalin and boricacid, are not desirable from the point of view ofhealth, especially in the case of milk, which is soimportant to infants and invalids. The sterilisationof milk by pasteurisation, which consists in prolongedheating at a moderate temperature, is a useful meansof safeguarding the public health, the tasto, andtherefore the palatability, of the milk being very littleaffected by the treatment.

Science provides the moans of distinguishingbetween genuine butter and the various substitutesnow in common use, such distinction being necessaryfor the detection of fraud.

Careful investigation by botanical workers, com-bined with the proper application of manures, hasgreatly increased the yield of cereals, and the cultiva-tion of many other foodstuffs, such as roots, fruits,tea and coffee, comes more and more undor scientificcontrol, with beneficial results. Wo propose now toconsider, as an example, an important foodstuff, inthe production of which chemical, botanical andmechanioal sciences have played no mean part.

SUGAR.Sugar is contained in the sap of many trees, such as

the date, palm, and the maple, and in nearly all fruits.The main sources, however, are the sugar-cane and thobeet. The extraction of sugar from cano is said tohave been practised in Bengal and in China about800 B.C., and existing records indicate that tho Egyp-tians, Arabs, and Persians were acquainted with canosugar over 1100 years ago. Tho cane is now culti-vated in the West and East Indies, in the SouthernStates^and in South America.

In the old method of manipulation tho cane, whichcontains up to 18 per cent, of its weight in sugar, wascrushed between rollers, tho oxprossod juice treatedwith milk of limo to neutralise acidity, nlterod andevaporated to obtain tho crystals. The solid wasseparated hy drainage in perforated casks, and thomother liquor—which contains various substances


which prevent complete crystallisation—appeared onthe market as treacle or molasses, or was fermented tomake # rum. With modern mechanical and chemicaldevelopments the industry has been brought to astate of great efficiency. The introduction of evapo-rating pans and similar plant has effected markedeconomy in fuel; the crystals are separated bycentrifuges, resulting in great saving of time, and aleaf has been taken from the book of the beet sugarmanufacturers by the employment of a diffusionprocess to replace the crushing. The cane is shreddedand soaked in water, the sugar diffusing through thecell walls of the cane into the water, and the yieldis enormously increased.

The process of refining crude sugar generallyconsists in dissolving it in hot water—blood beingadded to very crude sugars to carry down impuritiesin coagulating—filtering, decolourising by the actionof animal charcoal, and evaporating to crystallisation.The products are separated into various gradesaccording to purity. As an instance of the valueof scientific control in sugar-refining processes, wemay mention that one concern has for many yearspast effected a saving of between £75,000 and £100,000a year as a return for an expenditure of £20,000 ayear on its laboratories and staffs of chemists.

Sugar was discovered in beetroot by Marggraf, aGerman chemist, in 1747, but it was not until 1801that a factory was established for its extraction,the first being erected in Silesia by Achard. Inthe light of present-day events it is interesting toobserve that the German industry received consider-able impetus in its early years through the landblockade of Prussia, enforced by Buonaparte, whichmade the home production of sugar a necessity.Buonaparte also gave encouragement to the estab-lishment of the industry in France, and it is nowcarried on in Russia, Holland, and other Europeancountries. The juice of the common beet containsonly a low percentage of sugar, but by carefulscientific cultivation the yield has been steadilyincreased, so that some varieties give over 15 lb.

H 2


of sugar per 100 lb. of beet, instead of about 6 1b. orless. The yield of beetroot from the land has beenincreased by about 15 per cent., and the coal con-sumption in the process of extraction has beenreduced by about 80 per cent* The exhausted sub-stance is utilised for making feeding stuffs for cattle.In the early method of extraction the roots werecleaned and shredded, the shreds placed in woollen,bags, and the juice squeezed out by hydraulicpressure. This practice still prevails in some places,but has been replaced in others by the cleaner andmore efficient diffusion process. The roots arecut into thin strips which are exposed to the actionof water ; the sugar diffuses out into the water,leaving colloidal substances in the cells, the wallsof which are impervious to colloids. The treatmentof the juice is similar to that employed in the casepf cane sugar, the yield of crystallised sugar beingabout 70 per cent, of the sugar in the root, the other30 per cent, remaining in solution as molasses ortreacle, to be sold as such or used to make rum.

Increased yields of sugar in the crystallised state,from both cane and beet, are largely attributableto the Osmose process, based on Graham's workon dialysis, and.the Elution processes elaborated bySteffen and by Scheibler. In the first process thesugar is allowed to diffuse through a parchmentmembrane into pure water, the substances which,prevent crystallisation being unable to pass throughthe membrane. The solution obtained is then workedup for sugar and for potassium nitrate which accom-panies it, while the remaining liquor goes to thedistillery for the manufacture of by-products.

The Elution processes depend on the formation ofthe sparingly soluble calcium or strontium saltsformed by sugar—calcium and strontium saccharates.These salts, obtained by various methods in purecondition from the sugar in molasses, are suspendedin water and decomposed into sugar and calcium orstrontium carbonate, as the case may be, by the action,of carbonic acid gas.

Other such processes havo been devised, but that


involving the use of strontium hydroxide is mostlargely employed.

COLD STORAGE.A valuable by-product of the beet sugar industry

is trimethylamin e, which is obtained by distillationfrom the final residue or vinasses of the Osmoseprocess, and also in large quantities from herring-brineby distillation with lime. It is a gas at ordinarytemperatures condensing in the cold to a liquidwhich boils at 3.5 deg. Cent., and is used, as we havenoticed before, in the place of ammonia, in themanufacture of potassium bicarbonate by a methodanalogous to the ammonia soda process. By heatingits hydrochloride with hydrochloric acid, methylchloride, an easily condensable gas, is obtained, andused for making certain dyes, and also as a freezing,agent in the technical production of ice.

The preservation of food by cold storage is ofgreat importance,- and depends for its usefulnessupon the availability of a large and cheap supply ofice. In the preparation of ice, advantage is takenof the heat absorption of boiling liquids. -A gasthat can easily be liquefied by pressure can be usedas a freezing agent, provided that its other propertiesare not objectionable. The gas* is liquefied bymechanical pressure, and is then allowed to evaporateunder low pressure, the only heat available for itsvaporisation being that contained by the water itis desired to freeze. The freezing agent is, of course,not destroyed, but can be recondensed and usedover again. Gases in common use as freezing agentsare methyl chloride, which liquefies at ordinarytemperature under two or three atmospheres pressure,and boils under ordinary pressure at 24 Centigradedegrees below zero, ammonia gas, which liquefiesunder about six or seven atmospheres and boils underordinary pressure at 33.5 Centigrade degrees below zero,carbonic acid gas, and cymogene (referred to inChapter V.).


CHAPTER XV.

BREWING.

THE production of malted liquors was one of thefirst industries to recognise the value of scientificinvestigation in the elucidation of technological pro-blems ; but the industry has not alone profited—thefield of work has proved so rich in discovery that animportant domain of chemical science, the chemistryof fermentation, with its applications to the leather,tobacco, food and other industries, as well as to physio-logical science, has been opened up, primarily throughthe study of the principles underlying the practiceof brewing.

Alcoholic liquors were brewed from grain stuffs inEgypt as early as the 4th Dynasty (B.C. 3000 to4000), the beverages taking the place of wine incountries where the climatic conditions were un-favourable to the cultivation of the vine. Althoughthe Egyptians had vineyards in the Nile Valley, it isprobable that this restriction of area gave rise to thebrewing of grain liquors in other less favoured parts.The earliest fermented liquor known in Britain wasmead, made from honey ; the production of beerfrom barley, and of cider from apples followed in theorder indicated. All three beverages were in use inthe South of England at the time of the invasion bythe Romans, who are said to have considerablyimproved the manufacture of beer, which subse-quently became the national drink of the country.In the Middle Ages rents were sometimes paid in maltor beer, and it is not without interest to note that oneof the municipal appointments in the time of QueenElizabeth was that of the ale-taster, a post heldby the father of William Shakespeare at Stratford-on-Avon. Ale-tasters were required to examine


beer and ale to see that they were good and whole-some, and sold at proper prices. Public analystsmay now be considered to carry on these duties,the custom of appointing ale-tasters having beendiscontinued in most places since beer and alebecame excisable commodities.

In normal times about 35 million barrels of 36 gallonsare brewed per year in the United Kingdom, involvingthe consumption of 50 million bxishels of malt, over60 million pounds weight of hops, more than a millionhundredweights of specially prepared rice andmaize, and about three million hundredweights ofsugar.

The question of water supply is of great importanceto the brewer, the nature of the impurities in thewater used in mashing greatly influencing the qualityof the product. The excellence of the pale ales-pro-duced at Burton has been traced to the existence insolution of large quantities of calcium and magnesiumsulphates in the Burton well water. Stout and porterare better brewed with the softer water of London orDublin, which does not contain the sulphates abovementioned. Sometimes the water in a locality can beso modified, by the addition of the requisite substances,as to be suitable for the brewing of different classesof beer ; but the industry has been largely establishedin districts where the natural supply needs no specialtreatment.

The production of beer from barley involves threemain operations : the conversion of the grain intomalt; the preparation of an infusion of the maltcalled wort; and the fermentation of the wort bymeans of yeast. Malt is obtained by keeping barleyin a moist atmosphere until the induced germinationhas proceeded to the requisite extent determined byexamination of the grain. The product is thenheated to a temperature above £0 deg. Cent, to stopgermination. The infusion known as wort is made bymashing the finely ground malt with water, andkeeping it for some time at about 67 deg. Cent. Theresulting liquor, after straining through spent wort,is sterilised by boiling, when hops are added to impart


a bitter flavour, and to yield to the liquor certainpreservative substances. The liquor is then clearedby settling, drawn off, cooled by " coolers" andrefrigerators, and fermented by yeast.

The chief change taking place in. malting barley isthe production of an active body called diastase, whichhas the power to convert starch into sugar. Duringmalting albuminoid substances are broken down intosimpler bodies, and the starch undergoes modifica-tions, assuming a form more easily attacked by thediastase. During the mashing operation the starchis converted by the diastase into a sugar, which is fer-mentable by yeast, thereby yielding alcohol. As thefinished malt contains much more diastase than isnecessary to convert all the starch present into sugar,starch, in the form of flaked rice or flaked maize, issometimes added to the malt before mashing, thefinal result being an increased production of alcohol.When desirable the quantity of sugar in the wort canbe increased by the direct addition of invert sugaror of glucose. Invert sugar, which contains nearlyequal quantities of two fermentable sugars—dextroseand laevulose—is produced in large quantities for theuse of brewers by boiling cane sugar with dilutemineral acids, whilst glucose, containing two sugars—dextrose and maltose—is made by the hydrolyticaction of dilute mineral acids on starch, an inter-mediate product being dextrin (British gum). Ifthe action of the acid were further prolonged dextrosealone would be the main product. Brewers'glucose contains 60-70 per cent, of fermentablesugars.

By boiling, the wort is sterilised and concentrated,certain complex protein bodies are eliminated byprecipitation, diastatic action is stopped, and theflavouring and preservative materials are extractedfrom the hops which are added at this stage. Hopscontain a yellow granular powder called lupulin,which is the most valuable constituent from thebrewers' point of view. The lupulin in new hops mayamount to 15 per cent, or more, and contains resinsand bitter principles, which give a flavouring and

TO CHEMICAL ; SCIENCE 107

exert a preservative action on the beer; andcertain volatile essential oils which also improve theflavour.

By fermentation with yeast the sugars in the wortare transformed into alcohol and carbonic acid gas.The growth of yeast, when supplied with suitablefoods, and its remarkable action on certain sugars,have held the attention of scientific men for years.Liebig, in IS39, advanced the theory that yeast, anunstable nitrogenous compound, possessed the pro-perty of communicating this instability to sugars,causing them to decompose, but the living nature ofyeast was not then recognised. About thirty yearslater Liebig's views were overthrown by Pasteur aftera long controversy, and Liebig was compelled to makecertain modifications in his theory. As the result ofa series of epoch-making experiments, Pasteur cameto the conclusion that yeast was an organism capable,under certain conditions, of maintaining its life with-out the aid of atmospheric oxygen, that element beingderived from sugars, the presence of which fulfilledthe conditions. The maximum fermentative powerof yeast was therefore attained in the absence ofatmospheric oxygen. This thsory held the field until1892, when the researches of Adrian J. Brown showedit to be untenable. In 1897 Buchner demonstratedthat the living yeast cell is not necessary for fermen-tation, but that the clear liquid extracted from theyeast by heavy pressure served the purpose. Heproved conclusively that the cause of the fermentationis an enzyme, which he called zymase. Further lighthas been thrown on the problem by Arthur Harden,who separated the active liquid into two inactiveconstituents—the enzyme and the co-enzyme—which,when remixed, became once more active. Hardenhas also shown the importance of phosphates inaccelerating the change. To summarise: the living-yeast contains and reproduces an active non-livingbody which is capable of converting sugars intoalcohol and carbonic acid gas. The yeast growsat the expense of certain foods present in thewort.


Utilisation of Waste Products.—Dried yeast is usedas a cattle food, and as the source of an excellentsubstitute for meat extract. Carbonic acid gas iscompressed and used for the aeration of beer andmineral waters.


CHAPTER XVX

ALCOHOL, WINES AND SPIRITS.

ALCOHOL is one of the most important chemicalproducts. We have already referred to it as asolvent, in which capacity it is of great service to thechemist in the laboratory as well as in industrialoperations involved in the manufacture of transparentsoap, varnishes, French polish, collodion, and celluloid-It is not only as a solvent, however, that it figuresextensively in the arts and manufactures. I t is usedin the technical preparation of chloroform, iodoform,fulminates, ether, acetic acid, and many other bodies.For certain purposes—such as the production of somekinds of whiskey and brandy, and of liqueurs, and inthe manufacture of scents, fine chemicals and drugs—only alcohol of a considerable degree of purity canbe used, and the expense is correspondingly high.

Alcohol is made from the cheapest starchy materialsavailable, such as potatoes, maize, turnips, molasses.The raw material is mashed with about 5 per cent,of malt, and fermented in the usual way. Afterdistillation in a Coffey still, the spirit is diluted withwater, filtered through wood charcoal to removefusel oil and redistilled through a fractionatingcolumn. The products are separated into threegrades : first runnings, and first and second qualityspirits. The first runnings, containing about 95 percent, of alcohol with a small quantity of aldehyde,may be used for b\u*ning and in manufactures wherethe impurities give rise to no deleterious effects.The first and second qualities, which are 96 to 97 percent, in strength and contain only traces of aldehyde—tho second quality also containing a small quantityof fusel oil—are known as silent spirit, because theyafford no evidence of their source. These qualities

110 WHAT IOTDUSTRY OWES

are used for drinking purposes—liqueurs and factitiousbrandy and whiskey—and for pharmaceutical pre-parations.

Absolute alcohol, containing 99 per cent, or more ofalcohol, is obtained by dehydrating the finer spiritsby redistilling with about half their weight of quick-lime, whilst 100 per cent, alcohol may be prepared bythe addition of a small quantity of metallic sodiumto absolute alcohol and further redistillation.

The denaturing of industrial spirit—rectified spiritand first runnings—consists in adding to the alcohol,to render it undrinkable, some substance or substanceswhich cannot be profitably separated, and which havethe minimum harmful effect in the £ processesdemanding the use of such spirit. Were it not forthe fact that in most countries the Governments per-mit the sale and use of denatured or undrinkable spiritfree of duty, the high duty on such spirit wouldrender its use in ordinary manufactures prohibitivefrom the point of view of economy, and the absenceof such facilities would prove a great hindrance tothe industries concerned.

Methylated spirit is duty free, and may be usedinstead of rectified spirit—spirits of wine—in themanufacture of chloroform and varnishes, for pre-serving anatomical specimens and for many otherpurposes. It was originally made by adding about10 per cent, of methyl alcohol—wood spirit—a productof the destructive distillation of wood, which has asharp fiery flavour and contains substances dis-agree'able both to taste and smell. The presence ofwood spirit, however, has little or no effect on theindustrial uses of alcohol, from which, moreover, itcannot be profitably removed. The main use ofwood spirit, therefore, is for denaturing purposes ;but it is also employed as a solvent for resins and inthe manufacture of dyes, its characteristic componentCH3, appearing in this role as a constituent of theintermediate products methylaniline and dimethyl-aniline, bases largely used for the production of basicdyes, such as methyl violet—the colouring matter ofrecording, copying, and typewriting inks—malachite


green, and methylene blue. The processes for theextraction and purification of wood spirit, however,were in the course of time so far improved, that itspurity eventually unfitted it for use alone as a de-naturant; it is still universally used for the purpose,but with the enforced addition of other more dis-agreeable substances, such as—in the case of ordinarymethylated spirit—not less than § per cent, ofparaffin of specific gravity 0.800. For some manu-facturing purposes the paraffin is a disturbing factor,causing turbidity on mixing with water, and beingunsatisfactory in other respects. To obviate thesedisadvantages, various denatured spirits are nowmade, containing from 2 to JO per cent, of wood,spirit with a smaller quantity of other substances ofunpleasant taste, the choice being determinedaccording to the purpose for which the spirit is to beemployed. Thus, in the manufacture of transparentsoap, a spirit denatured with wood spirit, castor oiland caustic soda is useful; in making mercuryfulminate, a mixture of wood spirit with pyridinebases forms a suitable denaturant; and in makingcelluloid the spirit may be mixed with wood spirit,camphor, and benzene. Other denaturants includetoluol, xylol, wood vinegar, turpentine, animal oil,chloroform, iodoform, and ethyl bromide, accordingto the needs of the industry for which the spirit isrequired.

Wines.—The production of wines by the fermen-tation of grapes is an industry of great antiquity.Several words in Hebrew are translated in our OldTestament as wine, and we find it associated with Noah,who, when he began to be an husbandman, planteda vineyard, drank of the wine and was drunken.Fermented grape juice was a beverage of the ancientEgyptians five or six thousand years before our time.

Wine is made by allowing the juico of grapesto ferment spontaneously, the organism inducingthe change occurring plentifully in the air dust ofvino-growing countries, and speedily infecting anysugary liquor freely exposed to the air. When whitewine is the product desired, all the seeds and husks


of the grapes are carefully excluded, because it isfrom these that the colouring matter of red winesis extracted by the alcoholic liquid produced byfermentation. The seeds and husks also give upa small quantity of tannin, which acts favourablyas a preservative of the red wines, and preventsropiness. Sparkling wines, such as champagne, aremade by dissolving sugar in a still wine and allowingit to undergo secondary fermentation in the bottle.Ordinarily, wine consists of a mixture of alcoholand water, containing from 7 to 17 per cent, of theformer, together with smaller quantities of sugar,bitartrate of potash, glycerine, and other bodies,including traces of flavouring matters. If a sugarsolution contains much more than 30 per cent, of itsweight of sugar it cannot be fermented by yeast.A solution of alcohol of 16-17 per cent, strengthalso inhibits the action of yeast, and it follows,therefore, that fermented liquor cannot contain morethan this percentage. Should a wine of greaterstrength be desired, it can be obtained only by theaddition of stronger distilled spirit. Thus thestrongest port wine, as produced by the ordinaryfermentation, contains not more than 16 to 17 percent, of alcohol, but it can be " fortified " if necessaryby the addition of absolute alcohol or rectified spiritin the proper proportion. For this purpose it isdesirable to use the strongest alcohol obtainable,as if a weaker, e.g., less than 90 per cent., were used,the water necessarily added with it would dilutethe other ingredients of the wine to an abnormalextent, and modify unfavourably its originalcharacteristics.

Spirits may be divided roughly into two classes, (1)pot-still spirits, including brandy and whiskey ; and (2)gin spirits, made by the suitable treatment of plainrectified spirit or alcohol. The manufacture ofspirits was made possible only by the discoveryof the process of distillation, and is not, therefore,of such antiquity as the wine and beer industries.The products differ from fermented liquors from whichthey are produced, mainly in the larger content of


alcohol, in the absence of non-volatile matter, andin the possession of certain distinct flavouring matters,either occurring naturally or added purposely.Cognac brandy is made by distilling from a potthe fermented juice of a small variety of grape,the alcohol passing over among the first productsof the distillation. The spirit contains about 50 percent, of alcohol, and owes its aroma and flavourto small quantities of capric (cenanthic) ester derivedfrom the wine. The colour of genuine old brandyis dixe to colouring matter extracted from the woodof the casks in which it is stored, its astringentflavour being due to tannin from the same source.New brandy is coloured to resemble the old by theaddition of caramel (sugar—generally starch sugar—•heated jbo about 190 deg. Cent.), astringency beingsometimes imparted by an infusion of tea.

Whiskey is made from malted barley, or froma mixture of unmalted and malted grain, the mixturebeing dried over a peat fire, from which the whiskeyderives its smoky flavour. By a washing operationsimilar to that practised by brewers, a wort is producedwhich is cooled quickly by refrigerators and fermentedby purified brewers' yeast, as completely as possible,at a low temperature. These eonditioBts^coEttbineto ensure the production of a good liquor free fromsourness, and with the minimum of wasteful andobjectionable impurities such as fusel oil andaldehyde. When the fermentation stops, the liquoris distilled from a large copper still—up to 12,000gallons—sometimes with the addition of soap toprevent undue frothing until all the alcohol haspassed over. The distillate from this operationknown as " low wines " is poor in alcohol and requiresa second distillation. The residue remaining inthe still contains a small quantity of lactic acid,which is often recovered and used as a substitutefor acetic and tartaric acids in processes where aweak acid is required, and where the chemical natureof the acid is not of first importance. The seconddistillate is collected in three fractions called " fore-shoots,'1 <e clean spirits," and " feints." The clean


spirit is a strong whiskey containing about 60 percent, of alcohol. It is generally diluted with waterto about 40 per cent, before being sold to the customer,the minimum being fixed by Act of Parliament (1879)at 37 per cent, by weight. The fore-shoots arehighly impure, containing fatty acids and othersubstances, while the " feints" consist chiefly offusel oil, a mixture of higher boiling alcohols, usedin recent years as a raw material in the productionof synthetic rubber, and also as a solvent. Thecc spent lees" remaining in the still is a waste forwhich as yet no useful application has been found.

British brandy and whiskey prepared in a similarway from potato starch need to be freed from a ratherlarger percentage of fusel oil than does barley spirit.

Rum, which is made by fermenting treacle ormolasses, and twice distilling the product, owes itsflavour to formic and butyric esters, and is colouredeither by ageing in wood, or artificially by means ofcaramel.

The plain spirit, i.e., a mixture containing waterand alcohol only, which is used to make gin andliqueurs, is produced by fermenting a mixture ofmalted and unmalted grain, and distilling the resultingalcoholic liquor or " wash " through a special fraction-ating apparatus such as the Coffey still. Whendistillation takes place from a pot-still little fraction-ation occurs, and a large proportion of the lowerand higher boiling substances pass over with thealcohol, necessitating a second distillation; but bythe use of a contrivance such as the Coffey still,which is too complicated for description here, thegreater proportion of the impurities can be eliminatedby one distillation.

Gin. is made by adding some substance, such asjuniper or liquorice root, to the spirit, and re-dis-tilling from a pot, when the distillate passing overcarries with it the flavouring matter extractedfrom the root. Liqueurs are made by dissolvinglarge quantities of sugar in the alcohol with variousflavouring and colouring materials.


CHAPTER XVII.

TOBACCO, INKS, PENCILS, &c.

TOBACCO is cultivated in many countries, especiallyin Virginia and the Southern States, in Mexico,Cuba, and the West Indies, in Asia Minor and Persia,in India, China, and Borneo, and in South Africa,and affords scope for the botanist, biologist, andchemist, both in the plantations and in the factories.In the days of Columbus the natives of the WestIndies smoked the rolled leaf, the Mexicans andNorth American Indians used pipes, and the Aztecsand Hispaniolan Indians applied forked tubes tothe nostrils. Tobacco was introduced into Europeby Hermandez do Toledo in 1559, into England bySir John Hawkins in 1565, and its use speedilybecame very general in spite of all forms of opposition.Smoking was the butt of the wits, denounced bythe clergy, and condemned by rulers and popes,offenders being subject to severe punishment. InTurkey it was a capital offence, and in the cantonof Berne was prohibited as an addition to the deca-logue. In England King James I. issued a " Counter -blaste to Tobacco," in which smoking was describedas " a custom loathsome to the eye, hateful to thenose, harmful to the brains, dangerous to the lungs". . . as " resembling the horrible smoke of the pitthat is bottomless ; " but although often the subjectof violent diatribes, it remains at the present daya most popular luxury among both rich and poor,and we may contrast the views of the Stnart Kingwith those of Kingsley indicated in " Westward Ho I "" When all things wore made none was made betterthan Tobacco ; to be a lone man's Companion., abachelor's Friend, a hungry man's Food, a sad man's

T


Cordial, a wakeful man's Sleep, a chilly man's Fire.There's no herb like it under the canopy of Heaven."

Tobacco is rarely prescribed in medicine oromployed in pharmacy ; but it is well known thatsmoking in moderation acts as a sedative, and is oftenbeneficial in promoting expectoration in cases ofasthma. Snuff, which is prepared from the ribsand stems of the tobacco leaf, is occasionally recom-mended to excite the secretion of mucus from thenasal membrane. The absorption of very smallquantities of nicotine is stimulating to mind andbody, but in excess the effect is depressing, narcotic,and injurious to the sight. Much depends uponthe constitution of the smoker, habituation, and othercircumstances. But we have digressed from ourobject. The industry is an important one from thefinancial standpoint. In normal times we spendbetween four and five million pounds on importedtobacco—more than twice the expenditure on dyes—and the smoker pays very heavily to the Exchequer forhis luxury. He is protected, however, by theinspection of imported tobacco by the Governmentlaboratory. Many thousand samples are examinedannually, in accordance with the legislation for-bidding adulteration or excess of moisture, offendersbeing liable to heavy penalties. Tobacco was formerlymuch adulterated with leaves of rhubarb, cabbage,dock and the like, as well as with sugar, starch,and gum; but although sweetening matters suchas sugar, treacle, liquorice, and glycerine are occasion-ally present in imported tobacco, adulterants arenow comparatively rarely detected.

The chemical composition of tobacco is highlycomplex, the determinable constituents numberingover twenty. The quality of the leaf is attributedto the nature of the soil where it is grown, though thofinished product must remain largely a matter of taste.The methods of manufacture depend on the varietyof tobacco and the purpose for which it is intended;and the processes are supervised more and moreby men of science who can render useful assistancein many ways, such as the prevention of mouldinesa


and the utilisation of waste. The leaves, whenharvested, are allowed to wither to a certain extent,and then undergo shed-drying or sweating in moderateheaps covered with matting. The leaf cells transpirecarbohydrates, albuminoid matters become con-verted into amides, and the heat generated effectsthe drying of the leaves, which then undergo fermenta-tion in bundles arranged in large heaps. Tons oftobacco are thus allowed to decompose rapidly ata temperature usually kept below 50 dog. Cent.,the bundles being turned about so that all are equallyaffected. Suchsland is stated to have preparedcultures of the bacteria of the fermentation, and tohave transferred them from fine West Indian toGerman tobacco in the course of fermentation,with remarkable improvement to the latter.

The leaf as imported to this country is subjectedto secondary fermentation after the addition of5 to 25 per cent, of water, and is dried or stoved onheated open trays, or in closed ovens subjectedsometimes to injections of steam, different methodsof treatment affecting the flavour of the product.The content of nicotine in the leaf varies from 1 to5, though it is sometimes as high as 8 per ceat.; asingle cigar often contains a deadly dose, but it retreatsfrom the heat as the tobacco burns and accumulatesin the stump or butt. By passing a current of steamthrough a mixture of lime and tobacco dust, neutralis-ing the resulting liquid with sulphuric acid, and addingcaustic potash, nicotine is liberated and may bedissolved in ether, the solution yielding almostpure alkaloid, which is employed in the manufactureof insecticides for horticultural purposes.

We propose now to deal with a few industries underscientific control which employ chemical products,and relate to commodities in everyday use.

Inks.—In early times the thoughts and actions ofmen were incised on stone, impressed on clay or wax,or carved on ivory, metal or wood ; but with theintroduction of papyrus, which we have mentioned in


the chapter on cellulose, characters were formed by theapplication of coloured fluids by means of a brush orreed. The word " ink " is associated more closelywith the more ancient methods, being derived fromthe Greek encaustos (burnt in), and from the Latinencaustum (the purple-red ink used by the laterRoman Emperors). The oldest writing materialappears to have been composed of very finely dividedcarbon in a solution of an adhesive substance, whichheld the carbon in suspension and fixed it to thepapyrus. Ink of this sort has been found on ancientEgyptian papyri, and was no doubt also in use inChina at least as early. Carbon inks are permanentand very resistant to chemical action, but there is atendency for the pigment to sink in the liquid unlessit is frequently stirred. Printing inks also consistmainly of carbon with well-boiled drying oils and soapor resinous matter. For ordinary writing purposes,however, carbon inks were superseded centuries agoby iron-tannin inks, prepared from a decoction ofgalls with copperas and gum arabic, formerly homemade, but now produced in common with many otherdomestic requirements on an industrial scale. Theaction of the tannin—from tho decoction of galls—onthe copperas produced a precipitate, which, beinginsoluble, formed a deposit, but manufacturersavoided these conditions by excluding air to preventoxidation, and by adding soluble colouring matter.Good writing ink should remain sweet and fluid whenexposed to air, should be permanent to light underordinary atmospheric conditions, and not contain anexcess of free acid which would injure the pen andpaper, though the ink is not always to be blamed forthese contingencies. In the middle of the eighteenthcentury logwood was added ; in many cases it replacedthe tannin entirely, and still forms the basis of someinks. Coloured inks have also been prepared withcochineal and indigo, and with the introduction ofcoal tar dyes a large variety of easily running inks,specially suitable for stylographic and fountain pens,have been rendered available, though it should beremarked that they are not regarded as so permanent


as the iron-gallo-tannates. Many typewriter ribbonsare prepared with coal tar dyes, and are therefore opento this objection, the ink being fairly easily removed bychemical means. Inks highly sensitive to tamperingare employed for bankers' cheques, and the detectionof forgeries often depends on the effects produced bytreatment with various chemical reagents. Copyinginks are concentrated writing solutions, usually con-taining two or three times the amount of colouringand thickening matter. It is probably no news toengineers that James Watt invented the copyingpress, the patent for which was granted to him in 1780.He employed an ink prepared from a decoction ofAleppo galls, green copperas and gum arabic, whichis much the same as the inks now used for the samepurpose, except that they contain soluble dyes,dextrin or sugar, and in some cases glycerine. Irontannin inks, when exposed to the air, become oxidisedand insoluble, so that they cannot be copied.

The juices of various plants have long been utilisedas marking inks, such plants including the ink plantof New Granada and New Zealand, the cashew nut, theIndian marking nut and others. Modern markinginks, which should withstand the action of soap andalkaline and acid liquids, mainly consist of solutionsof silver nitrate coloured with lampblack and thick-ened with gum. Salts of gold, platinum, manganese,and of other metals have been used for the same ?purpose.

Pencils.—We have already noted the use of thebrush for applying characters to papyrus. The word" pencil " is derived from the Latin penicillus, a smalltail. The use of charcoal and similar materials followedand, at an early date, metallic lead was employed tomark parchment and papers; hence, the term" blacklead" as applied to pencils, denoted theblacker mark of graphite or plumbago. As a matterof fact, the graphite used for making pencils consistsalmost entirely of carbon and contains no lead.It has been employed for this purpose since theseventeenth century, and for a long time was obtainedalmost exclusively from the Borrowdale mines in


Cumberland, being mined in compact grey-blackmasses, cut into thin plates, then into rectangularsticks and cased in wood. The mine was guardedby an armed force, and, to maintain the monopoly,an Act was passed restricting the working to onlysix weeks in the year ; for the remainder it wasflooded to prevent theft. The best quality wasexhausted early in the nineteenth century, and thepencil manufacturers turned their attention toutilising accumulations of waste from cuttings ofthe original masses, which were crushed and mixedwith other materials.

One of the results of such experiments was theintroduction of varying degrees of hardness in whichrespect the native graphite was never uniform.Conte, of Paris, is credited with the method nowgenerally employed, of making pencils from finelyground graphite mixed with varying proportions ofclay, allowing for fourteen degrees of hardness andsoftness ranging from 6 H to 6 B with HB (hardand black), and F (firm) as the middle degrees.

Graphite has since been found in many parts ofthe world. The crystalline variety occurs in Ceylon,but is not sufficiently black for pencil-making;the massive, which occurs in Bohemia, Bavaria,and Mexico, is much blacker. It is ground veryfine, mixed with water, and passed through tanksto allow the heavier particles to fall, the finer particlespassing on to five or six successive tanks, when thenecessary degree of fineness having been obtained,it is mixed with suitable clay which has been washedin the same manner. The mixture is submittedto further grinding, squeezed in bags to removesuperfluous water and forced through tubes toproduce strips of the required shapes and sizes, which,when dried and baked, are ready for casing in wood.

The wood mostly used for making pencils is thatof red cedar, not the cedar of Lebanon, but theJuniperus Virginiana which grows in Florida,Alabama, and Tennessee, and lends itself well tothe purpose on account of its soft character andstraightness of grain. It is usually cut into short thin


slats of the length of a pencil, though sometimes ofseveral lengths, and sufficiently wide for makingfrom two to six pencils. The slats are grooved toreceive the lead and, when glued together, can becut into the corresponding number of pencils, whichare then smoothed by machinery, polished, stampedwith the letters indicating the degree of hardness,and the makers' name, tied into bundles, and generallyprepared for sale. Coloured pencils are made fromspecial clay finely ground with colour, such as Prussianblue, or vermilion, and mixed with a binding material,pressed into sticks which are toughened by boilingin a mixture of special fats and waxes before they areplaced in the slats. For copying-ink and indeliblepencils, an aniline dye is used, the colour beingsoluble in water in order that impressions may betaken on tissue paper. With the demand for pencilssteadily increasing and the supply of suitable cedarbecoming quickly exhausted, manufacturers will beobliged to use other woods, or users must be contentwith mechanical pencils. The industry is restrictedto comparatively few firms, the majority being oflong standing. Details of manufacture. are largelykept secret, but enough has been said to indicate thatthe industry owes much to chemical science, in thoselection, mixing, and general treatment of materials,and to mechanical science in the invention of labour-saving machinery for the processes involved.

Other domestic requirements, such as blacklead(stove polish), and blacking, for leather, are now pro-duced under scientific control. Black lead for produc-ing a polished black surface on iron is made from themassive graphite. Blacking is made of a variety ofmaterials and consists essentially of some black pig-ment, such as animal charcoal (bone black), incorporatedwith substances capable of taking a polish by friction.A mixture of bone black, sperm oil, molasses andvinegar forms a typical blacking, while other landscontain starch as ground material with tannate ofiron as colouring agent, and gum arabic as a bindingmaterial.


CHAPTER XVIII.

GASES.

IN the article on coal, we gave a brief descriptionof the manufacture and purification of one of itsprincipal decomposition products—coal gas. Beforedrawing our work to a conclusion, we propose to saysomething of other gases, little known to those whodo not use them, and far simpler in their constitutionthan coal gas. Discovered by science, their manu-facture is the outcome of scientific investigation, andnot the mere retorting of a complex naturallyoccurring substance.

The word gas is said to have been introduced bythe Flemish chemist, Van Helmont—sixteenth cen-tury—being associated with the Dutch geest, & spiritor ghost, Danish and German, geist, from the sameroot as the Anglo-Saxon gaestlic, ghastly. To themediaeval mind, the air was a mystery, somethingsupernatural: it could not be seen or smelled, butcould be felt and heard. Gradually the idea of thematerial nature of the air was developed by theschools, but owing to the vague nature of the entityconcerned and the difficulty of handling it, littleprogress was made with experimental investigationuntil the middle of the seventeenth century. Novariety was recognised and everything of the natureof air was classed as air, until the advent of methodicalexperiment and logical deduction laid the foundationsof this fundamental department of knowledge.

A gas is physically the simplest form of matter ; thelaws governing its behaviour are less complex than thoseregulating the conduct of solids and liquids. To therecognition of this fact and the application of theprinciple of defeating the weakest enemy first, science


owes many of its most wonderful advances, such, forinstance, as we find in the application of the laws ofgases to substances in dilute solution. The extremefluid elasticity of gases and vapours and their highco-efficient of thermal expansion render theminvaluable to the engineer. The nature of explosion,the problems encountered in aeronautics, in meteoro-logy, in the study of acoustics, are all closely connectedwith the properties, both statical and dynamical, ofsubstances in the gaseous state.

Until the middle of the seventeenth century, thephilosophers—students of nature—affected to despiseexperiment, their opinions being based on observation.The alchemists—seekers after the universal solvent,the philosopher's stone and the elixir of life—loversas they were of theory and mysticism, extolled theexperimental method by which they hoped to securewealth and the extension of life. Modern experi-mental science may be considered as the outcome ofone of the controversies between two factions of theformer, combined with the overthrow of the methodsof the latter. A discussion arose between the plenists,or Cartesians, who denied the possibility of a vacuum,and the Vacuists,who maintained that there was noreason why a vacuum should not exist. RobertBoyle, born in 1626, " son of the Earl of Cork, andthe father of modern chemistry," flourished at thetime of the plenist controversy, and the problemattracted him to physical science, especially thestudy of the properties of air. In 1658 he constructedthe pneumatical machine—air pump—which wasdestined to be of primary importance in many ofhis subsequent experiments. His original aim beingto obtain a vacuum, he made with its aid somesignificant discoveries. He demonstrated air pressure,and elucidated the volume pressure relations of gases.His law—viz., that, at a constant temperature, thevolume of a given quantity of gas varies inversely asthe pressure—was rediscovered independently a fewyears later by Marriotte, a Frenchman. Boyle'sspeculations on the chemical nature of air, founded onmany observations, including the gain in weight of


metals on calcination, contributed to the advance ofknowledge in his time, but the difficulty of pioneerwork on an invisible and almost intangible mediumlimited such observations to the phenomena ofcombustion and respiration. In 1661 appeared,anonymously, " The Sceptical Chemist," a book whichcriticised the teaching of the alchemists and depre-cated their method of expression and the ambiguityof their doctrines. As the author of this productionBoyle did much to sweep away the cobwebs ofmysticism. He was an early member of the" Invisible College," a body much attacked in itsinfancy for encouraging the investigation of Nature—then regarded by many as rank heresy—whicheventually became our premier learned society, theRoyal Society of London. His researches weremainly on " air," and there is little doubt that heprepared the gases now known as hydrogen, carbondioxide, and hydrogen chloride; but he did notobserve their characteristic properties. His work,however, marked the beginning of a new era innatural philosophy, his doctrine showing that scientificadvances were made not by theory or practice alone,but by the application of both.

The discoveries and teachings of a genius have notinfrequently been overshadowed by those of a greater,and better-known contemporary. This was the casewith John Mayow, a medical practitioner of Bath,who, in his experiments on air and his deductionstherefrom, was ahead of the workers of his time- Herecognised the existence of different kinds of gase3 inthe air, and prepared a gas—nitric oxide—by theaction of nitric acid on iron. He observed its actionon air, but failed to see the analytical possibilities ofthe discovery. Boyle and Newton held the field innatural philosophy, and Mayow received littleattention. Stephen Hales (1677-1761) prepared aarge number of gases, but regarded them all as

modifications of air, and failed to make us© of thefacts he accumulated. When, however, JosephBlack (1728-1799) discovered carbon dioxide, andDaniel Rutherford (1749-1819) isolated nitrogen, both


realised that these gases were distinct in their naturefrom air.

Then followed the epoch-making discovery ofoxygen by Joseph Priestley and Carl WilhelmScheele, a Swedish chemist, working independently.Priestley also invented the eudiometer. HenryCavendish (1731-1810) made the first analysis of air,devised the electric spark method of combiningnitrogen and oxygen, thus laying the foundation ofa very modern industry, and determined the com-position of nitric acid. Cavendish proved thecompound nature of water; determined its quanti-titative composition, and also examined thoroughlythe fixed air—carbon dioxide—of Black.

All these eighteenth century investigators expressedtheir views on the action of air and combustion interms of the phlogistic theory of Becher and Stahl,and it remained for Antoine-Laurent Lavoisier, theFrench savant, who fell a victim to the guillotine in1794, to free them from this incubus and to developthe new theory wherein oxygen was assigned itsproper role as a constituent of air and a supporter ofcombustion.

Thus the composition of air—as a mixture of oxygenand nitrogen with small quantities of carbon dioxideand water vapour—and the explanation of the natureof combustion were gradually established. To theseearly workers, and especially to Priestley, Cavendish,and Lavoisier, chemical science and industry owe anirredeemable debt. Out of chaos they producedorder, and paved the way for the work of Avogadro,Clark Maxwell, and Clausius. No new essentialconstituents of air were discovered until the lastdecade of the nineteenth century, when Rayleigh andRamsay, as an outcome of the measurements, by theformer, of the density of nitrogen from various sources,including atmospheric, discovered five new chemicallyinert gases—Argon (without energy), Neon (new),Helium (Sun), Krypton (hidden), and Xenon(stranger)—no compounds containing these elementsbeing as yet known.

Hydrogen,—The discovery of hydrogen is usually


attributed to Paracelsus, a Swiss physician andchemist—fifteenth to sixteenth century. Its ex-plosive properties were known to Lemery about 1700,but it was not until seventy or eighty years laterthat Cavendish demonstrated the individualityof the gas, and showed its relation to water. I t isprepared in the laboratory by the action of a metalsuch as zinc or iron on dilute sulphuric acid, this being,in fact, the method by which it was first discovered,and it is obtained in a much purer state, when neces-sary, by the electrolysis of barium, hydroxide. Tracesof oxygen are removed by passage over hot coppershavings or platinised asbestos, the issuing gas beingdried by means of calcium chloride, or of phosphoruspentoxide.

The properties of hydrogen bear no resemblanceto those of any other element. It is colourless,odourless, tasteless, specifically lighter than any otherknown substance, very sparingly soluble in water, andcapable of forming explosive mixtures with air oroxygen, with chlorine and fluorine. It has alsothe property, in the presence of finely-dividedmetallic nickel, of combining with certain bodiesthat are chemically unsaturated. Its density isless than one-fourteenth that of air, and its lightnessand buoyancy render it of great value for use inairships and balloons. Provided that it is sufficientlypure, the two main advantages over coal gas for thispurpose are superior lifting power and the absenceof deleterious effect on the material of the envelope.

As a constituent of ammonia, hydrogen has inrecent years been largely used in Germany in a processfor the fixation of nitrogen, whereby the combinationof the two gases, under high pressure—up to 200atmospheres—at a temperature of 500 deg. Cent.,is effected by the action of certain catalytic agents,such as osmium, uranium, iron, manganese, ortungsten. The efficiency of the catalysts is enhancedby certain compounds of the alkali or alkaline earthmetals ; but catalyst cc poisons " also exist, and theseare many and various. The gases must be freedfrom these substances, the most obnoxious of which


are compounds of sulphur and the hydrides of arsenicand phosphorus. The ammonia is separated byliquefaction, produced by strong cooling, or, incertain cases, by solution in water. This processwas devised by Haber, is worked by the BadischeAnilin und Soda Fabrik, and promises to becomeone of the chief methods of producing nitrogen. Itneed not stop at this stage, however, for through thework of Ostwald a mixture of air and ammonia gas,under proper conditions, with platinum, as catalyst,yields nitric acid, and the process may be developedby proper regulation to yield ammonium nitrate, asubstance of high value as a fertiliser.

The third important use of hydrogen is, as we haveobserved in a previous article, in the hardening offats, by direct action in the presence of finely-dividedmetallic nickel. According to the method of Sabatierand Senderens certain fine chemicals are now made bythe nickel method of hydrogenation, and this alsois likely to find extended application in industry.

With these developments it has become necessaryto find means of producing hydrogen in large quan-tities at low cost. Owing to the expense of. rawmaterials, and the difficulty of securing a convenientcycle of operations whereby the starting materialsmay be recovered, production by the action of metalson acids is not to much extent carried out on theworks scale, though the method may occasionallybe used for military purposes. Many patents havebeen taken out for the manufacture, and we willrefer to some of the more important of them:—(1) By the action of steam on red hot iron, ironoxide is formed, and hydrogen is set free. It isthen purified from dust, sulphur compounds, carbondioxide, &c, by suitable scrubbing treatment.The iron oxide is reduced when necessary by replacingthe current of steam by one of water-gas, the residuefrom this reaction being a source of nitrogen—Messerschmitt process. (2) By freeing water-gasfrom carbon dioxide, by means of lime or causticsoda, and subjecting the residue to the extreme coldproduced by boiling liquid air, nitrogen and carbon


monoxide are liquefied, leaving the hydrogen in th©gaseous state—Linde-Frank-Qaro process. (3) Bythe electrolysis of the chloride or hydroxide of analkali. (4) The decomposition of acetylene—preparedfrom calcium carbide and water—by heatingelectrically. Hydrogen is prepared for Zeppelinsby this method, which yields also a valuable by-product in the form of fine lampblack. (5) The gasis also produced by a number of other patent methods,mainly useful for military purposes. Hydrolith iscalcium hydride, prepared by the action of hydrogenon calcium hi the electric furnace, and on contactwith water yields double the volume of hydrogenoriginally expended in preparing it. Hydrogeniteis a mixture of five parts of ferrosilicon, four parts ofslaked lime, and twelve parts" of caustic soda. Whenheated locally a reaction takes place, and spreadsthroughout the mass with evolution of hydrogen.Both of these processes.are due to Jaubert." Oxygen, discovered by Priestley and Scheele, and

named by Lavoisier, occupies about one-fifth ofthe volume of the atmosphere, and its properties asa supporter of life and combustion render it one ofthe most important of the elements. It is also themost abundant, representing about half the weightof the solid crust of the earth, and roughly eight-ninths of the water. It can be prepared in the labora-tory by heating chlorate of potash either alone orwith manganese dioxide, by the action of sulphuricacid on bichromates or permanganates, or by theelectrolysis of dilute sulphuric acid, or of solutionsof alkalies. On a commercial scale, Brin's.process ofheating barium monoxide—the analogue of lime—in dry, purified air to about 700 deg. Cent, under10 lb. pressure, for long held the field. The oxide

-takes up oxygen, forming barium peroxide ; thetjitrogen is then pumped off, pressure being reducedto about 2 lb. Under these conditions the peroxidegives up its excess of oxygen, which in turn is pumpedoff and compressed into cylinders, reforming themonoxide, which is available again for the same cycleof changes. The method, however, has now been


largely replaced by the liquid air process, whichdepends for its utility on tlie ease with which air canbe liquefied by the method of self-intensive coolingintroduced on the Continent by Linde and intoEngland by Hampson. Advantage is taken of thefact that a compressed gas cools on expansion. Airis compressed through a spiral, and allowed to escapefrom a jot. On issuing it is cooled, and in turncools the air in the spiral by external contact. Thusthe issuing gas becomes increasingly colder, untilfinally it issues from the jet in the liquid form. Liquidoxygen and liquid nitrogen boil at different tempera-tures, so that if the liquid air is fractionated the twogases can be obtained in a fair state of purity.

Oxygen finds application in medicine, in thechemical laboratory, and in the production of hightemperatures, such as are obtained by feeding'acetylene, hydrogen, and coal gas flames with thegas. Oxy-acetylene cutting and welding, oxy-hydrogen melting, including platinum working, theautogenous soldering of lead, and the use of lime-light, all depend on the production of an intensely hotoxygen-fed flame.

Ozone is a colourless gas, condensable in liquid airto a deep blue unstable liquid. Van Marum, in 1785,and Schonbein, in 1840, observed a peculiar smellin the neighbourhood of electrical machines inmotion, and the latter found that it was due to agas, which he named and found other means ofproducing. Andrews, in 1856, showed that thegas contained oxygen only, and Soret, in 1866, provedits composition, which is represented by the formulaO8. It is prepared by the action of a silent electricdischarge on air or oxygen, a current of which ispassed through a special apparatus called an ozoniser.The first of these was devised by Siemens in 1857,and since that date numerous patents, foundedmuch on the same principle, have been recorded.

The commercial preparation resembles that onthe small scale. The pure substance is not obtainedin either case; not more than 25 per cent, of theoxygen if? transformed into ozone under the best


conditions. The product is used in the sterilisationof water and to a less extent of certain foods.

Acetylene was discovered in 1836 by Edmund Davy,Professor at the Royal Dublin Society, during anattempt to isolate potassium by heating calcinedtartar with carbon. He obtained a black mass,which in contact with water gave rise to an inflam-mable gas, and he suggested that if a cheap methodcould be found for preparing it, the gas might wellbe used as an illuminant. Its development as anindustrial commodity was not realised until over fiftyyears later, but in the meantime several famousnames came into the literature of the subject, includ-ing Hare, Berthelot, Wohler, Kekule, Vohl, and SirJames Dewar. Hare unknowingly made calciumcarbide, and from it acetylene, by the action ofwater. Berthelot prepared metallic acetylides, andproduced acetylene electrically from methane andalso from carbon and hydrogen. Wohler madecalcium carbide by heating an alloy of zinc andcalcium to a high temperature with carbon. Kekul6prepared acetylene by the electrolysis of the salts ofdibasic unsaturated organic acids. Vohl obtainedthe gas by passing oils through red hot tubes, therebylaying the foundation of our modern oil-crackingprocesses. From American petroleum he obtaineda gas containing 20 per cent, of acetylene. Dewarobtained acetylene by passing hydrogen throughtubes made of retort carbon heated to whiteness bymeans of an electric current.

Acetylene is used, as we have already mentioned,in one of the processes for making hydrogen ; asan illuminant in isolated dwellings, and v^ motorand bicycle lamps. I t is invariably prepared bythe action of water on calcium carbide, which comeson the market in the form of grey lumps, the productof heating lime with carbon in the electric furnace.The gas owes its position as an industrial product tothe development of the electric furnace by Siemens,Bradbury, Cowles, and Moissan; but the creditfor the realisation of the possibility of producingcalcium carbide on a, commercial sgale belongs to


Willson, an American. In 1S8G, Cowles introduceda furnace lining consisting of a mixture of lime andcarbon, and produced calcium carbide by the acci-dental overheating of this lining. No attempt wasthen made to utilise the discovery ; but, in 1892,Willson,' while working at Spray, with the objectof reducing lime to obtain calcium for the reductionof alumina, prepared large quantities of the carbide,and, realising the potentialities of the substance, setup a works for its production.

Nitrogen, which forms about four-fifths of the air,is produced by the methods we' have already indi-cated,* especially the Linde-Hampson process, a«p.dis used in the synthetic preparation of ammonia, andof cyanamide and cyanides, from calcium andbarium carbides respectively.

Chlorine, discovered by Scheele in 1774, and pro-nounced an element by Davy in 1810, is a heavyyellow poisonous gas of an extremely irritatingodour. It is largely used in the sterilisation of waterand in gold extraction, and has been employed aspoison gas during the war. It is prepared by theaction of manganese dioxide on hydrochloric acid,the oxide being recovered by the Weldon process.It may be converted into bleaching powder, throughits absorption by lime, or liquefied by cold and pres-sure and stored in steel cylinders.

Carbon Dioxide, or carbonic acid gas, a wasteproduct of the brewery, is used for aerating beer andmineral waters, and is sometimes employed as afreezing agent. r

Carbonyl Chloride, or phosgono, prepared by theinteraction of chlorine and carbon monoxide in thepresence of animal charcoal, or of antimony penta-chloride, or by the action of fuming sulphuric" acidon carbon tetraclilorido, is used in the manufactureof dyes, and has also boon employed as a poison gas.

Laughing Gas, or nitrous oxide, is made by heatingammonium nitrate. It was discovered by Priestleyhi 1772, and is used as an anaesthetic in dentistry.

* liefer to Agricultui-e and Hydrogen.K


We do not need to dilate on. the relation betweenscience and these products which are so obviously-scientific in their conception, elucidation and deve-lopment.


CHAPTER XIX.

GOVERNMENT CHEMISTRY.

IN the article dealing with Agriculture and Food,we havo referred to the official agricultural analystsand public analysts, who are appointed under statutesto safeguard the quality of supplies of fertilisers andfeeding stuffs, food and drugs ; and we will now referto other official chemists directly or indirectlyconcerned with industry.

In 1843 a laboratory was established at SomersetHouse, in connection with the Inland RevenueDepartment, to check adulteration of tobacco, andlater a second laboratory was established at theCustom House for the examination of wines, spirits,and other imported articles liable to duty. In 1894the control of these laboratories was entrusted toone Principal, and in 1897 the Excise Branch wastransferred to a new building at Clement's Inn-passage.In 1911 the Government Laboratory was constitutedan independent department under the Treasury, witha separate Parliamentary Vote, entitled " GovernmentChemist." The Laboratory undertakes investiga-tions for every other Government Department, thegreater part being carried out at Clement's Inn-passage, and in the branch laboratory at the CustomHouse. The Government Chemist also controlseighteen stations in different parts of the UnitedKingdom, where tests are made for revenue purposes.From a recent report, wo gather that the work for theDepartment of Customs and Excise relates, mainly,to the assessment of duty and drawback, and to regula-tions and licences, in connection with the manufactureand sale of dutiable articles, such as beer, spirits,wine, tobacco, tea, sugar, coffee, cocoa, and prepara-tions advertised for the cure or relief of human


ailments—commonly called "patent medicines."The work for the Admiralty includes the examinationof food substances, the analysis of metals and ofcontract stores ; that for the Board of Agricultureand Fisheries refers largely to imported dairy produceand margarine, and includes—for the FisheriesDivision—samples of river water believed to havebeen polluted and to have caused injury to fish, aswell as the determination of the salinities of samplesof sea water for the Permanent International Councilfor Exploration of the Sea. Samples of beer andwhiskey are examined for the Central Control Board(Liquor Traffic); and of drugs, phannaceuticalsand contract supplies for the Ciown Agents for theColonies. Fire-clay and limestone from variousdistricts are examined for the Geological Survey;lead glazes and enamels for the Home-office; drugsfor the India-office, and stamps and inks tor theBoard of Inland Revenue. Investigations on pre-servatives in food are carried out for the LocalGovernment Board ; and on paper, pigments, gum,engineering and general stores for the Post-office ;ink and typewriter ribbons for the Stationery-office ;lighthouse stores for the Corporation of TrinityHouse ; lime and lemon juice and ship's stores for theBoard of Trade ; food supplies for the Army, drugsand surgical dressings, for the Army Medical Depart-ment, for the War-office ; samples of varied characterfor the War Trade Department; samples of water forthe Office of Woods and Forests ; of contractors*supplies and of water for the Offices of Works—London and Dublin; and samples referred by themagistrates under the Sa3e of Food and Drugs Acts,1875 and 1899, and submitted by the Board ofAgriculture, under the Fertilisers and Feeding StuffsAct. The total number of samples examined duringthe year ended March 31st, 1916, was 383,892. Thework has obviously an important bearing on industryand commerce, and entails the employment of alarge technical staff, of which many members arerequired to be highly trained and competent chemists.Aa illustrating the value of their work, we may refer


to the examination of food for the armie3 hi the fieldduring the war, work essential in the interests bothof th© health of the troops ar.d of ih? Exchequer.The food must be wholesome ; bur ths findings of thachemists will detemaine the cash value of the supplies:a deviation of, say, 1 or 2 per csnt. cf moisture inflour, biscuits or margarine, may involve a reductionof Iiundxeds of pounds on a single contract.

Although the Goverrjn?nt- Laboratory constantlyadvises other department.?, some possess their ow.ilaboratories for special purposes. The Admiralty hasa staff under the Admiralty Chemist, and employschemists in connection with the examination ofvarious materials of construction arid victuallingstores. The Admiralty has also its duly appointedAdviser on Petroleum, as well as officers possessingspecial scientific experience, and professors ofchemistry in the Royal Xaval Colleges. The War-office, too, makes good use of chemists in manymatters arising out of the conditions of modern war-fare, a n d instruction in chemistry is given »m theRoyal Ordnance College, the Royal Army MedicalCollege, the Royal Military Academy, and otherestablishments. Under the Ministry of Munition?,in addition to chemists engaged in an advisory capa-city, there are considerable numbers in charge of theproduction of explosives in Government and con-trolled factories, and special staffs are appointedfor research and inspection work-

Official analysts are appointed to the Home-officefor tosdcological work, as well as in connection withthe Explosives Department and the Factory Depart-ment. The Local Government Board possesses aDepartment for the inspection of food and a staff cfspecially qualified inspectors to assist in the adniinis- -tration~of the Alkali, &c, Works Regulation Act.The Metropolitan Water Board and the Rivers Boardsin various parts of the country have their chemicaland bacteriological laboratories, and so have theSewage Boards and Works. The Scottish Office alsoappoints inspectors under the Alkali Act- and RiversPollution Prevention Act.


The London County Council controls a consider-able staff for chemical investigations, including gastesting, and the Board of Trade appoints the GasReferees, in accordance with the Metropolis GasActs, to prescribe the apparatus and materialsto be employed for testing the illuminating power,calorific power, purity and pressure of the gas,the mode of testing, and, in certain cases, the timesof testing, the current prescriptions being publishedin the " Notification of Gas Referees." Other countyand borough authorities make provision for the inspec-tion of water and gas supplies. Chemists are alsoincluded in the stafi of the Patent-office, and Assayersrender responsible service in the Royal Mint andat the Assay Offices, as well as for the Bank ofEngland.

The Scientific and Technical Department of theImperial Institute conducts investigations for theIndian and Colonial Governments, chiefly relating tothe composition and utilisation of raw materials.The National Physical Laboratory includes a Depart-ment of Metallurgy and Metallurgical Chemistry.Laboratories are attached to many public Institu-tions, such as the Davy-Faraday Research Laboratoryof the Royal Institution, and those of the ListerInstitute and the Royal Dublin Society.

The existence of this extent of official organisationin chemistry is little known to the general public,but it is obviously indispensable to the well-beingof the community. The personnel of our chemicalservice includes many men of science of high reputein their professions who deserve well of their country,and it is essential that the conditions attaching tothis service should be such that it will continue toattract chemists of the highest competence. We haveendeavoured to make this list fairly-comprehensive,but have not referred to India and the OverseasDo-minions, where many chemists hold appointmentsanalogous to those we have indicated; nor have wereferred to the valuable work carried out by analystsin hospitals and public health laboratories, or theappointments held in the Universities and Technical


Colleges, to which we lock for the continued supplyof lieutenants to meet our requirements in the variousbrancb.es of chemical practice.


CONCLUSION.

WHILE we have confined our attention mainly tothe debts of industry to chemical science, wo do notsuggest that those due to physical and mechanicalscience should not be similarly acknowledged.

The art of engineering has been steadily built upthrough the ages, but modern developments are,in the main, directly attributable to the advanceof science. In chemical industries, however, theprocesses of manufacture, in many cases, precededthe discovery of the scientific principles on which theywere based. The ironmaster, the dyer, the soapand candle maker, the tanner, the potter, and theglass manufacturer, were • in existence centuriesbefore serious attention was paid to the science under-lying their work. Conventions die hard, and fora long time there was little enthusiasm to take advan-tage of what science had to offer. It is freely admittedthat the state of civilisation attained before the adventof modern science was far removed from the conditionsof life of primitive man ; but it is claimed thatwhile science was so little developed, industry hadto look to experience as the only .basis to work upon.Experience, accumulated slowly and at great cost,had done great things ; but the rate of progressin industry developed in the past century defiescomparison with all the centuries combined sincetime was—so far as we know ! Still, let us admit thatthe inheritance was great, and that even the alchemistpreserved much that was good in chemistry, justas the monks of the Middle Ages preserved muchthat wa3 good in classical literature and architecture.We have endeavoured to indicate the interdependenceof science and industry on one another, and to showhow frequently science—" the nursling of interestand the daughter of curiosity"—piu*suod for her


own sake, has sooner or later proved her practicalutility. Incidentally we have shown that though" Genius is of no country," British men of science,often in the face of small encouragement, have playedtheir part in industrial development. There isno reason to depreciate the value of their work, or topay much attention to the Jeremiahs who seem todelight in bemoaning the industrial and commercialposition of this country but are seldom able to offerany constructive criticism.

Advancement may be the outcome of the labours ofthe consultant, the chemist on the works, the officialchemist, or the professor; all have contributed theirshare to discovery and invention. In any case, it iscertain that our industries have utilised their know-ledge, skill and experience to a greater extent thanhas been generally recognised; otherwise much thathas been done in the last three years would have beenimpossible, and our position would have been far worsethan It is.

We feel that the apathy towards science prevailingbefore the war was more imaginary than real and,such as it was, is being overcome ; that the generalpublic is beginning to realise something of theimportance of science in the affairs of everyday life,and that the time is at hand when the services ofthe man of science will be better understood andconsequently more substantially rewarded. Themen of science themselves are increasing in numberand influence ; their work lies more and more in thecontrol of large scale operations, as well as in thelaboratory. The time has passed when men fearedto probe into the truth as if it were sacrilege, or toimagine things beyond certain knowledge and estab-lished fact, or to explore into realms of not only theimprobable but the seemingly impossible, whence somuch, with the aid of science, has been and is yet tobe derived.

To-day, the arts and sciences go hand in hand:the engineer and the chemist, each recognising thelimits of his own domain, though the line dividing themmay often be difficult to define, co-operate with one


another and mutually assist in the solution of indus-trial problems. Now is the time for leaders of indus-try to see to it that the opportunity is taken of makinggood, wherever possible, the connecting link betweenscience and practice. A thorough overhauling ofnet-bods and plant should keep our consultingchemists and engineers well employed in preparationfor the future. There is no lack of good men, andsoon there will be enough and to spare for permanentappointments on the works.

If in these articles we have been successful inindicating some of the triumphs of science in industry,and if our efforts have in any way conduced to a betterrealisation of the value of scientific thought andmethod, we may rest satisfied that our labour has notbeen in vain.


BIBLIOGRAPHY.

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Manufacturers. London, 1910-1911.BLOT AM", C. L. Chemistry, Inorganic and Organic.

Edited by A. G. Bloxain and S. Judd Lewis. London, 1913.BORCHERS, W. Electric Smelting and Refining. London,

1904.BORCHERS, W. Metallurgy. Translated by W. T.

Hall and C. R. Haj-ward. London and New York, 1911.BROWN, J. CA:MPBELL. History of Chemistry from the

Earliest Times to the Present Day. London, 1913. -; '-BURGESS and LE CHATEUER. The Measurement of

High Temperatures. Xew York, 1912.BUTTERFZELD, W. J. A. Chemistry in Gas Works.

Lecture, Institute of Chemistry. London, 1913.BYROM and CHRISTOPHER. Modern Coking Practice.

London, 1910.CAIN and THORPE. The Synthetic Dyestujfs and the

Intermediate Products from which they are derived. London,1917.

CHAPIMAN, A. CKASTON. Brewing. Cambridge, 1912.CROSS, C. F. Cellulose. Lecture, Institute of Chemistry.

London, 1912.CROSS and BEYAN. Researches on Cellulose, 1895/1910.

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DREAPER, W. P. The Research Chemist in the Workswith Special Reference to the Textile Industry. Lecture,Institute of Chemistry. London, 1914.

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Man. London, 1917.HARBORD and HALL. The Metallurgy of Steel. London,

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HERRICK, R. F. Denatured or Industrial Alcohol. NewYork, 1907.

HILDITCH, T. P. A Concise History of Chemistry.London, 1911.

HILL, C. A. The Function and Scope of the Chemist ina Pharmaceutical Works. Lecturo, Institute of Chemistry.London, 1913.

LAFAR, FRANZ. Technical Mycology. London, 1910.LEEDS and BUTTERFIELD. Acetylene. London, 1910.• LEWKOWITSCH, J. Chemical Technology of Oils, Fats

and Waxes London, 1913-1915.Louis, HENRY. The Dressing of Minerals. London,

1909.LTJNGE, GEORGE. Coal Tar and Ammonia. London,

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MACNAB, WILLIAM. Explosives. Lecture, Institute ofChemistry. London, 1914.

MCMILLAN, W. G. A Treatise on Electro-Metallurgy.London, 1899.

MARSHALL, ARTHUR. . Explosives. London, 1917.MELLOR, J. W. Treatise on. Quantitative Inorganic

Analysis. London, 1913. ""MEYER, ERNST VON. AT History , of- Chemistry from

Earliest Times to the Present Day. Translated by GeorgeMcGowan. London, 1906.

MIERS, Sir H. A. Mineralogy. "London, 1902.NEWLANDS, "!E>. E. R. Sugar. . London, 1913.PORRITT, B. ~t). The Qhcmislry of Rubber. London,

1913.PRICE, T. SLATER. Per-acids and their Salts. London,

1912.PROCTER, H. R. The Principles of Leather Manufacture.

London, 1903.RAMSAY, SIR WILLIAM. The Gases of the Atmosphere,

the History of their Discovery. London, 1915.• REDWOOD, Sir BOVERTON, Bart. Petroleum. London,

1913.ROBERTS-AUSTEN, Sir W. C. Introduction to the Study of

Metallurgy. London, 1910.ROSCOE (Sir H. E.) and SCIIORLEMMER. Treatise on

Chemistry. London, 1911-1913.ROSE, Sir T. KIRKE. The Metallurgy of Gold. London,

1915. .STANSFIELD, ALFRED. The Electric Furnace. New

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TERRY, HUBERT L. India-rubber and its Manufacture.London, 1907.

•THORPE, Sir EDWARD. A Dictionary of AppliedChemistry. London, 1912.

History of Chemistry. London, 1909-10.TILDEN, Sir WILLIAM A. Chemical Discovery and

Invention in the Twentieth Century. London, 1916.TROTMAN, S. R. Leather Trades Chemistry. London,

1908.TURNER, T. The Metallurgy of Iron. London, 1915.WHITE, EDMUND. Thorium. Lecture, Institute of

Chemistry. London, 1912.WOOD, JOSEPH TURNEY. The Puering, Bating, and

Drenching of Skins. London, 1912.WRIGHT, S. B. A Practical Handbook on the Distillation

of Alcohol from Farm Products, and De-naturing. NewYork, 1907.

144

o f L I B R A R Y j z

ABBE, 71Abel, 46Acetic Acid, 81Acetone, S6Acetylene, 130Acetylsalicylic Anhydride, 89Aehard, 20, 101Acheson, 67, 69Acids, 80Agriculture, 95Alcohol, 84, 109

, Absolute, 110, Denaturing of, 110

Alizarin, 43Alkali Act, 30

Manufacture, 27, Manufacture by Elec-

trolysis, 32Waste, 29

Alum-tan, 61Aluminium, 15Alundum, 69Ammonal, 47Ammonia, 37

Gas, 103Ammonia-soda Process, 31Ammoniacal Copper Soluti en,

84Ammonium Salts, S3

Sulphate, 23Anaesthetics, S5

, Local, 89Analytical Re-agents, 87Andrews, 129Aniline, 44Anthracene, 40Antifebrin, 89Antimony Salts, 84

Antipyretics, 89Antiseptics, 89Archer, 91Arsenic Acid, 81

, Organic Compounds of,S9

Aspirin, 81, 88Astatki, 55Atoxyl, 89Atropine, 88

BACON, Roger, 45Bactericidal Agents, 89Barium, Peroxide, 83

Salts, 83Bases, 81Basic Slag, 9SBeer, 104Benzene., 39Benzine, 54Benzoic Acid, 81Bernard Freres, 16Berthelot, 130Berzelius, 17Bessemer, 3Bevan, 52Bieberich Scarlet, 42, 43Birkeland and Eyde, 97Bismuth Salts, 84Black,124Blacking, 121Black Lead, 121Blast Furnaces, Water-

jacketed, 10Blasting Gelatine, 47Bleaching Powder, 30Blue Prints, 93


Boric Acid, 81Bottieher, 7SBouchardat, 64Boullay, 86Boyle,"35, 90, 123Braconnot, 45Bradbury, 130Brandy, 113Brewing, 104Brnrs Process, 12SBrown, A. J., 107Brunner, 15Brunner, Mond and Co., 32Buchner, 107Bunsen, 15Butadiene, 64Butter Substitutes, 5S

CALLEXDAR, 79Calomel, S3Calotype Process, 91Camphor, 55Candles, 57Caoutchouc, 63Carbohydrates, 48Carbolic Acid, 39Carbon Disulphide, 84Carbonic Acid Gas, 103, 108Carbon Printing Process, 93

Tetrachloride, 85Carbonyl Chloride, 131Carborundum, 69Castner, 15, 32Catalyst, Poisoning of, 26Catalytic Agents, 31Cattermole, 8Caustic Potash, 81

Soda, 28, SICavendish, 125, 126Caventou, 88Cellon, 52Celluloid, 52Cellulose, 48Cement, 65Cementation, 2, 3

| Chamois Leather, 61Chanee-Claus Method, 29

| de Chardonriet, 51j Chevreul, 56

Chloral, 8QChlorates, 33Chlorate of Potash, 30,Chlorine, 131

, Recovery of, 30, 32Chloroform, SoChrome-tan, 61Chromium, 17Cinnamoylsalicylic Anhy-

dride, 89Citric Acid, 80Clark (Water Treatment), 6Claudet, 29Claus, 29Clayton, 35Cleaning Spirit, 54Coal, 34Coal-gas, 35Coal Tar, 36Cocaine, 89Cochineal, 41Coke, 34Cold Storage, 103Colloidal State, 61Colour Photography, 93Contact Agents, 31

Process, 26Conte, 120Cookworthy, 65, 7SCopper, 10

in Pyrites, 29, Salts, 84

Cordite, 46Corrosive Sublimate, 83Cowles, 130, 131Cresylie Acid, 39Cronstedt, 14Crookes, 97Cross and Bevan, 52Cyanamide Process, 97Cyanamides, 83Cyanides, 62, 83, 97

! Cymogene, 54, 103


DAGUERRE, 90Dale, 48D'Arcet, 20Davy, Edmund, 130Davy, H., 15, 16, 25, 61, 90,

131Deacon, 31Debray, 20Delprat, 8Descotils, 20Desmond, 61Deville, 15, 17, 20Dewar, 130Diastase, 106Diffusion Process, 101, 102Disinfectants, 89Dobereiner, 71Dowson Gas, 35Drugs, 88Dry Plates, 92Dye Industry, 41Dyeing, 44Dyer and Hemming, 32Dyes, Artificial; Advantages

of, 42Dynamite, 47

EGGS, Preservation of, 83Ehrlich, 89Eitner, 62Elmore, 7, 8Elution, Process, 102Enamels, 75Epsom Salts, 83Esparto, 50Essential Oils, 55Ether, 86

, Extraction by, 12Everson, 7Explosives, 44

FATS, 53Feeding-stuffs, 98Fermentation, 107Ferrochrome, 17Ferromanganese, 3

For ro vanadium, 19Fertilisers, 95Fertilisers and Feeding Stuffs

Act, 9SFery, 79Filaments, Electric Lamp, 17Fine Chemicals, 80Firo-extinguisher, 85Fleurscheim, 47Flotation of Minerals, 7Food, 95, 99Formic Acid, SOFox Talbot, 91Fraunhofor, 71Freezing Agents, 103Fuel, Economy of, GFusel Oil, 114

GANISTER, 69Gas Carbon, 37, 69

'•, Illuminating, 34, 54Gas Light and Coke Co., 36Gasolene, 54Gay-Lussac, 25, 48Gelatine Dynamite, 47Glass, 70

, Etching of, SI, Optical, 71, Resistant, 72for Thermometers, 72

Gin, 114Glovor, 25Glucose, 106Glue, 62Glycerino, 50Gold, 19

in Pyrites, 29Salts, 84

Goodyear, 63Gossago, 30Government Chemistry, 13.*$Graham, 102Graphite, 69, 119, 120

Ores, 7Guinand, 71Guncotton, 45


Gunpowder, 45Guthrie. So

HABER/S Process.. lit>Hadfield, 5Hales, 124Hampson, 129Hancock, 63Harcourt, 71Harden, 107Hardening of Oils. 14Hare, 20, 130Harries, 64Heinzerling, 62Hemming, 32Henderson, 29Herschel, 91Heumann, 43Hides, Treatment- oi, 60Hops, 106Huntsman, 2Hydrochloric Acid, 30Hydronourie Acid, 81Hydrogen, 125Hydrogen Peroxide. S3Hydrogenite, 12SHydrolith, 128Hyoscine, 88Hyoscyamine, 8SHypo, S3Hypochlorites, 33

INDIGO, 42, Artificial, 25

Inks, 117Insecticides. S9Invert Sugar, 106Iridium, 20Iron Sulphate, 84Isoprene, 63

JACKSON. C, 86, H., 73, 74

Janetty, 20

Jaubert, 128Johnson, Mat they and Co., m2u

KAINITE, 82Kekule, 130Kerosene. 54Kestner, 24Knapp, 62Knight, 20

LACTIC Acid, 80. 113Lamp Oil, 54Lampadius, 84Laughing Gas, 83, 131Laurent, 47Lavoisier. 125Lawrence, S5Lead Azide, S4

Carbonate, 84Chamber Process, 24, Desilverisation of. 11, Purity of, 13

Leather. 59Leather Cloth. 62Leblanc, 27Le Bon, 36Le Chatelier, 4. 65. 7!)Lefevre, 24Lemery, 24, 126Liebig^ 107Lignocellulose, 50Ligroin, 54Linde? 129Linde-Frank-Caro Process.

128Lipmann, 93Liqueurs, 114Liquid Air Process. 120Lumiere, 93Lupulin, 106Lyddite. 47

MAC ARTHUR-FORREST, 19Macintosh, 63

L

148 WHAT INDUST&Y OWES

Madder, 42Magnalium, 16Magnesia, 82Magnesium, 16

Sulphate, 8frMagnetic Separation, 10Malt, 105Mantles, Gas, 18Marggraf, 101Marriott©, 123Martens, 4Mat-thews, 64Mauvoine, 44Mayow, 124McDougall and Howies, 97Melinite, 47Mercury Fulminate, 83Mosserschmitt Process, 127Metallography, 4Methyl Alcohol, 110Methyl Chloride, 103Mineral Tannages, 61Minerals, Separation of, 7Moissan, 17, 130Molybdenum, 16Monassito, 18Mond, 14, 32

Gas, 35Mordants, 44Mortar, 65Motor Spirit, 54Murdock, 35Muspratt, 27

NKOSALVARSAN, 80Nickel, 14Nicotine, 11G, 117Niepce, 90Nitrides, 97Nitrogen, 131

, Fixation of, 98Nitroglycerine, 46Nobel, 46Nordhausen, 26Novocaine, 89

OILS, Animal, 55, Hardening of, 14, Vegetable, 55

Osmium, 20Osmond, 4Osmose Process, 102Ostwald, 127Oxalic Acid, 48, 80Oxygen, 128Ozone, 129

PALLADIUM, 21Paper, 49Paracelsus, 128Paraffin Wax, 54Parker, 66Parkes, 11, 12, 13Parting of Gold, 20Pasteur, 107Pattinson, 11Pelletier, 88Pencils, 119Porcarbonates, 83Perfumes, 56Porkin, 44, 64Peroxy Compounds, 83Persulphates, 83Petrol, T>4Petroleum, Distillation of, 54Phenacetin, 89Phosgene, 131Photographic Materials, 94Photography. 90Piat, 63Picric Acid, 47Pitch, 36Platinum, 20

Salts, 84Plattner, 19Plentst Controversy, 123Plumbago, 110Poison Gasew, 131Porcelain, 77Potassium Salts, 81

Thiocarbonate, 85Pott, 78


Potter, 8Potter's Cones, 7SPottery, 77Priestley, 63, 125, 131Procter, 59, 62Puering, 60Pulvis Fubninavs, 4T>Pyrometer, 79

QUININE, 88

RAMSAY, 125Rayleigh, 125Refractory Materials. 68Reid, 46Rhigolene, 54Rhodium, 21Roberts-Austin, 4Roebuck, 24Rolland, 32Rubber, 63

, Synthetic. 04Rum, 114Rutherford, 124

SABATIER. 127Salicylic Acid, 81, SsSalipyrene, 89Salts, 82Salvarsan, 89Sauveur, 4Scheeie, 20, 90, 125, 131Scheibler, 102Schloessing, 32Schonbein, 45Schott, 71Schultz, 62Sefstrdm, 19Seguin, 61Senderens, 127Separation, Magnetic, 10Sepia, 41Shale Oil, 55Shimose, 47fiicoid, 52

Siemens, 4, 129, ISOand Halske, 20

Silica, Fused, 69. 73Silicon, 69Silk, Artificial, 48, 5 LSilver in Pyrites, 29

Salts,v 84Simmonds, 79Simpson, 85Smeaton, 65Smelling Salts, 83Soap, 56Sobrero, 46Soda Ash, 2SSodium, 15

Bicarbonate, 2S, 31Carbonate, 2SSalts, S3Peroxide, 83

Solar Oils, 55Solvay, 28, 31, 32Solvents, 84Sorby, 4Soret, 129Souberain, 85Spiegel, 3Spirits, 112Stead, 4Steel, 2Steels, Microscopic Structure

of, 4——, Special, 5Steffen, 102Stolzel, 78Stoveine, 89Strange, 64Strontium Hydroxide. 82

Salts, 83Strychnine, 88Suchsland, 117Sugar, Beet, 101Sugar, Cane, 100Sulphide Ores, Concent ration

of, 7Sulphur, Recovery of, from

Alkali Waste, 29, Chloride, S4

i. 2


Sulphuric Acid, 22, Fuming, 26, Impurities in, 87, Removal of

Arsenic from, 27Superphosphate of Lime, 9(»Swan, 62Swartz, 45

TALBOTYPE Process, 91Tar, Distillation of, 36

Fractions, 38Tartaric Acid, 80Tavener, 20Tawing, 61Tennant, 20Tetranitroaniline, 47Thermite Process, 17, 19Thomas and Gilchrist, 3Thorium, 17Thorpe, 79Tilden, 64Tin Ore, Concentration of, 7

Salts, 84T.N.T., 45Tobacco, 115Toluene, 39Tolypyrene, 89Trimethylamine, 81, 103Trinitrotoluene, 45Tungsten, 16Tyrian Purple, 41

UNVEBDORBEK,44

VALENTINE, 23Van Helmont, 122Van Marum, 129Vanadium, 19 ^"" ^"Vaseline, 54 ^ \Y^$--

Vauquelin, 17Vegetable Tannin ir, (>]Vergara, 96Veronal, 89Vieille, 46Vohl, 130Vulcanising, 63

WASHING Soda, 28Water, for Brewing, 105

Gas, 34Glass, 83

, Softening of, 0Watson, 35Watt, 119Waxes, 53, 57Wedgwood, 90Weldon, 31Weldon Process, 131Welsbach, 19Welter, 47West-Knight and Gall, 39Whiskey, 113Williams, 63Willson, 131Wines, 111Winsor, 36Wohler, 15, 17, 130Wollaston, 20Wood, 9

, Mechanical, 50Pulp, 51

, Chemical, 50Spirit, 110

Wort, 105

YOUNG, 55

-1 Sjrag -Qhioride*. 83

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