564 SCHOOL SCIENCE AND MATHEMATICS

me a convenient way of emphasizing and cataloging several im-portant chemical processes. It brings out the effect of conditionson chemical action, conditions which are extremely important andwhich we are so apt to overlook on account of our system ofchemical shorthand. It discloses one of the great problems ofchemical research, the discovery of conditions that will make areaction go to completion in the desired direction successfullyand economically, problems which we teachers must presentin such a manner that they will serve both as a challenge and in-spiration to those boys and girls whom we would recruit as thefuture leaders in our science.

A GENERAL GAS LAW APPARATUS.BY JACOB JORDAN,

Oregon Agricultural College, Corvallis.The apparatus which is described in this article is the result

of a request from one of the engineering schools of this college,that the Physics Department include an experiment on thegeneral gas law in its laboratory course.While there is nothing fundamentally new about the ap-

paratus, the writer has never seen it described or used. Thisdescription is given because of the satisfactory results obtainedin the freshman laboratory,As a first attempt an ordinary Boyle^s Law apparatus was

placed under a sheet iron cylinder closed at the top, and a heat-ing coil was placed inside of the cylinder so that the tempera-ture, volume, and pressure of the air in the Boyle^s Law tubecould be varied simultaneously. Readings of the temperatureof the confined air and of the height of mercury in each arm ofthe tube were taken simultaneously. With the temperaturecontinuously rising, a series of readings were taken and PV/Tcalculated. The results were so enocuraging that it was decidedto modify the apparatus ;jthe^accompanying photograph shows itas finally constructed.A glass U-tube about 12 inches long was sealed flat (not hemi-

spherical) at one end. A piece of a meter stick was placed be-hind the arms of the U, and the two were fastened to a widersupport. The support was then placed in a wooden box, with aglass front, of dimensions 15x6x7.5 inches. A thermometer canbe inserted in a hole in the top of the box, preferably with itsbulb about half-way between the top and bottom so that it willindicate the average temperature.

GENERAL GAS LAW APPARATUS 565

Behind the U-tube support, the heating coil is suspended byheavy copper wire leading to binding posts on the rear of the box.The coil is about 8 inches long and 1 /4 inch in diameter, and is

made of 24-gauge manganin wire.

For a large laboratory section, several of these pieces of ap-paratus, preferably of different resistances, so that the rates ofheating will be different, can conveniently be connected in serieswith a single rheostat and ammeter, to a 110V AC main. Inpractice it has been found advisable to start with a current ofabout 2.5 amperes and to increase this by steps to about 3.5amperes. Too rapid heating will cause the thermometer to in-dicate too low a temperature.Having the tube filled with dry air is of prime importance in

obtaining results that really give a constant value of R, com-

566SCHOOL SCIENCE AND MATHEMATICS

puted from PV/T, as can be seen from the accompanying tablesof data. Table A refers to a tube containing a high percentage ofmoisture, B to one containing ordinary room air, and C to onecontaining dry air. Table C was obtained with a tube that hadbeen heated and evacuated to drive off the occluded gases andfilled with air bubbled through concentrated sulphuric acid, theheating, evacuating, and filling being repeated ten times beforethe mercury was introduced. The tube referring to table B washeated and evacuated and then filled with ordinary room air.

If desired, the apparatus can easily be modified to admit ofgreater range of pressure change and of volume change. Thesmall cost of construction, the simplicity of design, and the easeof manipulation of this piece of apparatus as well as the impor-tance of the laws it illustrates should recommend it to both thehigh school and college teacher of physics.

TABLE A.Moist Air in Tube

Top of Closed Tube 36.85 cm.Barometer 76.5 cm.

12345678910

1Hg.

Closedcm.

21.7521.220.720.219.919.318.9518.5517.9517.45

2Hg.Opencm.

30.6531.231.732.2532.633.1533.6 \34.034.6 i

35.15

3t°

25.831.336.241.844.550.556.560.065.870.3

4rpo P

299.0304.0309.0315.0317.5323.5329.5333.0339.0343.0

85.486.587.588.5589.290.391.1591.9593.1594.2

15.1015?6516.1516.6516.9517.5517.9018.3018.9019.40

7PV/T

4.304.354.574.704.764.924.965.055.205.32

TABLE B.Room Air Dried by Heating and Evacuating Tube

Top of Closed Tube 59.7 cm.Barometer 76.5 cm.

Closed

123456789

iHe.

cm.43.9543.743.643.543.243.1543.042.85 �

42.35

2Hg.Opencm.45.545.845.946.046.346.546.746.847.35

31°

22.530.038.042.050.554.060.063.074.0

4rpo

295.5303.0311.0315.0323.5327.0333.0336.0347.0

78.0578.678.879.079.679.8580.280.4581.5

6V

15.7516.016.116.216.516.5516.716.9517.35

7PV/T

4.174.154.084.034.074.054.024.064.07

TEACHING PHYSICS 567

TABLE C.Air Dried by Bubbling Through H:2S04

Top of Closed Tube 98.9 cm.Barometer 75.8 cm.

123456789101112

1Hg.Closedcm.85.985.785.6585.585.3585.2585.184.9584.7584.6584.5584.35

2Hg.Opencm.89.990.0592.2590.490.590.790.991.0591.2591.491.5591.75

3t°

34.840.345.050.055.060.066.070.076.080.085.090.0

4rpo

307.8313.3318.0323.0328.0333.0339.0343.0349.0353.0358.0363.0

5P

79.880.180.480.780.9581.2581.681.982.382.5582.883.2

6V

13.013.1513.2513.413.5513.6513.813.9514.1514.2514.3514.55

7PV/T

3.383.373.353.353.3583.333.3253.3323.3353.3353.323.34

SOME PRACTICAL PROJECTS IN TEACHING PHYSICS.

BY C. F. PHIPPS,Northern Illinois State Teachers College, DeKalb, III.

Physics deals with so many things connected with our home,school and community life, that if it is presented in a practical,rather than the usual cut-and-dried way, it is both interestingand instructive to our youth. Half a century ago there werefewer inventions and up-to-date conveniences, so the people ofboth city and farm were able to become acquainted with thelimited number of things belonging to the field of science. Thefew conveniences then were learned easily at home, and thepeople were relatively more efficient than now. But inventionsduring the last half century have multiplied so rapidly that thehome has been unable to keep up with them, so that the burdenof making our youth efficient has fallen more and more upon ourschools and colleges. Those institutions as a whole are failingin much of this efficiency work.

Listen to some of the adverse criticisms of science teachingthat are offered: ^School work, especially in science,, is too arti-ficial�not real.7^ ^Most of the science subject-matter taughtremains unused, both in and out of school and college hours andin after school years.^ ^The big problem^of the school is thatthere is very little relationship between the work of the schooland the work of the world.?? ^Our physics books are too much onthe order of encyclopedias or dictionaries, and their proper func-tion is for reference only/7 ^We lack books for high school andcollege which present science as living projects.n ^The basic