Indian Journal of Chemi stry VoI.4SA, Jul y2006, pp. 163 1- 1637

Effect of temperature on the viscosities of some divalent transition metal sulphates and magnesium sulphate in water and

water+ethylene glycol mixtures

M L Parmar'" & R C Thakur

Department of Chemi stry, Himachal Pradesh University , Summer Hill , Shimla 171 OOS , India

Received 6 }allllw)' 2006; revised 15 April 2006

Relati ve viscos ities for the so lutions of some divalent transiti on metal sulphates, viz. manganese sulphate, cobalt sulphate, nickel sulphate, copper sulphate and zinc sulphate; and magnes ium sulphate at different concentrations have been determined in water and in water + ethylene glycol (EG) [S , 10, IS, 20 and 2S% by weight of EG] mi xtures at 303. IS K, and in water and in S% (IV/IV) EG + water at five different temperatures. The data have been analysed using the Jones-Dole equation and the obtained parameters have been interpreted in terms of ion-ion and ion-so lvent interactions. The activation parameters of viscous fl ow ha ve been obtained which depicts the mechanism of viscous now. The transiti on metal sulphates and magnesium sulphate ac t as structure makers/promoters in water and in EG + water mi xtures.

Studies on vi scos ities of ionic solutions are of great help in charac terizing the structure and properties of solutionsl. J(i. Various types of interactions exist between the io ns in the solutions and of these, ion-ion and ion-solvent interactions are of current interest. These interactions help in better understanding of the nature of solute and solvent, i.e. whether the added solute modifies or di storts the structure of the solvent.

The addition of organic solvent to an aqueous solution of electrolyte brings about a change in ion 's solvation and often results in a large change in the reactivity of di ssolved electrolyte. The use of ethylene glycol (EG) + water mixtures has attracted much attention in recent years as solvents in the study of physcio-chemical properties of e lectrolytic solutions. Now-a-days ethylene glycol is being used for the synthesis of nano particles . Thus, EG acts as dispersing, reducing as well as stabilizing medium. The nano particles are highly stable in EG and do not coagulate on long standing. Also, 3d-transition metal ions play a vital role in life systems because of their natural presence in vitamins, enzymes and proteins (Cu, Fe, Mn, Co, Zn , etc.). Ion-ion and ion­solvent interactions in EG + water systems are reported here.

Materials and Methods AnalaR quality manganese sulphate (MnS04'H20),

cobalt sulphate (CoS04'7H20), nickel sulphate (NiS04·6H20 ), copper sulphate (CuS04'5H20) , zinc

sulphate (ZnS04'7H20) and magnesium sulphate (MgS04'7H20), were used after dry ing over P20 S in a desiccator. The reagents were always placed in the desiccator over P20 S to keep them in dry atmosphere.

Freshly distilled conductivity water (sp. condo "" 10.6

ohm-l cm· l) was used for preparing aqueous mixtures of EG as well as standard liquid . EG (AnalaR) was kept over calcium oxide for about 24 h and then decanted and distill ed under reduced pressure. Only the middle fraction was used. The density of EG was found to be 1.1065 g cm·3 at 303.15 K and agrees with the reported value l7 (1.10664 g cm-3).

All the aqueous mixtures of EG as well as the solutions of electrolytes were made by weight and molalities. ' Ill ' were converted into molarities , c, using the standard expression l8: c = 1000 d 11//(1000 + III M2)' where d is the solution density and M2 the molecular weight of an electrolyte.

The density was measured with the help of apparatus similar to the one described by Ward and Millero l9 . The glass sample cell had a bakelite top with a hole in the centre and was placed in a water­bath (± O.OI OC). The glass-float weighed 32.9754 g

and had a volume of 21.6737 cm3 (± 0.000 I) at 303.15 K. Density was calculated using the relation , d = do + (Wo - W)IVj; where d and do are the densities of sample solution and pure water respectively , Wand Wo are the weights of float in the sample solution and water, and VJ is the volume of the float. Accuracy of the system was checked by measuring the density of

1632 INDIAN J CHEM, SEC A, JULY 2006

pure dioxane [measured d = 1.0222 g cm·3 is in good agreement with the reported value20 (1.0223 g cm·3

)].

The relative viscosities were measured at desired temperature using Ostwald's suspended level type viscometer with a flow time 341 s for water at 303.15 K. Runs were repeated until three successive

determinations were obtained within ± 0.1 s. Since all the flow times were greater than 100 s, kinetic energy correct ion was not necessary. The relative viscosities

of the solutions (1]rel) were calculated by the usual procedure21

. Accuracy in viscosity was checked by

determining the viscosity of dioxane. Our value of 1}

= 0.01085 cP is in good agreement with the reported value20 (1.01087 cP). Density and viscosity measurements were carried out in a well-stirred water-bath whose temperature was controlled to

±0.01 °C.

Results and Discussion The relative viscosities and densities of the

solutions of divalent transition metal sulphates, viz. manganese sulphate, cobalt sulphate, nickel sulphate, copper sulphate and zinc sulphate; and magnesium sulphate in water and in binary aqueous mixtures of EG [5, 10, IS, 20 and 25% by weight of EG] were measured at 303.15 K. The experimental results of divalent transition metal sulphates and magnesium sulpahte in water and in binary aqueous mixtures of EG have been analysed by the Jones-Dole equation22

:

11rel = 11111" = 1 + A C'll + B c ... (1 )

where 11 and 1}" are the viscosities of the solution and solvent (water, water + EG), respectively, and c is the molar concentration. A and B are the constants characteristic of ion-ion and ion-solvent interactions respectively.

The plots of (1}r - 1)1 Fc versus Fc for all th~ .. divalent transition metal sulphates and magnesium sulphate, were found to be linear, with least scatter in water and in different compositions of EG + water reported here. A representative plot for magnesium sulphate in different compositions of EG + water at 303.15 K is shown in Fig. I. The values of A and B parameters have been calculated using the least squares method by fitting the experimental results in Jones-Dole equation and these values along with standard errors, obtained in water and in different mixtures of EG + water at 303.15 K, are recorded in Table I.

Table I shows that the values of A coefficients are positive for an individual electrolyre 111 water and in the entire composition range of EG + water at 303.15 K thereby showing the presence of s trong ion-ion interactions. Further, it is also clear from the table that A-coefficient continuously increases with the increase of EG content in water at 303.15 K, for an individual electrolyte, showing that ion-ion interactions are strengthened by the addition of EG to water, which may be attributed to the decrease in the ion-solvation .

It is also evident from Table I that the values of B­coefficients are positive for transition metal sulphates and magnesium sulphate in watcr and in binary aqueous mixtures of EG and also decrease with the increase in EG composition in water suggesting that ion-solvent interactions are further weakened with the increase of EG content in water thereby resulting in the decrease of ion-solvation. In other words, it may be said that EG has more affinity for water than that of an electrolyte. It is also clear from Table I that the magnitude of B-coefficient, for an individual electrolyte, is quite larger as compared with that of A­coefficient, showing that ion-solvent interactions dominate over ion-ion interactions.

The viscosity data have also been analysed on the basis of transition state treatment of relative viscosity as suggested by Feakins et al.23 The B parameter in terms of this theory is given by the following relation:

300

280

~ 260 ~ ..-~ 240 E

N

M 220 E

i' 200 x ~ 180

£: 160

140

1 ~ S'I,EG'H2 o

2 ~ IO'I,EG'HzO

3 A--.C!l 15'1, EG.H20

4 D-i!l 2G 'I. E G' H20

5 ~ 25'>'. EG' H20

, , I

8 12 16 20 24 28 32

vCx102(dm 1/2mor3/2)

Fi~. l-Plots of (17r -1)/ Fc versus Fc for magnesium sulphate in different compositions of ethylene glycol+waler at 303.15K.

PARMAR & THAKUR: VISCOSITIES OF SOME DlVALENTTRANSITION METAL SULPHATES AND MgSO~ 1633

Table I - Values of A and B parameters of Jones-Dole equation for transition metal sulphates and magnesium sulphate in water and in di fferent compositions of EG + water at 303. 15 K (s tandard errors given in parentheses)

EG + water A B (% wlw) (dm3l~ mOI"\I,) (dm' mol"l )

Manganese sulphate o (water) 0.1 13 (± 0.00 I ) 0.323 (± 0.003) 5 0.1 2 1 (± 0.00 1) 0.336 (± 0.002) 10 0.129 (± 0.000) 0.320 (± 0.00 I ) 15 0.135 (± 0.00 1) 0.306 (± 0.00 I ) 20 0. 142 (± 0.000) 0.296 (± 0.002) 25 0. 15 I (± 0.000) 0.273 (± 0.002) Cobalt sulphate o (water) 0.1 24 (± 0.002) 0.303 (± 0.00 I ) 5 0. 120 (± 0.003) 0.297 (± 0.002) 10 0.1 26 (± 0.00 I ) 0.282 (± 0.003) 15 0. 134 (± 0.000) 0.276 (± 0.002) 20 0.1 40 (± 0.002) 0.270 (± 0.001 ) 25 0.146 (± 0.000) 0.258 (± 0.002) Nickel sulphate o (water) 0.123 (± 0.00 I ) 0.2 12 (± 0.002) 5 0.125 (±0.00 1) 0.264 (± 0.004) 10 0. 135 (± 0.00 I ) 0.230 (± 0.003) 15 0. 14 1 (± 0.00 1) 0.2 19 (± 0.004) 20 0. 147 (± 0.001) 0.209 (± 0.003) 25 0. 15 1 (± 0.00 I ) 0.205 (± 0.003) Copper sulphate o (water) 0.12 1 (±0.004) 0.329 (± 0.002) 5 0.1 28 (± 0.002) 0.325 (± 0.002) 10 0.138 (± 0.003) 0.302 (± 0.002) 15 0. 147 (±0.001 ) 0.282 (± 0.003) 20 0.1 52 (±0.00 1) 0.272 (± 0.003) 25 0.1 57 (± 0.00 I ) 0.259 (± 0.003) Zinc sulphate o (water) 0.1 25 (± 0.002) 0.3 15 (± 0.001 ) 5 0.1 30 (± 0.00 I ) 0.330 (± 0.002) 10 0.1 38 (± 0.000) 0.309 (± 0.002) 15 0.145 (± 0.000) 0.296 (± 0.002) 20 0.149 (± 0.(00) 0.287 (± 0.002) 25 0.1 54 (± 0.003) 0.279 (± 0.00 I ) M agnesium sulphate o (water) 0. 109(±0.001) 0.3 16 (± 0.002) 5 0. 120 (± 0.00 I ) 0.284 (± 0.003) 10 0.129 (± 0.004) 0.268 (± 0.00 I ) 15 0. 137 (±0.00 1) 0.25 1 (± 0.002) 20 0.142 (± 0.003) 0.243 (± 0.002) 25 0. 148 (+ 0.002) 0.232 (+ 0.(0 1)

V' - V," V' [/>'11 ~' - />'11"] .. . (2) B = I - +_1_ - I

1000 JOOO RT

where Vlo is the mean volume of the solvent and V10

the partial molar volume of the electrolyte. The free

energy of ac ti vation per mole of pure solvent ( /j,.f. .. l ~· ),

and the free energy of activation per mole of

electrolyte ( 11J1~· ) were calculated24 with the help of

relations (3) and (4), respectively:

11J1~' = RT til ( 1]" VIO IhN) ... (3)

and

where It is the Planck constant, N the Avogadro number, 11" the viscosity of solvent, R the gas constant

and T the absolute temperature. The values of 11J1~' ,

calculated from relation (3) are given in Table 2. For mixed solvents, each solvent mixture was

treated as pure and the molar volume taken as a mean volume defined as:

... (5)

where, Xj, M, and X2. M 2 are the mole fractions and molecular weights of water and ethy lene glycol respectively , and d, is the density of solvent (EG +

water). The values of V,o , the partial molar volume at

infin ite dilution for transition metal nitrates and magnesium nitrate, determined from density data, are

also recorded in Table 2. The values of 11J1~I· and V/l ,

calculated with the help of relations (4) and (5) respectively, are also recorded in the table.

It is ev ident from the data (Table 2) that 11f.1~· is

practically constant at all solvent compos itions,

implying that 11J1~· is dependent mainl y on - -

B-coefficient and (VIO - V1o) terms. It is al so clear

from th ~ tabl e that the values of 11.u~· are pos iti ve and

larger than 11f.1 ~I· whi ch suggest that the formation of

the transition state is less favoured in the presence of transition metal sulphates and magnesium sulphate, meaning thereby the formation of transition state is accompanied by the breaking and distorti on of the intermolecular bonds between ethylene glycol and water, i.e. solvent.

It has been emphasized by many workers25 that dBldT is a better criteri on for determining the structure making/breaking nature of any solute than simply the B-coefficient. So, this means that in order to fo llow this criterion, the temperature effect must be studied.

1634 INDIAN J CHEM, SEC A, JULY 2006

Table 2 - Values of V,U (tilll ' IllOI-I). V!o (dm' mor '). !'J. !-l ~ ' (kJ

mor l) anti !'J.J.I ~j" (kJ mor l

) for transiti on metal sulphates Gnd

magnesiulll sulphate in different composi tions o f EG + water at 303.1 5 K

Parameter EC + waleI' (% IV/IV)

v" ,

5

18.84

9.39

10

19. 16

9.67

Mallgall l'se slIlphatl'

v"

!'J.J.I ~ Coballslllplwle

V2"

19.48

54.42

16. 13

5 1.36

101.32 97.94

59.10 57.35

IS 20

19.9 1 20.64

10.08 10.47

12.59 10. 12

47.88 45.33

95.54 92.53

55.36 53.68

25

21.38

10.82

9.36

41.58

90.6 1

49.40 !'J.J. I ~·

Nickel slI lphate

V," 8Hi4 800 SO .50 76.46 73. 18

!'J.J.I ~ Copper slI lphale

53.91 48.49 45.47 42.8 1 41.09

V,U 57. 16

!'J.!-l ~ 58.00

Zillt" slIlphatl'

V;' 98.54

!'J.J.I ~ 64. 17

Mallgllesilllli slIlphate

v2 11 5.20

!'J.J.i~ 59 .72

52.85

53.S3

97.05

60.43

111.06

57 .56

49.02 46. IS

49.63

94.95

57 .05

106.65

52.83

46.80

94.37

54.52

104.27

50.36

42.47

43.S4

S9.42

51.73

10 1.6 1

47.63 ------------------------------

ElTect 01 tClllpenllurc

Because o f the identical behaviour of individual transiti on meta l sulphate and mag nesi um sulphate in different compos iti ons of EG + water at 303. 15 K, the effect of temperature has been studied in water and

onl y in 5% (IVhv) EG + wate r. The plo ts o f 07, -1)/ Fc versus j;; have been fo und to be linear at

298. 15, 303. 15, 308. 15 , 313.15 and 318.15 K in acco rdance with Jo nes- Do le equation (I), fo r all the transitio n meta l sulphates and mag nesium sulphate. A sample plot fo r copper sulphate in water is show n in Fig. 2 at different temperatures. Values o f A and B parameters have been calculated us ing the least squares method and these values, along with standard errors, are recorded in Table 3.

It is evident from Table 3 that the values of A coefficients are positive for individual transi tion metal sulphate and magnesiu m sulphate in wate r as well as

300

280

~ 260 ~ ....... , o 240 E

N

(ryE 220 u

(")

o 200 ....... x o

'<: 180 ....... ~

~ liS.15K

2 'Y}----'\-J 303.15 K

3 t;:"......6 loa .15 K

4 0-0 3\3 .1 5 K

5 ~ l1S·15K

L-__ ~ __ ~ __ -L __ -L __ -L __ ~I ___ ~ 4 8 12 16 20 24 28 32

v'Cx1 02(dm 1/2mot 3/2)

Fig. 2- Plots o f ( I] ,. - 1)1 JZ versus JZ for copper sulphate in

WGter Gt d i fferent temperatures.

JI1 EG + water (5 % IV/IV) mixture an el continuously increase with the ri se in temperature, thereby suggesting that io n-i on interactio ns are s trengthened with increase of te mperature. In o ther words it may be said that w i th the ri se in temperature the sol vat io n of i ndi vidual transi ti o n metal su I ph ate and magnesi u m sulphate is reduced .

It is al so c lear from Tabl e 3 tha t the va lues o f B­coeffic ients are pos iti ve for al l the transiti on metal sulphates and mag nesi um sulphate in wate r and in EG + water (5 % IV/W) at all temperatures , show ing the presence o f strong io n-solvent interaction s. Further, the value of the B-coeffici ent decreases with the ri se in temperature which suggests that ion-solvent interactions are weaken with the ri 5.e in temperature for all the sulphates in water and EG + water.

The va lue of dB/dT is negati ve for all. the tran sition metal sulphates and magnes ium sul pha te in water as well as in EG + water show ing that the transiti on metal sul phates and magnesium s.ulphate act as s truc ture makers/promo ters in bo th the systems.

The data for viscosity B-coeffic ients at different temperatures have also been analysed by applying the

transition s tate theory. The values of /j.f..l~' and /j.f..lg'

have been calculated with the help of relations (3) and (4) respectively, and are recorded in Table 4 .

PARMAR & THAKUR: VISCOSITIES OF SOME DIVALENT TRANSITION METAL SULPHATES AND MgS04 1635

Table 3 - Values of parameters A (dm"2 mor'I,) and 8 (dm) mo r l) of Jones-Dole equation for transition metal sulphates and magnesium

su lphate in water and in EG + water (5 % IV/IV) at different temperatures (standard errors g iven in parentheses)

Parameter Temperature (K) 298.1 5 303.15 308 .1 5 313.1 5 318.15

Water Mang(lIIese slIlphate

A 0.102 (±0.002) 0.113 (±0.001 ) 0.134 (±O.OOO) 0.149 (±O.OOO) 0.161 (±O.OOO)

8 0.323 (±0.003) 0.302 (±O.OO I ) 0.283 (±O.OO I ) 0.266 (±0.002) 0.249 (±O.OO I ) Cobalt slIlphate

A 0. 105 (±O.OO I ) 0.124 (±O.OOO) 0.146 (±0.001) 0.170 (±O.OO I) 0. 187 (±O.OOO)

8 0.303 (±O.OO I) 0.300 (±0.004) 0.299 (±0.003) 0.281 (±0.003) 0.262 (±0.002) Nickelslliphate

A O. 108 (±O.OOO) 0.1 23 (±O.OO I) 0.135 (±O.OOO) 0.146 (±0.001) 0.156 (±O.OOO)

8 0.2 19 (±0.002) 0.212 (±0.002) 0.209 (±0.002) 0.207 (±0.003) 0.205 (±O.OO I) Copper slIlphate

J\ 0.102 (±0.001) 0.12 1 (±O.OOO) 0.142 (±O.OOO) 0.161 (±O.OOO) 0.180 (±0.002)

B 0.341 (±0.002) 0.329 (±0.002) 0.313 (±0.002) 0.299 (±0.002) 0.305 (±O.OO I ) Zinc slIlph({fe

A 0.102 (±O.OO I) 0.125 (±0.002) 0.140 (±0.002) 0.159 (±O.OO I ) 0.179 (±O.OO I )

8 0.339 (±0.003) 0.315 (±O.OO I ) 0.324 (±O.OO I ) 0.312 (±0.003) 0.298 (±0.003) Magnesilllll slIlphate

A 0.090 (±O.OOO) 0.109 (±O.OO I) 0.121 (±O.OO I) 0.140 (±O.OO I ) 0.153 (±O.OO I )

8 0.340 (±0.002) 0.335 (±0.002) 0.326 (±0.004) 0.316 (±0.004) 0.306 (±0.004)

5% (IV/IV) EC + lVater Mangan ese slIlphate

A 0.103 (±O.OO I) 0.121 (±0.00 1)

8 0.351 (±0.003) 0.336 (±0.002) Cobalt slIlphate

J\ 0.096 (±0.002) 0.1 20 (±0.003)

8 0.306 (±O.OO I ) 0.297 (±0.002) Nickel slIlphate

A 0.106 (±0.003) 0.125 (±O.OO I )

8 0.283 (±O.OO I) 0.264 (±0.004) Copper slIlphate

A O. 105 (±O.OO I ) 0.128 (±0.002)

8 0.349 (±0.002) 0.325 (±0.002) Zinc slIlphate

A 0.105 (±O.OO I) 0.130 (±O.OO I )

B 0.350 (±O.OO I ) 0.330 (±0.002) Magnesilllll slIlphate

A 0.098 (±O.OO I ) 0.120 (±O.OO I)

8 0.303 (±0.002) 0.284 (±0.003)

. ~ ~ ~ According to Feakll1s model- , D.J..l2 > D.J..l1 for

the solutes having positive B values. The greater the

value of D.J..l~· , the greater is the structure making

ability of the solute. Thus, it may be concluded from these results that Zn"2+ ion is an efficient structure maker, the Mn2+ and Ni 2+ ion s are least (SO/+ being common). The order of structure making is therefore:

0.138 (±0.002) 0.156 (±0.002) 0.170 (±0.00 1)

0.306 (±O.OO I ) 0.283 (±0.004) 0.260 (±0.003)

0.137 (±O.OO I ) 0.153 (±O.OO I ) 0.169 (±0.001)

0.260 (±0.003) 0.245 (±0.004) 0.235 (±0.004)

0.142 (±0.003) 0.162 (±0.001) 0.174 (±0.001)

0.247 (±0.002) 0.224 (±0.004) 0.216 (±0.003)

0.149 (±0.001) 0.165 (±0.002) 0.179 (±0.002)

0.306 (±0.004) 0.293 (±O.OO I ) 0.272 (±O.OO I )

0.1 54 (±O.OO I ) 0.171 (±0.00 1) 0.183 (±O.OO I )

0.309 (±0.004) 0.284 (±0.002) 0.272 (±0.002)

0.136 (±O.OO I ) 0.151 (±0.001) 0.168 (±O.OO I )

0.273 (±0.003) 0.259 (±0.003) 0.254 (±0.002)

According to Feakins model, D.J..l~· decreases with

the increase of temperature for the solutes having negative values of dB/ciT. This is nicely shown by all the divalent cations i.e. Mn2+, C02+, Ni2+, Cu2+, Zn2+ and Mg2+, which act as structure makers .

It is also evident from Table 4 that the quantity

(D.J..l~' -D.J..l~' ), the change in activation energy per

mole of solute on replac ing one mole of solvent by one mole of solute at infinite dilution, is positive and

1636 IND IAN J C HEM. SEC A. JULY 2006

Table 4 - Val ues o f \1,0 (dm' ma r '), \I " (dm' mo l-I). I'1p:' (kJ

1110 1" ) and I'1p~ (kJ mor ' ) fo r tran siti o n metal sul phates ami

magnesium sul pli ate III EG + wa ter (5 % 11 / 11") at d i ffe re nt temperatures

Parameter Te mpe rature (K) 29X. 15 303. 15 30S. 15 3 13. 15 3 1S. 15

\I " , 18.1) 1

9.53

Mallgall ese slI/pilale

\I,ll 22 .52

56.27

Coball .l /tfpilme

\1;' I O-+' I I

1'1~1 ~ 58.S6

Nickel slilp/wle 9 1.50

1'111 ~ 56.4 0

Copper slI lpilole

\1,"

1'111 ~ Zillc slIipilme

\I:)

60. 17

60.97

102.74

66.71

Magliesilllll slI lpilate

\1;'

~ .-

741 70 r

66l o 62

~ 58

~ "f 50

46

42

11 5.74

62.23

18.84

9.39

19.48

54.42

I {) 1.32

57.35

S7 .64

53 .9 1

57. 16

58.00

98.74

64. 17

111.06

59.72

18.88

9.2S

15 .91

50.40

97. 18

55. 19

83 .50

5 1.56

52.13

55.32

96.40

6 1.73

105.76

5S. 11

IS.9 1

9. 17

12. 15

47 .20

94. 12

53.26

SO.26

4S.46

50.76

53.90

93.29

5S.5 1

10 1.59

56.2 1

I I I I I

18.95

9.08

7.75

9 1.8 1

52.05

7703

47 .34

48.3 1

5 1.1 4

88.82

56.S0

96.55

55.36

298.15 303.15 308. 15 313.15 318.15 T(K)

Fig. 3- Varia ti on o f l'1~l 20 ' with temperature fo r manganese sul pha te. copper sulphate and zinc sulphate in 5% e thy lene g lyco l­WOlle r mi xture.

Tablc 5 - Entropy, T I'1S;" ( kJ mar' ) :IIlJ cnthal py. M/~

( kJ mo l-I) of acti va ti on fo r viscous fl ow Il " transiti on metal sulpha tes and magnesium sulphate in EG + water (5 '70 1I 'i1l ') at eli Ile rent temperatures

Parameter

298. 15

MOligollese SII /p ilole

T I'1S~ 190.S2

M/ ~ 247.09

CobO/ISIl/p/wle

T I'1S~ 104. 35

M/~ 163.2 1

Nickel SII/pilole

T I'1S~ 140. 13

1'11/ ;' 196.53

Copper SII/p/wle

T I'1S;' 143. 11

1'1 // ;' 204 .08

Zillc SII/p/WIC

T I'1S;' 152.06

1'11 /;' 2 1lU7

Magll('silllll slI/pilmc 101.3 7

Temperat ure (K)

303. 15 30S. 15 3 13.1 5

194.02 197.22 2(10.42

248.44 247.62 247.62

106. 10 107.85 109 .60

163.45 163.04 1(-,2);6

142.48 144.8 3 1-17. IS

196.39 196. 39 195.64

145.5 1 147.9 1 150. 3 1

203.5 1 203 .23 204. 2 1

154.6 1 157. 16 I ~9 . 7 1

2 18.78 2 18.89 2 IS.22

103.07 104.77 106.47

163.60 162.79 I 62. I)S 162 .6S

:W;I)

203.62

247.·n

111 .35

163 .40

149.53

1l)6. g7

152 .7 1

2()U5

162.26

2 19.06

IOS. 17

163.53

large for transiti on metal sulphates and magnesium sulphate studied in 5% ( IV/IV) EG -+- \ova teI' at different temperatures. Therefore , it may be co ncluded fro m these data that the formation of the transiti on state is accompanied by breaking/di stortion of the intermolecula r bonds of the solvent. In oth er words. the fo rmation of transition state is less favoured in the presence of transiti on metal su lphates unci magnes ium sulphate in the entire temperature range .

The entropy of acti vat ion for transi ti on metal nitrates and magnesiulll nitrate has al so been calculated from the foll owing relation2

:l :

... (6)

The values of I'1S~)' have been calcJ lated from the

slopes of linear plots of 1'1/-l~' versus T, shown in

Fig. 3 a sample plot, by using the leas t squares

method. The values of T 1'15:" at different

temperatures are li sted in Table S. The ac ti vation

enthalpy (I'1H ~)' ) has been calculated with the help of

f II ' . ", a ow tng express lOn-' :

PARMAR & THAKUR: VISCOS ITIES OF SOME DIVA LENT TR ANS ITI ON METAL SULPHATES AN D MgSO~ 1637

'" (7)

and the va lues are also recorded in the table. It is ev ident from Table 5 that both enthalpy and

entropy of acti va tion are pos iti ve for all the transition metal sulphates and magnesium sulphate in 5% (IV/IV) EG + water mi xture at different temperatures, which suggest that the transition state is assoc iated with bond breaki ng and decrease in order. This suggests that the slip-plane is some where in the centro­sy mmetric region.

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