Indian Joumal of ChemistryVol. 34A, July 1995, pp. 556-562

Ion association and solvation of silvermonocarboxylates in water + mannitol and

water + sorbitol mixtures at differenttemperatures: A conductivity study

U N Dash- & E R PattanaikDepartment of Chemistry,

Utkal University, Bhubaneswar 751004

Received 21 September 1994; revised 25 November 1994; ac-cepted 23 December 1994

The conductivities of silver acetate, silver propion-ate and silver benzoate have been measured in wa-ter + 5 wt% mannitol and water + 5 wt% sorbitol at20, 25, 30 and 35°C, and analysed using Fuoss-Hsiaequation in the form of Fernandez-Prini coefficientsand Shedlovsky and Fuoss':Kraus extrapolation tech-niques for calculating the association parameters (A 0

and KA)' A comparison of these parameters revealedthat the Shedlovsky method is superior to other meth-ods and predicted better association constants for thesilver monocarboxylates in these aqueous isomericsolvents.

Dash and coworkers I reported the solubility pro-ducts of silver acetate, silver propionate and silverbenzoate in aqueous and aquo-organic solvent(e.g., methanol, ethanol, l-propanol, 2-propanoland urea) media at different temperatures. Inaqueous medium the solubility products reportedfor silver acetate, silver propionate and silver ben-zoate at 25°C are 2.295 x 10-3, 1.616 X 10-3, and7.929 x 10-5 mof dm ", respectively. Since thesesilver monocarboxylates-are fairly soluble in aque-ous and mixed solvent media, it is of interest todetermine their transport properties, such as con-ductivity, viscosity, etc., in aqueous mannitol andaqueous sorbitol. In continuation of our study onthe determination of association constants/ of anumber of 1:1- and 1:2-electrolytes in differentaquo-organic solvent systems from conductancedata, the present work aims at determining theconductivity values of silver acetate, silver prop-ionate and silver benzoate in water + 5 wt% man-nitol and water + 5 wt% sorbitol at 20, 25, 30,and 35°C to examine the validity of Shedlovsky,Fuoss-Kraus and Fuoss-Hsia conductance equ-ations in evaluating the association parametersand to study the behaviour of silver carboxylateion-pairs in these isomeric solvents.

•

ExperimentalSilver acetate (SA), silver propionate (SP) and

solver benzoate (SB) were prepared by the meth-od as described elsewherel-', and dried over P20Sunder vacuum before use. Their purity waschecked by estimation of the silver contents b~potentiometry. Mannitol (BDH, AnalaR) andsorbitol (Loba chemie) were used as such. Con-ductivity water (1(= 1 x 10-6 S cm-I) was usedfor preparing 5 wt% mixed solvents. The con-centrations of solvent mixtures are expressed as% w/w. Mannitol and sorbitol contents in the sol-vent mixtures were accurate to within ± 0.02%.Silver salt solutions were prepared on molal basisby dissolving known weights of the silver salts inappropriate weights of the respective solvents,and conversion of molality into molarity was doneby using the standard expression" considering thedensity differences at the respective temepratures.Conductance measurements were made on a digi-tal reading conductivity meter (Systronics, Type304) with a sensitivity of 0.1% and a dipping typeconductivity cell with platinized electrodes (cellconstant, 1 S em - I). The experiment was repeat-ed several times with different concentrations ofthe silver salts. All measurements were carriedout in water thermostat maintained at appropriatetemperatures varying within ± 0.05°e. The con-ductivities of silver salt solutions were always cor-rected for the conductivities of the solvents used.The specific and molar conductances are ex-pressed in S em -I and S em? mol-I, respectively.

Results and discussionThe conductivity values of silver acetate, silver

propionate and silver benzoate in 5% (w/w) eachof mannitol +water and sorbitol + water mixturesat 20, 25, 30 and 35°C are presented in Table 1.The conductance data were analysed using threemethods, viz., Fuoss-Hsia (FH) equations, Shed-lovsky (S) extrapolation technique" and Fuoss-Kraus (FK) extrapolation technique",

FH equation with Femandez-Prini coefficientscan be written as,

A = Ao - s(ac)l!2 +Eu clnmc) +Jla c

- J2(ac) 3/2- KAA f~ n c ... (1)

where the symbols have their usual significances.

NOTES 557

The molar concentration, c was derived from the and M2 is the molecular weight of the concernedmolal concentration, mby the relation", silver salt. Following the procedure of Justice" and

c = md(1 +0.001 mM2tl ... (2)Pethybridge and Spiers", the values of Au and KAfor silver salts were determined. An initial value of

where d is the density of the silver salt solution in A 0 was estimated from linear extrapolation of Athe solvent concerned at a particular temperature versus cl!2 plot. This value was used to determine

Table 1 - Specific conductance (Ken" X 106 S ern - I) of silver salts in water + 5 wt% mannitol and water + 5 wt% sorbitol at differenttemperatures

Silver 5wt% (X 103 Kco" X 106 (S cm -I)salt additive mol drn "?

20 25 30 35°C

Acetate mannitol 0.64 62.4 66.8 67.3 81.00.84 82.4 89.8 96.3 105.01.16 113.4 125.8 134.3 146.01.56 153.4 164.8 176.3 192.01.60 155.4 167.8 180.3 196.01.71 164.4 177.8 188.3 206.0

sorbitol 0.64 60.5 66.2 72.9 78.40.84 78.5 87.2 94.9 102.41.16 107.5 119.2 130.9 141.41.56 144.5 158.2 172.9 188.41.60 147.5 162.2 176.9 192.41.71 ' 157.5 172.2 187.9 204.4

Propionate mannitol 0.64 37.4 41.8 45.3 49.00.84 49.4 54.8 59.3 65.01.16 69.4 75.8 82.3 89.01.56 91.4 100.8 109.3 119.01:60 92.4 102.8 111.3 120.01.71 98.4 107.8 117.3 128.0

sorbitol 0.64 63.5 70.2 75.9 &2.40.84 82.5 91.2 98.9 106.41.16 114.5 126.2 135.9 148.41.56 151.5 167.2 181.9 196.41.60 154.5 171.2 185.9 200.41.71 164.5 182.2 196.9 216.4

Benzoate mannitol 0.06 10.8 11.9 12.7 14.10.0608 10.9 12.0 12.8 14.20.0624 11.1 12.2 13.0 14.50.0645 11.4 12.5 13.4 14.90.0666 11.7 12.8 13.8 15.30.0687 11.9 13.2 14.2 15.6

0.07 12.1 13.4 14.4 15.8

sorbitol 0.06 15.5 16.2 16.9 18.40.0605 15.6 16.3 17.0 18.50.0611 15.7 16.4 17.2 18.60.0621 15.9 16.6 17.4 18.90.0634 16.2 17.0 17.7 19.30.0643 16.4 17.1 17.9 19.50.0655 16.7 17.4 18.2 19.8

5wt% mannitol D 79.66 77.83 76.06 74.231001'] 1.2052 1.0041 0.9489 0.8535

5wt% sorbitol D 79.66 77.83 76.06 74.23100'7 1.1048 0.9872 0.8709 0.7861

558 INDIAN J CHEM, SEe. A, JULY 1995

the Onsager slopeis), the degree of dissociation,a and mean ionic activity coefficient, f± as follows:

s = 82.4(Df)-ll21]+8.20X lOS(Dft312 (3)

a = AI A, (4 )

and

1.824 x 106(Dfr3!2 (ac )1/2

-logj± =1+atl50.29XlOH(DffI/2(ac)l'2'" (5)

where D is the dielectric constant of the solventconcerned, 1] is the coefficient of viscosity, T isthe temperature in degree Kelvin, and an, the dis-tance of closest approach of ions, is taken as qthe Bjerrum critical distance, i.e., a" =q = z + z_e2 I2 DkT, where the symbols have their usual mean-ings. Using the values of the dielectric constantsof 5 wt% mannitol and 5 wt% sorbitol mixturesavailable in literature!" at different temperatures(shown in Table 1) and that of 1] measured in thislaboratory at different temperatures (shown in.Table 1), the values of s, a, and logf± were esti-mated by the respective equations. These valueswere used to estimate the approximate values ofA 0 and K A from the intercept and slope, respect-ively, of the linear plot of IIA versus A f~ c. Thevalues of E, J land J 2 of Eq. (1) were evaluatedby the equations described by Justice and Pethy-bridge et al. All these values were substituted inEq. (1) along with s, a and f± values obtainedfrom the new A 0 value to determine a new A va-lue. Again the linear extrapolation of the plot of1IA versus A f~ c yielded more accurate A 0 andK:". values from the intercept and slope, respecti-vely. The procedure was repeated using thesefresh values of A 0 and KA until there is nochange in the values of A 0 and KA• The standarddeviation (0) values in A were estimated from theequation,

o = [~ (A exp - A cal )2]112(N-3) ... (6)

and are shown in Table 2. The final values of A 0

and KA evaluated by Fuoss-Hsia equation are giv-en in Table 3.

Shedlovsky method involves the linear extrapo-lation using the equation of the type,

1 1 (KA) [ 2 ]A s(z) = ~ + A G cA f ± s(z) ... (7)

where s(z) = 1+ z + z2/2 + z3/8,z = s( A e)ll2 I A612,

and a = A s(z)1 A 0

Like in FH equation, an initial value of A 0 wasobtained from the intercept of the linear plot of Aversus ell 2 . This value was used in Eq. (3) to cal-culate the Onsager slope, s. Using these s and A 0

values, z, s(z) and a values were calculated as de-fined in Eq. (7). The values of f± were evaluatedusing Eq. (5) with a? =0, q and 2q. From the line-ar plot of 1/ A s(z) versus eA f~s(z) (Eq. 7), theA ° and KA values were evaluated from the inter-cept and slope, respectively, As in the previouscase, the procedure was repeated using these newvalues of A 0 and KA till the constancy in A 0 andKA values appeared.

The Fuoss-Kraus extrapolation method involvesthe equation of the type,

F(z)1 A = II A 0 + (K,/ A 6)(eA fVF(z)) ... (8)

where F(z) = (4/3)cos2{(11 3)cos -1[( - 3)l.S(z/2)]}a = AI Ao F(z)

and z is the same as defined in Eq. (7).

Table 2 - Values of standard deviation (0) obtained {or silver acetate (SA), silver propionate (SP) and silver benzoate (SB) in wa-ter + 5 wt% mannitol and water + 5 ws% sorbitol at different temperturesT Values of 0

°Cwater + 5 wt% mannitol water + 5 wt% sorbitol

SA SP SB SA SP SB20 0.42 0.07 0.37 0.41 0.39 0.63

25 0.48 0.09 0.36 0.43 0.52 0.56

30 0.39 0.06 0.58 0.27 0.60 0.86

35 0.29 0.13 0.67 0.53 0.33 0.59

NOTES 559

Table 3 -/\ 0 and KA values obtained for silver acetate (SA), silver propionate (SP) and silver benzoate (SB) using FH equation fora" =q in water + 5 wt% mannitol (m) and water + 5 wt% sorbitol (s) at different temperatures

Solvent T A U (S ern- mol- I) KA (drn' mol- I)°C

m

s

20253035

20253035

SA94.47

105.62-106.38129.16

94.58104.94115.58123.05

SP58.7765.8971.2577.43

100.16110.49119.19128.38

SB272.46270.44255.56337.24

311.24333.68346.55358.98

SB13382.828715.974496.68

10885.28

4320.765092.954903.483534.97

SA21.6323.3919.5465.83

41.0449.9658.0741.05

SP

36.8653.8650.4251.91

47.8046.0943.3036.64

The values of A 0 and KA were estimated by fol-lowing the iteration process similar to that de-scribed in the case of Shedlovsky method.

All the calculations were carried out on IBMcompatible PC/XT computer, and the results areshown in Tables 2 to 5.

A perusal of Tables 3 to 5 shows that the va-lues of A () and KA are derived from three meth-ods with a" = q in FH technique, and a? = 0, q,and 2q in both Sand FK techniques for calculat-ing activity coefficients. As observed, the A 0 va-lues obtained in Sand FK techniques are veryclose to each other but found to be more thanthat obtained in FH technique. In general, the dif-ferences in the obtained A 0 values can be inter-preted as a superposition of two effects: (1) var-ious limiting conductivities of the solvated ions,and (2) different extents of the association be-tween cation and anion in solutions. Both effectsseem to result from such structural factors as thepossibility of a rapidly changing solvent structureand dielectric constant in the zone of solvent sur-rounding the ions and the effective sizes of thesolvated ions due to the replacement of aqueoushydrates by organic, solvates. These effects areprobably more marked with the values of A 0 de-rived from the more general conductivity equationproposed by Fuoss and Hsia" using Fernandez-Prini coefficients where the A 0 values show alarge difference from those evaluated by the othertwo techniques. It may, therefore, be concludedthat the Sand FK techniques are more appropri-ate than the FH equation for estimating the A 0

values of the silver salts in the mixed solvents(e.g., mannitol + water and sorbitol +water, inwhich the additives are diastereoisomers) in con-tradiction to the conclusion made by other work-ers II where they considered the FH equation tobe more accurate over the Sand FK methods in

predicting the association parameters of the saltsin aqueous and aqueous methanol solutions.

A comparison of the present A, data with thecorresponding values in water is difficult becauseof the lack of relevant data in water at all temper-atures for all the studied silver salts. However,available data II at 25°C in water for silver benzo-ate (A 0 = 94.40 S ern? mol-I) show that the A 0

values are more in water + 5 wt% mannitol andwater + 5 wt% sorbitol mixtures than in water. Inother words, the conductivity of silver benzoateincreases due to the addition of mannitol orsorbitol to aqueous medium.

As observed, the A 0 values of the silver salts inany solvent follow the increasing order: Ao(SP)(ex-cepting in aqueous sorbitoI)<A o(SA)<A o(SB)Thus, the obtained A 0 values for the silver mono-carboxylates may be interpreted, as a first approx-imation, in terms of the co-ordination model ofsolutions. Since the cation (i.e., silver ion) is com-mon in all the salts studied in the present case,the observed differences between the A 0 valuesof the silver salts may be attributed to the differ-ences in the transport properties of the solvatedanions, e.g., carboxylate ions, which reflect factorsaffecting their effective sizes. Of the factors, whichinfluence the sizes of the silver carboxylates canhe radii of the nonsolvated carboxylate ions andthe interionic distance between Ag + and carboxy-late ion. Both these factors influence the sol-vodynamic radii of the ions in the solution andhence influence the A 0 values. Indeed, the A 0

values of the silver carboxylates follow the orderof decreasing solvodynamic radii, that is,A o(SB)> A o(SA) > A o(SP). Thus, it may he con-cluded that the solvodynamic radii of the saltsplay an important role in influencing the ionicmobilities and hence the differentiation of theconductivities of the silver salts. Unfortunately, it

560 INDIAN J CHEM, SEe. A, JULY 1995

Table 4 - A" values obtaine~ for s.ilver acetate (S:), silve.r propionate (SP) and silver benzoate (SB) usingShedlovsky (S) and Fuoss-Kraus (FK) techniques In water + 5 wt Yo mannitol (m) and water + 5 wt% sorbitol (s) at different temperatures

Silver Solvent T Ao{Scm2mol-l)

salt °CSetechnique FK-technique

aO=O =q =2q a"=O q 2q

SA m 20 99.51 99.51 99.51 99.50 99.51 99.5125 108.05 108.05 108.51 108.04 108.05 108.0530 108.98 109.oI 109.03 108.99 109.01 109.0335 131.72 131.71 131.70 131.72 131.71 131.69

s 20 96.59 96.59 96.59 96.59 96.58 96.5825 107.16 107.15 107.15 107.15 107.15 107.1430 118.02 118.02 118.oI 118.02 118.01 118.0035 125.88 125.88 125.87 125.87 125.87 125.87

SP m 20 60.49 60.49 60.50 60.49 60.49 60.49

25 67.84 67.84 67.83 67.83 67.83 67.8330 73.35 73.35 73.35 73.34 73.34 73.3435 79.76 79.76 79.75 79.75 79.75 79.75

s 20 102.19 102.18 102.18 102.18 \02.18 102.1725 112.76 112.76 112.75 112.76 112.75 112.75

30 121.76 121.76 121.75 121.76 121.75 121.75

35 131.27 13i.27 131.26 131.27 131.26 131.26

SB m 20 274.18 274.19 274.14 274.19 274.15 274.15

25 273.02 273.03 273.02 273.05 273.03 273.02

30 256.60 256.56 256.58 256.59 256.55 256.56

35 339.79 339.76 339.74 339.79 339.76 339.74

20 312.21 312.21 312.18 312.21 312.21 312.16

25 336.57 336.52 336.55 336.52 336.52 336.49

30 347.47 347.42 347.37 347.44 347.41 347.34

35 360.30 360.21 360.28 360.30 360.33 360.22

is not possible at present to evaluate the solvody-namic radii and examine quantitatively in solu-tions. Despite this fact, we must emphasize thatthe differentiation of conductivities of the investi-gated silver salts can be most probably accountedfor by the extent of ion-solvation and the ion-pairassociation. The weaker solvation and the greaterion-pair association increase ionic mobility andhence the conductivity.

Association constants (KA) estimated from FHmethod taking a" = q, and from S and FK meth-ods taking a'' = 0, q and 2q are presented in Table5. Our investigations of the salts show a consider-able ion-pair association. On such cases, devi-ations from the limiting Onsager and Debye-Huckel equations can be attributed almost whollyto the strong cation-anion electrostatic interaction.A larger ion-pair association of silver benzoateobtained in the mixed solvents can be attributedto less anion stability and to the lack of solvation

of the ion, while reverse is the case with silverpropionate, which gives smaller ion-pair associa-tion. The variation in the values of KA can beinterpreted in terms of the effect of the anion(since cation is the same in all salts) on the struc-ture of the solutions. A structure breaking ion, ingeneral, possesses high mobility and increases theconductivity leading to a high value of KA. Thehigh values of A 0 and KA for silver benzoate sup-port this view. Any change in the association con-stant for a particular salt on passing from one sol-vent to another, and with change of temperatureis due to the different extents of the association ofthe ions in solutions. It is found that the KA valueof silver benzoate in water" (KA = 23.61 drn"mol- I) at 25°C is smaller than that in aqueousmannitol or aqueous sorbitol at this temperature.The change in KA value on passing from water towater +mannitol or water + sorbitol mixtures mayagain be accounted for the different extents ofion-solvation in the solutions.

NOTES 561

Table 5 - K (dm" mol-') values for silver acetate (SA), silver propionate (SP) and silver benzoate (SB) obtained using Shedlovsky(S), and Fuoss-Kraus (FK) techniques in water + 5 wt% mannitol (m) and water + 5 wt% sorbitol (s) at different temperatures

Silver Solvent T KA (dm' mol-')salt ·C

S-technique FK-technique

aO=O =q :!2q aO=O q 2q

SA m 20 2.56 2.53 2.51 3.08 3.05 3.03

25 2.66 2.62 2.56 3.27 3.22 3.18

30 41.98 41.66 41.37 42.53 42.20 41.91

35 34.23 34.01 33.81 33.54 33.33 33.14

s 20 12.09 12.01 11.93 11.43 11.36 11.29

25 19.54 19.42 19.31 18.85 18.74 18.63

30 25.67 25.51 25.36 24.93 24.77 24.6335 10.21 10.14 10.09 9.46 9.40 9.35

SP m 20 0.48 0.50 0.51 0.61 0.59 0.5725 11.11 12.04 11.98 10.83 10.77 10.7230 9.73 9.68 9.63 8.49 8.45 8.40

35 10.02 9.96 9.91 8.71 8.67 8.62

s 20 19.11 18.99 18.89 18.48 18.37 18.2725 17.16 17.05 16.95 16.52 16.42 16.3230 13.66 13.58 13.50 12.98 12.90 12.8335 7.24 7.19 7.15 6.55 6.50 6.46

SB m 20 13372.44 13369.54 13361.16 13374.75 13366.03 13361.7625 8817.74 8816.72 8814.51 8819.88 8816.72 8813.2630 4405.89 4402.95 4401.34 4404.84 4399.82 4401.5035 10837.74 10831.61 10828.75 10837.74 1083l.61 10827.30

20 4241.11 4240.89 4235.26 4243.22 4240.89 4238.7725 5167.96 5164.22 5164.77 5166.45 5167.36 5158.2730 4790.18 4781.93 4778.67 4785.54 4783.09 4774.0535 3457.09 3456.90 3456.01 3454.53 3460.56 3450.35

The KA values as given .in Table 5 for differentsilver salts deviate to a larger extent in comparis-on to A 0 values (Table 4). The values of KA ob-tained using FH method are quite large in com-parisqn to that obtained using Sand FK methods.However, the deviation is less when the valuesobtained by Sand FK methods are taken intoconsideration. In both the latter techniques, thevalues of KA for all= 0, q and 2q decrease forthese salts except for SA in 5 wt% mannitol at20, 25 and 30"OC,for SP at 20°C in 5 wt% manni-tol. It is also evident that KA values obtained by Smethod with a'' = 0 are the nearest to the valuesobtained using FH equation in spite of consider-able deviations. Hence, it can be concluded thatany technique, S or FK, could be used to deter-mine the A 0 values, but KA values obtained bythese methods differ from each other to a largeextent. But the relative merits of FH, S and FKmethods could be assessed by comparing the A 0

and KA values obtained from these three meth-ods. Taking the deviations in the obtained A 0 and

KA values into consideration on the whole, itcould be concluded that the Shedlovsky techniqueis superior to the FK method. Nevertheless, inview of the evaluation of the association parame-ters, FH and FK methods are also more useful.

Walden products for silver carboxylates in var-ious solvents at different temperatures were esti-mated using the relation A 01], where A ° is the li-miting molar conductivity (Table 4) and 1] is theviscosity of the solvent concerned (Table 1) andare given in Table 6, using the Shedlovsky tech-nique for the A 0 values. The mean activity coeffi-cients of the silver salts needed for the evaluationof A 0 and KA values (Eq. 7) were computed us-ing Debye-Huckel extended equation (5) witha'' = 0, q, and 2q. Considering the solvent separat-ed ion-pairs, the medium activity coefficients wereused for evaluation of A 0 values with a" = q, andthese A (I values were taken into consideration forestimation of Walden products of the silver salts.

A comparison of the present A ()1] values of thesilver salts with that in water is difficult because

562 INDIAN J CHEM, SEe. A, JULY 1995

of lack of relevant data for these silver salts at alltemperatures. However, the reported 1\ orJ valuefor silver benzoate in water at 25°C(1\ orJ= 0.840)11 shows that the values of 1\ orJ ob-tained in the present investigation are higher inaqueous mannitol and aqueous sorbitol than inwater. Since the Walden products give an infor-mation regarding ion-solvent interactions, appreci-able variation in the Walden product as a functionof the solvent is generally regarded as an index ofspecific ion-solvent interactions including structu-ral effects. A reasonable constancy of the Waldenproduct for silver acetate in aqueous mannitoland aqueous sorbitol at different temperatures in-dicates that there is not much change in the solva-tion of the silver acetate ion-pairs with change insolvent as well as with change in temperature.However, solvation effects are reflected in thevariation of Walden products of silver propionateand silver benzoate with change in solvent. As ob-served, silver benzoate exhibits considerable var-iation in its Walden products with temperaturewhile silver propionate shows almost a constantvalue of Walden product at different tempera-tures. The variation in the values of 1\ 0 rJ can beinterpreted in terms of the effect of the anion(since cation is the same in all salts) on the struc-ture of the solutions. A structure breaking ion, ingeneral, possesses high mobility and decreases thelocal viscosity leading to a high value of 1\ 0 rJ.The higher values of 1\ Q n for silver benzoate inboth the mixed solvents at all temperatures sup-port this view.

It is now possible to estimate separate ionicconductivities of carboxylate ions from those ofthe silver salt obtained in water + 5 wt% mannitoland water + 5 wt% sorbitol mixtures. Followingthe Walden's rule." that the Walden product(1\ orJ) of the anion is constant in a wide variety ofsolvents including water, the Ao values for acetate,propionate and benzoate ions are computed as36.40, 31.86, and 28.82 S ern? g ion - I, respect-ively, in water + 5 wt% mannitol, and 37.02,32.40, and 29.32 S em? g ion - I, respectively, inwater + 5 wt% sorbitol at 25°C, which are foundto be lower than the corresponding values (40.90,35.80, and 32.38 S ern? g ion - 1 for acetate, prop-ionate and benzoate ions, respectively) availablein water'? at this temperature. Thus it may beconcluded that the carboxylate ions are preferen-tially hydrated in water + mannitol and wa-

Table 6 - A uTI values of silver acetate (SA), silver propionate(SP) and silver benzoate (SB) in water + 5 wt% mannitol (rn) and

water + 5 wt% sorbitol (s) at different temperaturesSilver Solvent A 0 TI values atsalt

SA20

1.201.07

0.731.13

3.303.45

301.031.03

0.701.06

2.433.03

35°C1.120.99

0.681.03

2.902.83

251.081.06

0.681.11

2.743.32

m

SP m

SB ms

ter + sorbitol mixtures, and the higher 1\ 0 valuesand hence the higher 1\ (I rJ values of the silversalts obtained. in aqueous mannitol and aqueoussorbitol as compared to that in water (from thereported values of silver benzoate) might arisefrom the contribution of Ag ' ion which is consid-ered to be as a structure breaker in these mixedsolvents.

References1 (a) Dash U N, Behaviour of electrolytes and electrode sys-

tems in solutions with reference to ion-solvent interactions.D.Sc. thesis Utkal University. 1991.(b) Dash U N & Rath P C, Thermochim Acta, 16 (1976)407.(c) Dash U N & Kalia S P. Fluid phase equilibria. 40

• (1988) 153.2 (a) Dash U N, Das B B, Biswal U K & Panda T, J elec-

trochem Soc. India, 33 (1984) 239; 36 (1987) 171.(b) Naik S K & Dash UN. Trans SA EST. 24 (1990) 141.(c) Pattanaik E R & Dash U N, Trans SAEST. 28 (1993)79.

3 Nayak B & Dash UN, J. electroanal Chern, 41 (1973)323.

4 Robinson R A & Stokes R H. Electrolyte solutions. (But-terworths, London), 1955, pp. 30.

5 (a) Fuoss R M & Hsia K L, Proc Natl Acad Sci, USA, 57(1966)1550;58(1967)1818.(b) Fernandez-Prini R. Trans Faraday Soc. 65 (1969)3311.

6 Shedlovsky T & Kay R L, J phys Chern, 60 (1956) 151.7 Fuoss R M. J phys Chern. 79 (1975) 525. 1983; 81

(1977) 1829.8 Justice J C, J chim Phys, 65 (1968) 353; Electrochim A~

ta,16(1971)701.9 Pathybridge A D & Spiers D J. J chem Soc. Faraday I.

(1976) 64; (1977)768.10 (a) AkeriofGJ,JAmchemSoc,54(1932)4125., (b) ref. 1.II Maniah V. Sethuram B & Rao T Navaneeth, Bull Soc

Chim Belg, 95 (1986) 29.12 Ref. 4, pp. 125,452.