Ion Association Ofhomologous Dicarboxylic Acids in Aqueous

Indian Journal of Chemistry Vol. 35A, November 1996, pp. 983-988

Ion association of homologous dicarboxylic was further purified by the method available in the acids in aqueous acetone solutions at literature'.Conductivity water (sp. condo "..106 s dliIerenttemperatures em -1) was used for preparing water + acetone mixtures. The acetone content in the mixed solvents was accurate to within 0.01%. The solutions of UN Dash.· & BK Mohanty ± the acids in water and water + acetone mixtures Department of Chemistry, Utkal University, Bhubaneswar 751 004 were prepared by weight and conversion of molal- ity to molarity was done by using standard expres- Received 26 March 1996; revised 27 May 1996 sion. The conductivities of oxalic, malonic, succinic, glutar- The, viscosity measurements were made in water ic and adipic acids have been measured in water and thermostat m.amtained at appropriate temperatures water+acetone (Xacetone=0.016,1,0.033, 0.072, 0-117 varying within 0.05 K by using an Ostwald type and 0.171) mixtures at 288.15, 298.15, 308.15 and viscometer fitted with a silica gel guard tube. The 318.15 K in varying ranges of concentration. The limiting molar conductance (1\0) and association constant viscometer was calibrated against conductivity wa- 3 (K A) for these acids in water + acetone mixtures are ter (10 TJ= 11.369, 8.909; 7.261 and 5.928 poise, evaluated using Shedlovsky and Fuoss-Kraus tech- d= 0.9991, 0.9970, 0.9940 and 0.9905 g mr ' at niques. The results have been discussed in terms of ion- 288.15, 298.15, 308.15 and 318.15 K respect- ion and ion-solvent interactions in these solvents. ively)", The determination of viscosity involved different solutions of the dicarboxylic acids varying from 0.01 to -0.05 molar concentrations in water and water + acetone mixtures. Runs were In an earlier work 1 we reported the effect of repeated until three successive determinations increase in chain length upon the change in were within ± 0.1 S. apparent and partial molar volume and expansi- bility of homologous dicarboxylic acids (viz.

(CH2)x(COOHh, where x=O, 1, 2, 3 and 4) in Conductance measurements", were carried out water and water + acetone (X.cetone = 0.016, 0.033, on a digital conductivity meter (Systronics, type 0.072, 0.117 and 0.171) mixtures. We now report 304) with a sensitivity of 0.1% and a dipping type the conductance values of these solutions of five conductivity cell with a platinized platinum elec- homologous dicarboxylic acids in water and wa- trode (cell constant 1 s em - l) was used. The mea- ter + acetone (Xacetone= 0.016, 0.033, 0.072, 0.117 surements were made at different temperatures and 0.171) mixtures at four different temperatures, maintained in a water thermostat as in the case of e.g. 288.15, 298.15; 308.15 and 318.15 K to exa- viscosity measurement. The experiment was re- mine the validity of Shedlovsky and Fuoss-Kraus peated several times with different concentration conductance equations. The association constants of the acids. and Walden products for these dicarboxylic acids have been evaluated in these solvents at different Results and discussion temperatures. These computed values have been The conductivity values of homologous dicar- used to discuss qualitatively the nature of the ion- boxylic acids were analysed using Shedlovsky" and solvent, solvent-solvent and ion-ion interactions of Fuoss-Kraus" extrapolation techniques. The molar the dicarboxylic acids in water and water-acetone concentration, c was derived from the molal con- mixtures. centration, m by the usual relation. Shedlovsky method involves the linear extrapo- Experimental lation using Eq. (1) Oxalic (BDH, AnalaR), malonic (E Merck, GR), succinic (BDH, AnalaR), glutaric (FlukarAG) and adipic (SRL, Pure) acids were of the same samples ... (1) as used in our earlier work'. These acids were kept in vacuum desiccator over anhydrous calcium chloride until required. Acetone (BDH, AnalaR) where 984 INDIAN J CHEM. SEC. A, NOVEMBER 1996

S(z)= 1 +z+(zZ/2)+(Z3/8) the process taking place at a definite rate which increases with temperature and 1\ °= A e - E/ RT ... (4) z=S(Ac)l!ZI Ag12 where A is the frequency factor, R is the gas con- S=aAo+b stant and E; the Arrhenius activition energy of transport processes. From the plot of In A versus a = 82.41 1](D T)112 ° 1IT for acids in water and water + acetone mix- b = 8.20 x 1Q5(DT )312 tures, the E; values have been computed from the slope of Eq. (4). and The heat of association ll.IfO obtained from the ... (2) slope of the plot of log K A versus 1I T. Free energy for the association process (ll. GO) was calculated from the equation ll. GO= - 2.303 RT log K A where a=[AS(z)]/Ao, A and Bare Debye Huck- el constants and a° is the ion size parameter. and ll.SO was calculated from the Gibbs Helm- The Fuoss-Kraus extrapolation method involves holtz equation the equation ll.SO= (ll.HO -ll. GO)I T

The values of these thermodynamic functions, F(z)1 A = ~ + (K~)( cA f ;IF(z)) ... (3) ll. GO, ll.fiO, ll.So and E, at 298.15 K are given in Ao Ao Table 2. where It is of interest to derive the value of the ratio R, defined by

R = Ao 1]0 (mixed solvent) x 1\ 1]0 (water) z and log f± are the same as defined in Eq. (1), A for the acids in water ana water + acetone mixtures. and A 0 are the molar and limiting molar conduct- The Walden product relates molar conductance at ances and K A is the association constant. infinite dilution to the viscosity (1]0) ass To start the Shedlovsky method an initial value of A 0 was obtained from the linear extrapolation 1 of A versus d12 plot. This value was used to cal- Ao 1]0 =-- 6 n r T culate the Onsagar slope (S) from the equation, S = aAo + b. Using these values of S and Ao, z, S(z) and a values were calculated as defined in Eq. (1). where r is the effective radius of the concerned ions. The values of Walden product along with The mean molar activity coefficient. f ± was deter- mined using Eq. (2). With a°= 0, q and 2q where those of r are recorded in Table 1. As observed the A 0 values obtained from Shed- q = (z + z.: EZI 2D kT ) and the symbols have their usual meanings. From the linear plot of 1/ A S(z) lovsky and Fuoss-Kraus methods are very close to each other as in our previous studies':", Unfortu- versus cAf ~ S(z), Ao and KA values were evaluat- nately the values of A derived from the more ed from the intercept (II Ao) and the slope (KAI ° A 6 respectively. The procedure was repeated us- general conductivity equation proposed by Fuoss- ing these values of A ° until there is no change in Hsia'" using Fernandez-Prini!' coefficients show a large difference from the values obtained by the the values of A ° and K A- The same procedure was applied to the Fuoss-Kraus technique foreval- former two techniques. It is therefore the A 0 values computed from the Fuoss-Hsia techniques are uating Ao and KA• All the calculations were carri- excluded from the present discussion. The A va- ed out on 486 PC XT DX computers. The Ao ° and KA values obtained by Shedlovsky method lues for the acids increase in water and wa- are recorded in Table 1 for ao = q only. ter + acetone mixtures with increase in temperature as shown in Table 1. This is due to the fact As the conductance of an ion depends on its that the increased thermal energy results in greater rate of movement it is quite reasonable 7 to treat bond breaking and variation in vibrational, rota- conductance similar to the one that employed for tional, and translational energy of the molecule

------NOTES 985

Table I-The values of limiting molar conductance Ao (s cm2mol-1), association constant KA (dm'rnol"), Walden product AolJo and effective radius r(A) obtained by Shedlovsky technique for homologous oxalic acids in water and water + acetone (X.cetone =0.016,0.033,0.072,0.117 and 0.171) mixtures at different temperatures for aO=q

Ao KA AolJo r Ao KA Ao 1J0 r

(Xacetone=0.00, T= 288.15 K) (X.cetone=0.00, T= 298.15 K) Oxalic acid 261.5 (6) 38.9(9) 2.97 6.19 296.6 (7) 55.9 (13) 2.64 6.73 Malonic acid 248.7 (9) 365.0 (56) 2.83 6.51 283.0 (7) 391.4 (61) 2.52 7.07 Succinic acid 110.2 (6) 765.7 (53) 1.25 14.70 134.0 (7) 986.1 (63) 1.19 14.91 Glutaric acid 89.8 (6) 952.4 (50) 1.02 18.05 115.2 (6) 1302.7(62) 1.01 17.34 Adipic acid 87.6(6) 1116.5 (52) 0.99 18.48 108.2 (6) 1371.9 (59) 0.96 18.47

(Xaeeton=e 0.00, T= 308.15 Kj (X.eelone=0.00, T= 318.15 K) Oxalic acid 331.5 (8) 71.4(18) 2.41 7.15 367.8 (9) 86.8 (23) 2.18 7.64 Malonic acid 320.6 (11) 427.5 (68) 2.32 7.39 359.8 (11) 465.3 (75) 2.13 7.81 Succinic acid 160.2 (7) 1236.3 (74) 1.16 14.80 188.5 (8) 1519.3 (83) 1.12 14.92 Glutaric acid 141.2 (7) 1629.7 (73) 1.01 16.08 168.9 (7)' 1963.5 (83) 1.00 16.65 Adipic acid 134.6 (6) 1814.6 (70) 0.98 17.62 162.9(7) 2163.0 (79) 0.96 17.36

(Xaeetone=0.016, T= 288.15 K) (X.cetone=0.016, T= 298.15 K)

Oxalic acid 239.9 (7) 70.5 (15) 3.14 5.86 271.7 (8) 93.8 (22) 2.65 6.71 Malonic acid 232.4 (9) 384.5 (55) 3.04 6.05 265.2 (9) 452.5 (64) 2.59 6.88 Succinic acid 106.3 (6) 845.4 (53) 1.39 13.24 126.7 (7) 1014.8 (61) 1.24 14.40 Glutaric acid 88.7(5) 1162.1 (53) 1.16 15.87 111.1 (6) 1447.0 (62) 1.08 16.42 Adipic acid 84.7(5) 1340.7 (53) 1.11 16.63 108.9 (6) 1718.3 (61) 1.06 16.77

(X.eelone=0.016, T= 308.15 K) (X.eetone=0.016, T= 318.15 K) Oxalic acid 304.3 (9) 116.5 (28) 2.36 7.28 337.4 (9) 137.8 (34) 2:04 8.17 Malonic acid 229.4 (10) 521.7 (73) 2.33 7.39 334.8 (11) 589.7 (80) 2.02 8.23 Succinic acid 146.6 (7) 1145.1 (67) 1.14 15.11 181.8 (8) 1857.9 (104) 1.09 15.22 Glutaric acid 134.3 (6) 1712.9 (70) 1.05 16.50 158.5 (7) 1965.2 (78) 0.96 17.40 Adipic acid 132.5 (6) 2174.8 (71) 1.05 16.54 154.6 (7) 2271.0 (76) 0.93 17.83

(X.eetone=0.033, T= 288.15 K) (Xaeetone=0.033, T= 298.15 K) Oxalic acid 230.8 (8) 177.1 (34) 3.33 5.52 267.7 (9) 238.1 (44) 2.90 6.14 Malonic acid 217.6 (9) 408.5 (54) 3.14 5.85 248.2 (9) 479.3 (62) 2.68 6.22 Succinic acid 85.3 (5) 815.9 (46) 1.23 14.96 106.6 (6) 1054.9 (56) 1.15 15.44 Glutaric acid 85.1 (5) 1257.5 (53) 1.23 14.99 99.4 (6) 1306.7 (57) 1.08 16.55 Adipic acid 82.8 (5) 1680'.2 (54) 1.19 15.40 95.7(6) 1886.8 (59) 1.05 17.19

(Xaeelone=0.033, T= 308.15 K) (X.eetone=0.033, T= 318.15 K) Oxalic acid 307.1 (10) 305.7 (55) 2.56 6.71 349.2(10) 378.2 (66) 2.26 7.39 Malonic acid 280.5 (10) 574.2 (71) 2.34 7.35 312.9(10) 620.6 (78) 2.02 8.25 Succinic acid 129.2 (7) 1301.4 (65) 1.08 15.95 153.1 (7) 1526.0 (73) 0.99 16.86 Glutaric acid 120.7 (6) 1522.2 (65) 1.01 17.07 146.7 (7) 1713.1 (72) 0.93 18.08 Adipic acid 113.2 (6) 2361.5 (65) 0.95 18.21 143.8 (6) 3078.0 (75) 0.91 18.46

(Xacetone=O.072, T=288.15 K) (Xacetone=0.072, T= 298.15 K) Oxalic acid 218.6 (8) 242.1 (39) 3.45 5.18 253.3 (9) 319.9 (51) 3.06 5.63 Malonic acid 205.8 (8) 441.0 (54) 3.35 5.50 233.6 (9) 522.0(62) 2.91 6.10 Succinic acid 84.8 (5) 1027.8 (49) 1.38 13.35 104.7 (6) 1261.5 (57) 1.30 13.68 Glutaric acid 83.3 (5) 1713.6 (54) 1.35 13.63 95.9(5) 1728.3 (54) 1.07 16.62 Adipic acid 78.6 (3) 2024.4(53) 1.28 14.38 90.5 (5) 2404.2 (58) 1.06 16.78 (contd)

------986 INDIAN J CHEM. SEe. A, NOVEMBER 1996

Table I-The values of limiting molar conductance Ao (s cm2mol-I), association constant KA (drn3mol-I), Walden product AoTlo and, effective radius r(A) obtained by Shedlovsky technique for homologous oxalic acids in water and water + acetone (X.celone = 0.016,0.033, 0.072, 0.117 and 0.171) mixtures at different temperatures for a" = q-Contd Ao KA AoTlo r Ao KA Ao n« r

(X.celone = 0.072, T= 308.15 K) (Xacelone=0.072, T= 318.15 K) Oxalic acid 291.5 (9) 425.3 (64) 2.76 6.02 332.0 (11) 503.6 (74) 2.46 6.77 Malonic acid 261.4 (78) 597.1 (78) 2.56 6.71 290.9(10) 975.9 (78) 2.24 7.44 Succinic acid 128.4 (6) 1610.1 (67) 1.26 13.69 148.6 (7) 1739.6 (72) 1.15 14.50 Glutaric acid 112.1 (6) 2569.7 (67) 1.09 15.79 138.6 (6) 3002.7 (76) 1.06 15.73 Adipic acid 103.3 (5) 2873.5 (65) 1.01 17.04 118.5 (6) 3314.4 (69) 0.91 18.32

(X.cetone=0.117, T=288.15 K) (Xaceton=e 0.117, T= 298.15 K) Oxalic acid 198.3 (8) 249.8 (38) 3.47 5.30 227.6 (9) 317.2 (48) 3.08 5.77 Malonic acid 192.9 (8) 484.4 (53) 3.37 5.45 219.5 (9) 566.1 (61) 2.92 6.09 Succinic acid 84.4 (5) 1284.9 (51) 1.48 12.46 99.9(6) 1391.4 (57) 1.33 13.37 Glutaric acid 79.1 (5) 2050.0 (53) 1.39 13.24 90.3 (5) 2397.0 (58) 1.20 14,82 Adipic acid 78.3 (5) 3000.8(56) 1.37 13.43 87.4 (5) 3898.9 (62) 1.15 15.47

(Xacelone=0.117, T=308.15·K) (Xacelone=0.1I7, T= 318.15K) Oxalic acid 258.4 (9) 388.8 (57) -2.80 6.14 290.1 (9) 456.6 (66) 2.49 6.69 Malonic acid 239.0 (9) 588.8 (64) 2.50 6.88 258.1 (9) 600.9 (67) 2.13 7.82 Succinic acid 123.3 (6) 1726.3 (66) 1.29 13.35 134.2 (7) 1613.8 (66) 1.11 15.02 Glutaric acid 106.4 (5) 3013.1 (64) 1.11 15.51 120.4(6) 3643.9 (71) 1.09 15.29 Adipic acid 104.7 (5) 4755.5 (68) 1.09 15.79 119.3 (6) 6331.9 (75) 0.98 17.01

(Xacetone=0.171, T=288.15 K) (Xacelone=0.171, T=298.15 K) Oxalic acid 188.6 (8) 352.6 (44) 3.24 5.68 213.4 (8) 405.9 (51) 2.80 6.35 Malonic acid 172.5 (7) 407.7 (46) 2.96 6.21 198.3 (8) 566.1 (61) 2.60 6.84 Succinic acid 81.8 (5) 1222.5 (47) 1.40 13.15 97.7 )5) 1272.1 (53) 1.28 13.90 Glutaric acid 81.6 (5) 3127.0 (56) 1.40 13.19 97.1 (5) 3869.9(61) 1.27 14.01 Adipic acid 74.4 (4) 3487.5 (55) 1.29 14.27 95.8 (5) 5064.1 (63) 1.25 14.23

(Xacelone=0.171, T=308.15K) (Xacetone= 0.171, T= 318.15 K) Oxalic acid 242.4 (9) 482.7 (60) 2.50 6.88 271.8 (9) 552.0 (68) 2.22 7.51 Malonic acid 224.3 (9) 562.9 (62) 2.31 7.45 252.2 (9) 644.5 (70) 2.06 8.09 Succinic acid 113.7 (6) 1457.1 (59) 1.18 14.58 136.1 (6) 1530.9 (64) 1.11 15.02 Glutaric acid 113.0 (5) 4789.6 (67) 1.18 14.59 134.6 (5) 5825.5 (75) 1.10 15.15 Adipic acid 111.0 (5) 7041.7 (70~ 1.15 14.79 132.2 (5) 9851.5 (77) 1.08 15.42

The figures in parentheses in Ao and KA are the standard errors with an order 10-1•

that leads to higher frequency and higher mobility may be concluded that the solvodynamic radii of of ions. As observed the A ° values in all solvents the acids take an important role for influencing decrease as we go from oxalic acid to adipic acid. the ionic mobilities and differentiation of the con- This is reasonable in view of the difference of trans- ductivities of the acids. Unfortunately it is not pos- port properties of the solvated carboxylate ions sible at present to evaluate the solvodynamic radii which reflect factors affecting their effective sizes and examine quantitatively in solutions. However, and the strength of the coulombic field in the we must emphasize that the differentiation of the range of solvation shell. The factors which influ- conductivity of the acids investigated can be most ence the sizes of the carboxylic acids can be radii probably accounted for by the extent of ion-solva- of the non solvated carboxylate ions and the inte- tion and the ion-pair association. rionic distance between H+ and carboxylate ion. Association constant K A was computed from Both these factors influence the solvodynamic ra- Shedlovsky method taking a? = q as shown in dii of the ions and influence A ° .values. Thus it Table 1. As observed the values of K A increase NOTES 987

Table 2-Thermodynamic parameters 6.Gu (kJ mol-I), 6.Hu (kJ rnol : '), 6.Su (kJ mol-IK-I), E, (kI mol-I) for homologous oxalic acids in water and water + acetone (X,celone=0.016, 0.033, 0.072, 0.117 and 0.171) mixtures at 298.15 K 6. GU 6.HO 1036. SU E, 6. GO 6.HO 1036. SO E, (X.cetone=0.00) (X.cetone= 0.016) Oxalic acid -10.01 (5) 20.21 (71) 101.03 (4) 8.74(4) -11.29(6) 17.04(67) 94.82 (4) 8.63 (4) Malonic acid -14.83 (4) 6.23 (32) 70.74 (3) 8.44(3) -15.19(2) 10.97 (55) 87.66 (5) 9.24(5) Succinic acid -17.20 (2) 17.36 (68) 115.61 (6) 13.59 (5) - 17.19 (3) 18.74(70) 120.70 (6) 13.21 (5) Glutaric acid - 17.81 (2) 18.27 (69) 120.42 (7) 15.96 (6) -17.51 (2) 13.34 (61) 97.10 (5) 14.73 (6) Adipic acid -17.95 (1) 17.26 (59) 118.22 (6) 15.89(6)- 18.53 (3) 14.27 (63) 109.79 (6) 15.55 (7)

(X.cetone = 0.033) (X.cetone = 0.072) Oxalic acid -13.61 (4) 19.33 (68) 110.20 (6) 10.47 (5) - 15.56 (4) 18.97 (68) 111.78 (5) 10.60 (5) Malonic acid - 15.35 (3) 11.04 (49) 88.50 (5) 9.19(4) - 15.58 (3) 10.85 (53) 88.58 (5) 8.71 (4) Succinic acid - 17.29 (2) 16.15 (64) 112.04 (6) 14.80 (6) -17.74 )1) 13.55 (58) 106.42 (6) 14.34 (6) Glutaric acid - 17.82 (2) 6.32 (28) 81.64 (6) 13.24 (6) - 18.56 (I) 17.85 (52) 110.59 (5) 13.53 (6) Adipic acid -18.73 (1) 17.85 (66) 117.16 (7) 13.80 (6) -19.34(1) 12.70 (45) 107.57 (5) 10.35 (5)

(X.cetone = 0.117) (X.cetone = 0.171) Oxalic acid - 14.35 (5) 15.91 (59) 101.39 (7) 9.64(4) -14.98 (3) 11.58 (38) 89.26 (6) 9.32 (4) Malonic acid - 15.81 (3) 5.29 (23) 70.37 (5) 7.17 (3) - 15.43 (3) 11.56 (36) 90.50 (6) 9.59(6) , Succinic acid -17.20(1) 6.98 (29) 84.00 (6) 12.92 (3) -17.81 (I) 6.16 (27) 80.68 (5) 11.88 (6) Glutaric acid -19.35 (1) 13.45 (68) 110.15 (8) 10.68 (0) - 20.56 (I) 15.82 (63) 122.11 (6) 12.76 (7) Adipic acid -20.55 (1) 20.88 (78) i3 t.36 (9) 13.76 (7) -21.23 (1) 26.20(81) 159.05 (7) 18.07 (8)

The figures in parentheses in 6. GO, 6. HO, 103 6. So and E, are the standard ';rrors with an order 10-2

with increase in temperature in all solvents. As ex- Xacelot1c= 0.117. This may be owing to characteris- pected the values of K A increase with increase in tic structural changes of water with addition of acetone content of the solvent. Our investigation acetone. The addition of acetone increases the 3D of the acids show a considerable ion pair associa- polymeric structure of water and the structure for- tion. A larger ion pair association of adipic acid in mation increases and continues to about Xacetone Xacetone= 0.171 can be attributed to less anion sta- = 0.117. In this case the structure formation means bility and to the lack of solvation of the ion. The that 3D-polymeric structure of water breaks and

increase in K A from oxalic acid to adipic acid in formation of possible CH3COCH3, H20 complex all solvents can be interpreted in terms of the ef- structure appears. The observed increase in Wald- fect of the anion on the structure of the solutions. en product with increase in acetone contents in The increase in association constant for a particu- the solution about Xacetone=0.117 may be due to lar acid on passing from water to water + acetone the fact that (he effective ionic radii decrease with mixtures and with increase in temperature is due increase in acetone content. It is seen that R, va- to different extent of the association of the ions in Iue increases with increase in acetone content but solutions and different extent of ion solvation in decreases with rise in temperature. This may be solutions. In both Shedlovsky and Fuoss-Kraus, due to the fact that the solvation of ions is by the techniques the values of KA for a? = 0, q and 2q acetone molecules in these mixed solvents. Such a decreases from a? = 0 to a? = 2q. Taking the devia- fact is also observed by Kalidas et alp·l3. The tion in the obtained A 0 and K A values into con- smaller AorJo value (Table 1) for adipic acid may sideration on the whole, it could be concluded be due to its large effective radius of its ions that the Shedlovsky technique is superior to the whereas oxalic acid with larger AorJo value pos- Fuoss-Kraus method. sesses a smaller effective radius. The Walden product (Ao rJo) values decrease As observed (Table 2) the values of d HO and from oxalic acid to adipic acid in all solvents, so d S° are positive for all the acids in all solvents. solvation effects are reflected in the variation of This indicates that the association process is en- Walden product of the acids. As observed the dothermic in nature and more energy consuming. Walden product value for all the acids increases This is consistent with the positive E, values of all and passes through a maximum in the region acids in solvents. 988 INDIANJ CHEM. SEe. A, NOVEMBER 1996

References 6 Fuoss RM, J phys Chem, 79 (1975) 525, 1983; 81 (1977) 1 Dash U N & Mohanty BK, Indian J Chern, 35A (1996) 1829. 188. 7 Glasstone S, An introduction to electrochemistry (van Nos- trand, New York) 1965. 2 Bruno P & Della Monica M, J phys Chern, 76 (1972) 8 Bhat J 1& Bindu P, J chern Soc, 72 (1995)788. 3034. 9 Dash U N & Supkar S, Proc Indian Acad Sci (Chern Sci) 3 Levit B P (Ed) Findlays practical physical chemistry, 9th 107(5)(1995) 541. Edn (1973) Longman. London 10 Fuoss RM & Hsla KL, Proc Natl Acad Sci USA, 57 4 (a) Dash U N & Pattanaik E R, Indian J Chern, 34A (1966) 1550;58(1967)1818. (1995)556. II Fernandez-Prini R, Trans Faraday Soc. 65 (1969) 3311. (b) Dash U N & Pattnaik E R, Bulletin of Electrochem, 7 12 Zanardhan S & Kalidas e. Rev inorg Chern, 6 (1984) 101. (1995) 11. 13 Sree Kumar T K, Rajendra G & Kalidas C, Indian J 5 Shedlovsky T & Kay R L, J phys Chem, 60 (1956) 151. Chem, 31A (1992) 782.