Gibbs Transfer Energies of Some Uni-Univalent Salts in Water—N-Methyl-2-Pyrrolidinone Solvent Mixtures at 30°C

The standard Gibbs transfer energies of some uni-univalent electrolytes like potassium picrate, tetraphenylarsonium picrate, potassium and silver tetraphenyl borate were determined in water + N-Methyl-2-Pyrrolidinone mixtures from solubility measurements at 30 °C. They were split into respective ionic values on the basis of the reference electrolyte method using tetraphenylarsonium tetraphenylborate. The variation of transfer energies of the ions with composition of solvent are examined and discussed in terms of the possible ion-solvent interactions.

Gibbs Transfer Energies and Solvent Transport Numbers of Some Copper(II) Salts in Methanol-Dimethylformamide Mixtures

Standard Gibbs energies of transfer have been determined for copper(II) iodate, benzoate and formate at 30°C in methanol- dimethylformamide mixtures by solubility measurements. Single-ion transfer energies were obtained by using the negligible liquid junction potential assumption, along with relevant literature data, and are in excellent agreement with values estimated from the reference electrolyte ( tatb ) assumption. The results obtained indicate that all of these salts are heteroselectively solvated in these mixtures, with Cu2+ being preferentially solvated by dmf and the anions by MeOH. This model is consistent with calculations based on the quasi-lattice quasi-chemical theory of Marcus and with solvent transport numbers obtained from e.m.f . measurements.

Ion-Solvent Interactions of Zinc(II) Salts in Water- Pyridine Mixtures

The ion-solvent interactions involving zinc(II) salts viz. iodate, fluoride and benzoate in waterpyridine mixtures have been investigated by solubility and solvent transport number measurements. The standard Gibbs transfer energies of the salts (Δ Gtº), determined from their saturation solubilities in the solvent mixtures, decrease up to xpy = 0.1 for zinc(II) iodate, but up to Xpy = 0.4 for zinc(II) benzoate, and subsequently increase with the addition of pyridine. For zinc(II) fluoride, however, a continuous increase of ΔGtº with the addition of pyridine is observed. The transfer energy of Zn2 + is negative and that of anions is positive with the former decreasing and the latter increasing continuously with the addition of pyridine. The solvent transport number of pyridine (<Δpy) is positive and passes through a maximum for all the salts in the range xpy = 0.25 to 0.55. These results indicate a heteroselective solvation of the salts with Zn2 + being preferentially solvated by pyridine and the anions by water