caa a22 4500 37887375X CHVBK 20180305123415.0 cr unu---uuuuu 161128e20031101xx s 000 0 eng 10.1524/zpch.217.11.1341.20486 doi (NATIONALLICENCE)gruyter-10.1524/zpch.217.11.1341.20486 Ion-Solvent Interactions and Determination of Single-Ion Gibbs Energies of Transfer from the Studies of the Solubility and Dissociation Constants of Oxalic Acid in Aquo + Methanolic Mixtures [Elektronische Daten] [S. K. Gumtya, S. C. Lahiri] The solvent effects on the dissociation of the simplest dibasic organic acid were examined from the determination of the first and second dissociation constants of oxalic acid conductometrically and pH-metrically in water + methanol mixtures (0-87 wt% of methanol). The solubility values of oxalic acid and potassium hydrogen oxalate were also determined in water + methanol mixtures. The dissociation constant and the solubility values were used to calculate the Gibbs energies of transfer ΔG0t of oxalic acid (H2OX), bioxalate (HOX−), oxalate (OX2−) and potassium (K+) ions from water to aquo-methanolic mixtures. These represent the quantitative measures of solute or ion–solvent interactions of the respective species in going from water to methanol + water mixtures. pK1, pK2 and the solubility values of oxalic acid increase continuously with increase in organic co-solvent. ΔG0t(H2OX) and ΔG0t(H+) are negative i.e. favourable but ΔG0t(H2OX), ΔG0t(OX2−) and ΔG0t(K+) are in general positive and hence unfavourable for the dissociation processes. The increase in basicity fecilitated the dissociation processes but decrease in dielectric constant and H-bonding capability enhance the association processes as the organic co-solvent increases. Attempts have been made to understand the solvation processes in terms of the structure of the aquo + organic mixtures and Walden products. The pK values can be suitably utilised to prepare buffer solutions in methanol + water mixtures. The solvent effect and solvation phenomena can be better understood from the collection of single-ion values of transfer. These may be utilised to calculate the solubilities of electrolytes in methanol + water mixtures. © 2003 Oldenbourg Wissenschaftsverlag GmbH Thermodynamics & statistical physics nationallicence Laboratory techniques, experiments nationallicence Physical chemistry nationallicence Gumtya S. K. aut Lahiri S. C. aut Zeitschrift für Physikalische Chemie/International journal of research in physical chemistry and chemical physics Oldenbourg Wissenschaftsverlag GmbH 217/11/2003(2003-11-01), 1341-1360 0044-3336 217:11/2003<1341 2003 217 zpch https://doi.org/10.1524/zpch.217.11.1341.20486 text/html Onlinezugriff via DOI 1 research article jats NATIONALLICENCE 856 40 https://doi.org/10.1524/zpch.217.11.1341.20486 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Gumtya S. K. aut NATIONALLICENCE 700 1- Lahiri S. C. aut NATIONALLICENCE 773 0- Zeitschrift für Physikalische Chemie/International journal of research in physical chemistry and chemical physics Oldenbourg Wissenschaftsverlag GmbH 217/11/2003(2003-11-01), 1341-1360 0044-3336 217:11/2003<1341 2003 217 zpch CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-gruyter