Standard free energies [Formula: see text] and entropies [Formula: see text] of transfer of glycine (G), diglycine (DG), and triglycine (TG), from water to aqueous mixtures of glycerol (GL) and urea (UH) have been determined from solubility measurements at different temperatures. This was also extended to an ionic cosolvent system like aqueous sodium nitrate solutions for G and DG. The observed [Formula: see text] and [Formula: see text]–composition profiles, as well as those obtained after correcting for the "cavity effect" as estimated by scaled particle theory (SPT), were examined in the light of various interactions. The corrected [Formula: see text]and [Formula: see text] values show a regular function of the peptide chain length of the amino acids and impart useful information regarding the involved relative structural effects of these ionic and non-ionic cosolvents.

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The protonatioddeprotonation constants for uracil (U) (pK, and pK2), thymine (T) (pK1) and cytosine (C) (pK1 and pK2) in water have been determined from emf measurements of Harned-Ehler type cells comprising HZ and Ag-AgI electrodes at five equidistant temperatures ranging from 15-35°C. The pKa values were fitted in the temperature equation pK, = AT-' + B + CT by the method of least squares and the standard free energies (AGO), entropies (AS0), and enthalpies (AH0) of protonatioddeprotonation processes in water were evaluated using the values of the coefficients A, B, and C of the respective acids. The second step deprotonation constant for T was determined using precise spectrophotometric method. The results have been duly compared with the existing literature data and are also shown to derive important reflections on the sites of protonatioddeprotonation in the light of pK values of some acids and bases of comparable~functional groups and especially the entropies of protonatioddeprotonation of the key DNA-RNA base molecules.

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Free energies (ΔGt0) and entropies (ΔSt0) of transfer at 25 °C of the nonelectrolyte p-nitroaniline from water to various alcohol + water mixtures have been determined from solubility measurements at seven temperatures from 10–40 °C. Increasing specific solute–solvent interactions have been proposed to interpret the nature of the ΔGt0-composition profiles and the enhanced structure of water in the water-rich mixed solvents has been correlated with maxima in the ΔSt0-composition profiles. The effectiveness of p-nitroaniline as a useful probe for studying solvent structure has been pointed out.