Solubility analysis of homologous series of amino acids and solvation energetics in aqueous potassium sulfate solution

In this study we estimated the solubilities of glycine, D,L-alanine, D,L-nor-valine and D,L-serine in aqueous mixtures of potassium sulfate (K₂SO₄) at 298.15 K using analytical 'gravimetric method'. The experimental solubilities of homologous series of amino acids in aqueous K₂SO₄ mixture were discussed in terms of relative solubility, salting-in and salting-out effect by evaluating the influential constants. The effect of physicochemical and chemical factors on solubility were discussed briefly and correlated with the thermodynamics. Initially, the study of solvation energetics such as transfer Gibbs energies were evaluated based on the calculations from solubility data and relative stability of the experimental molecules was discussed under the experimental condition.

Polyion-counterion interactions in sodium carboxymethylcellulose-ethylene glycol-water ternary solutions

Polyion-counterion interactions in sodium carboxymethylcellulose-ethylene glycol-water ternary system have been investigated with special reference to their variations with the polyelectrolyte concentration, the medium relative permittivity and the temperature using electrical conductance measurements. The experimental data have been analyzed on the basis of a model for semidilute polyelectrolyte conductivity which takes into account the scaling arguments proposed by Dobrynin et al. Concentration-dependent moderate counterion condensation (24-33%) was observed. Counterion condensation is found to be spontaneous which depends upon the EG-content of the medium and the temperature. A major proportion of the current is transported by the carboxymethylcellulose polyions. The results further demonstrated that the monomer units experience more frictional resistance in solution as the EG-content increases or as the temperature decreases.