New experimental liquid-liquid-phase equilibrium data are reported for aqueous systems containing poly(vinyl pyrrolidone)sof different molecular masssand sodium sulfate at (298 and 338) K together with parameters for a semiempirical model for the excess Gibbs energy which is used to describe the experimental data.

The solubility of sodium sulfate in a mixed solvent water3methyldiethanolamine at 25 and 35oC was studied experimentally using the gravimetric method and gravimetric acid3base titration. The solubility diagrams obtained for the first time were compared with those of sodium sulfate in binary solvents mono-ethanolamine3water and diethanolamine3water.

This paper reports experimental data for the activity of water in aqueous solutions of 3-methyl-1-vinylimidazolium methyl sulfate (QVI) at (298 and 338) K and the solid−liquid equilibrium for the ternary system (QVI + sodium sulfate + water) at the same temperatures. QVI is an ionic monomer which is gaining importance as a monomer for water-soluble polymers. The experimental data presented here are to contribute to a database which is needed to develop and test thermodynamic models for the description/prediction of phase equilibrium in aqueous solutions of such polyelectrolytes. The new experimental results for the activity of water are described by the VERS model of Groβmann et al. for the excess Gibbs energy of aqueous solutions. Two interaction parameters were adjusted to correlate that data. The data set comprising the solid−liquid equilibrium was used for determining another set of interaction parameters (between that vinylimidazolium salt and sodium sulfate).

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