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Colligative properties of polyelectrolyte solutions. IV. Activity coefficient of sodium ion

1957; Wiley; Volume: 25; Issue: 108 Linguagem: Inglês

10.1002/pol.1957.1202510806

1542-6238

Mitsuru Nagasawa, Ikumi Kagawa,

Electrostatics and Colloid Interactions

Abstract By the concurrent use of the ion exchange membrane electrode in addition to the sodium amalgam electrode, the ionic activity of sodium ion in salt‐free polyelectrolyte solutions was determined over a considerably wide range of sample concentration. As polyelectrolyte samples, several kinds of sodium polyvinyl alcohol sulfates differing in their degrees of esterification and degrees of polymerization (sodium polystyrene sulfonate, sodium cellulose sulfate, and carboxymethylcellulose) were used. The peculiar dependency of the activity coefficient of sodium ion upon the sample concentration first noted by Kern was confirmed with all samples in this study; that is, γNa + decreases with dilution of the sample solution. Further, it was confirmed that the degree of esterification, viz. , the charge density on a linear polymer, is a most important factor while the activity coefficient is entirely independent of the degree of polymerization. The influence of structure of the polymer skeleton upon the activity coefficient was found to be comparatively small. Some of the above results were discussed on the basis of the authors' theory published in a previous paper.