Isopiestic vapor pressure comparison

Abstract. Isopiestic vapor pressure comparison measurements were performed with aqueous mixtures of sodium chloride (B) with sodium polystyrenesulfonate, NaPSS, (C) and with polyvinylbenzyltri-methyl ammonium chloride, PVR4NCI, (C) to determine molal osmotic coefficients, for typical strong electrolyte-strong polyelectrolyte systems. The McKay-Perring method was applied to compute the stoichiometric mean molal activity coefficients, yn, of NaCl and y c of NaPSS or PVR4NCI, respectively, in the mixtures as a function of the osmolal concentration, m, and of the osmolal fraction of polyelectrolyte, yc. 

I now wish to report new measurements on the osmotic properties of aqueous strong electrolyte-strong polyelectrolyte mixtures conducted using the isopiestic vapor pressure comparison technique. [12] This method for determining osmotic coefficients is not as sensitive as the membrane osmometer, but it is much more accurate. It is not... 

Fig. 1. Gravimetric isopiestic vapor pressure comparison apparatus.

A great deal of information on activities of electrolytes also has been obtained by the isopiestic method, in which a comparison is made of the concentrations of two solutions with equal solvent vapor pressure. The principles of this method were discussed in Section 17.5. 

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