Properties of organic-water mixtures. IV. The effect of various salts on the miscibility gap of the glycerol triacetate-water system

Abstract

The effect of various salts on the miscibility gap of the glycerol triacetate (GTA)water system was examined at 25°C. Whereas addition of NaCl and KC1 reduces the mutual solubility of GTA and water, the addition of certain other salts, e.g., perchlorates, thiocyanates, iodides, bromides, salicylates, and zinc chloride, increases the mutual solubility of GTA and water to such an extent that complete miscibility may result.

For the anions listed the “salting-in” effects are, in general, insensitive to the cation used or its charge. Plots of equivalents of salt required to produce miscibility vs. wt. percent GTA showed curves with maxima usually at about 40% GTA. Miscibility at the maximum required ca. 1 mole of perchlorate or salicylate ions per kilogram of solvent; for thiocyanates, iodides, bromides, and zinc chloride, the corresponding concentrations were usually larger.

For several salts measurements were made in the temperature range 2° to 75°C. The mutual solubility of GTA and water in the absence of salts increases slightly with increasing temperature. Less NaC₇H₅O₃ was required for miscibility at a higher temperature. However, for Mg(ClO₄)₂, KCNS, NaI, and CdBr₂, more salt was required for miscibility at a higher temperature.