Solubilities and Dissolution States of a Series of Symmetrical Tetraalkylammonium Salts in Water

Abstract

The solubilities of a series of symmetrical tetraalkylammonium salts, R4NX (R=CH3–n-C8H17, including i-C4H9 and i-C5H11; X=Cl, Br, I, NO3, and ClO4), in water have been determined over the temperature range between 5 and 45 °C. The solubilities of these salts were found to be strongly dependent upon both the chain length of R of the R4N+ cation and upon the partial molar volume of the X− anion. It has been concluded that these solubilities are closely related with the stability of a “cage-like” water structure, which is presumably formed around the R4N+ cation in the solution. A thermodynamic interpretation of the solubility of the R4NX salts was made by using some thermodynamic properties obtained by a differential scanning calorimetry, together with the enthalpy of the solution calculated from the temperature dependence of the solubility.