Solubilization of water in non-polar solvents by cationic detergents

Solubilization of water in common organic solvents by fatty acid salts of long-chain (C$_{12}$$\chembond{1,0} $C$_{18}$ aliphatic primary amines was studied. It was found that, of all the salts from formate to palmitate and oleate, dodecylamine-n-butyrate and octadecylamine propionate solubilize most in xylene, the figure reaching about 29 molecules of H$_{2}$O/mole of soap. Additions of free amine enhanced solubilization, while free butyric acid decreased the intake. Our viscosity and freezing-point measurements of the same systems indicated that the additive is most likely to form a complex with soap micelles, and that their solubilizing power is modified thereby. Freezing-point measurements of detergent solutions with and without the solubilized phase showed, surprisingly enough, that the dissolved water elevates the freezing-points considerably, showing that solubilized water acts as a binding agent between micelles and probably promotes micelle formation. The results are discussed and correlated on Winsor's theory of solubilization.