EXTRACTION OF WATER BY SOME ORGANOPHOSPHATES

The solubility of water was determined in tri-(2-ethylhexyl) phosphate, tri(butoxyethyl) phosphate, tri-isobutyl phosphate, diphenyl methyl phosphate, dibutyl cresyl phosphate, dicresyl butyl phosphate, and trimethyl thiophosphate at 25° and various water activities. The activity of the organophosphates was derived from the solubility, applying Gibbs-Duhem relation. The resulting values of as approximate closely as = xs, when aw at low water activities obeys Henry's law aw = H·xw. There is satisfactory agreement between Henry's law constants, as obtained from the solubility data, and the values of activity coefficients at infinite dilution derived from gas chromatography. The behaviour of the excess thermodynamic functions for the considered systems is similar to that observed in solute-water mixtures in which hydrogen bonds are formed. In addition, molar refractions and densities, as a function of temperature and water concentration, were measured.