Effects of an electrolyte on the activities of water and alcohol in mixtures

Abstract

(1) An air-bubbling method has been devised for the determination of the partial pressures of water and alcohol in mixtures, in which the volume of air required is less than a litre.(2) The partial vapour pressures of water and alcohol have been measured at 25°C, in mixtures containing no solute and in mixtures containing lithium chloride at concentrations of o. 5 m, 1.0 and 4.0 m. Similar measurements have been made at 35°0. with a concentration of 1.0 m and also with no solute.(3) It has been shown that, in water.alcohol mixtures, lithium chloride lowers the activity of water, while it may either lower or raise that of alcohol, depending on the composition of the solvent and the concentration of lithium chloride. The fractional lowering, in the case of water, is always greater than that in the case of alcohol.(4) An approximately linear relation has been established between the relative activities of both water and alcohol, and the molar fraction of alcohol in the solvent.(5) The latent heats of evaporation of water and alcohol in mixtures containing no electrolyte, and in mixtures with lithium chloride at a concentration of 1.0 m as solute,have been calculated, but these results do not appear to be very significant.