VAPOR PRESSURES OF AQUEOUS MELTS . LITHIUM NITRATE-POTASSIUM NITRATE-WATER AT 119-150 DEGREES

Vapor pressures of the system LiNO3-KNO3-H2O were measured in the temperature range 119-150° using a differential transpiration method. The water concentration was varied from 0.05 to 1.0 mol of H2O/mol of nitrate and the salt composition range was 0.45 to 0.70 mol of Li+/mol of nitrate. The vapor pressure varied from 47 to 338 mm and was found to be a linear function of the water mole ratio for the equimolar salt mixture. At a fixed water concentration, as the lithium ion to potassium ion ratio increases, the vapor pressure decreases in accord with the greater hydration of Li+ compared with K+. The enthalpy of vaporization of water from the equimolar salt mixture in the temperature range 119-150° is 10.4 kcal/mol compared with a value of 9.3 kcal/mol for the enthalpy of vaporization of pure water at 135°.