Densities and partial molar volumes of aqueous solutions of lithium,sodium, and potassium hydroxides up to 250°C

The densities of aqueous solutions of lithium, sodium and potassium hydroxides were measured up to 3m (mol-kg^–1) with a vibrating tube densimeter from 55 to 250°C an at pressures close to saturation. The apparent molar volumes of the solutions were calculated and the infinite dilution values at each temperature and saturation pressure were obtained by extrapolation. The present data are compared with literature values (for LiOH and KOH below 75°C and over the entire temperature range for NaOH) and with the predictions of a semiempirical model. It is concluded that the high temperature data for NaOH reported here improves the available experimental information on the volumetric properties of this system. The influence of ion association on the volumetric properties of LiOH solutions is also discussed.