Capacités calorifiques, volumes, expansibilités et compressibilités des solutions aqueuses concentrées de LiOH, NaOH et KOH

Abstract

The densities and heat capacities of various alkali hydroxides were measured in water with a vibrating tube densimeter and a flow microcalorimeter in the temperature range 4 to 55 °C. The concentration ranges investigated were respectively: 0.04 to 3.8 mol kg −1 for LiOH, 0.02 to 10.9 mol kg −1 for NaOH, and 0.02 to 15.5 mol kg −1 for KOH. The partial molar volumes [Formula: see text] and heat capacities [Formula: see text]were calculated from the least-squares fit of the apparent molar quantities [Formula: see text] as a function of molalities. From the temperature dependence of these functions the apparent molar expansibilities [Formula: see text] and [Formula: see text] were derived. The ultrasonic velocities were also measured for the dilute solutions of NaOH at 25 °C, and can be used to calculate the standard partial molar compressibilities and isochoric heat capacities. The present data were compared with literature values. The general trends as a function of concentration are similar to those of other 1:1 electrolytes even though the deviations from the Debye–Hückel theory are larger.