Heat capacities of concentrated aqueous alkaline aluminate solutions at 25°C

Magalhães, M.C.F., Königsberger, E., May, P.M. and Hefter, G. (2002) Heat capacities of concentrated aqueous alkaline aluminate solutions at 25°C. Journal of Chemical and Engineering Data, 47 (4). pp. 960-963.

Abstract

Heat capacities of aqueous NaOH/NaAl(OH)4 solutions at total stoichiometric ionic strengths of up to 6 mol kg-1 and with up to 60 mol% substitution of OH- by Al(OH)4- have been measured at 25°C using a Picker flow calorimeter. The mean apparent molar heat capacities (Cpφ) of the NaOH/NaAl(OH)4 mixtures were linear with respect to Al(OH)4- substitution, consistent with Young's rule. This enabled Cpφ values to be derived for the hypothetical pure NaAl(OH)4(aq) solutions. The results so obtained are well described by a Pitzer model adapted from the literature, even up to high concentrations.