Non-isothermal dissolution of a solid particle in liquid

Abstract

The behaviour of the non-isothermal dissolution of a solid particle in liquid is modelled theoretically. It is assumed that the diffusion of solute molecules to the bulk liquid phase is the rate-determining step. For the dissolution of hexamethylenetetramine in water (ΔH=–34.14 cal g^–1), depending upon the width of the diffusion layer, the maximal temperature increase at the solid/liquid interface is ca. 0.2–1.1 °C, and for the dissolution of urea in water (ΔH= 60 cal g^–1) the maximal temperature decrease at the solid/liquid interface is ca. 0.5–2.0 °C. The difference between the temperature at the solid/liquid interface and that of the bulk liquid phase is ca.± 0.5 °C for most of the period of dissolution. For the dissolution of non-dissociating substances in water, if the temperature of the liquid phase remains constant, the heat released during the course of dissolution has a negligible effect on the dissolution behaviour. In some cases, however, solving the governing equation for the resolution of the exact temperature profile is necessary.