Dissolution d'une solution solide : étude théorique et expérimentale

Abstract

From a discussion of the equilibrium conditions of a water-solid solution system and the notion of congruent dissolution, we propose two different ways of reaching stable equilibrium. We first assume congruent dissolution of the initial solid : A B1-x Cx → A- + (l-x) B+ + xC+ and the reprecipitation of a new solid phase following the partition relation between water and precipitate : |AC|/|AB| = D|C+|/|B+| where |AC| and |AB| are the concentration of the two end members in the precipitate, |C+| and |B+| ion activities in solution and D the partition coefficient. The first model is based on instantaneous equilibrium between water and precipitate, the second is a kinetic approach. Both tend towards thermodynamic equilibrium between water and the solid-solution. We have applied these models to experimental results obtained in the laboratory.