Influence of temperature gradients on the composition of crystallization products of ammonium chloroplatinum(IV) and chlorohodium(III) complex salts

The influence of temperature gradients on the particle size and component composition of solid phases in heterogeneous systems of ammonium chloroplatinum(IV) and chlorhodium(III) complex salts was studied. A Benard cell was implemented as applied to not only homogeneous but also heterogeneous systems. Two contributions to the cocrystallization of rhodium with platinum are distinguishable and kinetically resolved: the formation of nonequilibrium solid solutions by ammonium chlorometalates and equilibrium Ostwald ripening. The elucidation of both factors helps in finding crystallization parameters for minimizing the rhodium contamination of platinum in refining practice.