Study of processes taking place during calcination of CdS with NaCl

Formation of CdCl2 during calcination of a CdS-NaCl mixture is shown to be the result of an exchange reaction between NaCl and CdSO4 which is present in the system as an impurity or is formed upon oxidation of CdS. Small amounts of cadmium sulphate coprecipitated with CdS decrease the temperature of formation of CdCl2 and facilities formation of ZnS-CdS luminophors, if the concentration of the melting additive is sufficiently high to prevent CdSO4 from decomposing. Interaction between NaCl and CdSO4 is possible even in the course of preparation of the stock. Uniform distribution of luminescence centres in ZnS-CdS is attained in the case where formation of CdCl2 and ZnCl2 and their diffusion through intergrain surfaces and dislocations precede recrystallization of sulphides