The solubility of CoCl2 in molten NaCl-AlCl3 was determined by aliquot sampling at 255 degrees C for acidic and basic solvent compositions. There was a pronounced compositional dependence of the solubility with a minimum at approximately the equimolar solvent composition. The solubility minimum was 1.04 x 10(-4) mol fraction of CoCl2. The solubility in the highly ordered NaCl-AlCl3 solutions was described in chemical terms. The true solubility product for CoCl2 was calculated as 1.50 x 10(-15) In basic and in somewhat acidic melts, the solubility was primarily related to the formation of the associated ionic species CoCl+, CoCl2, CoCl3-, and CoCl42-. The calculated formation constant of CoCl+ was 9.48 x 10(6), Furthermore, the specific bond free energy for the associated complex, CoCl+, was -64.43 kJ mol(-1) for a coordination number of four.