Study of the K2Ni(SO4)2 ∙ 6H2O–K2Co(SO4)2 ∙ 6H2O–H2O diagram and determination of the conditions for growing K2(Ni,Co)(SO4)2 ∙ 6H2O mixed crystals

The phase diagram of the K2Ni(SO4)2 · 6H2O–K2Co(SO4)2 · 6H2O–H2O ternary system is investigated in the temperature range of 30–70°С, and a relationship between the compositions of the equilibrium phases of the K2Co x Ni(1–x)(SO4)2 · 6H2O (KCNSH) solid solution and the growth solution is established. It is shown how the salt compositions of the liquid and solid phases change during crystal growth upon slow cooling of solution. A dependence of the lattice parameters of the KCNSH solid solution on the concentration of isomorphic components is experimentally found.