Аннотация:It is shown that interactions in anhydrous systems KLA(SO4)2 – CaSO4 and KLA(SO4)2 – SrSO4 do not lead to the formation of new compounds and solid solutions, while in the system KLA(SO4)2•H2O – SrSO4•0,5H2O the existence of solid solution regions based on the hexagonal and first discovered rhombic modifier SrSO4• 0,5H2O is established.