Based on comparative analysis on solubility phase diagrams of ternary systems M_2SO_4-ZnSO_4-H_2O(M=K,Na,NH4)concerned in zinc hydrometallurgical process,it is revealed that double salts((NH_4)_2SO_4·ZnSO_4·6H_2O(s),Na_2SO_4 ·ZnSO_4·4H_2O(s),and K_2SO_4 ·ZnSO_4·6H_2O(s))are much easier to precipitate from electrolyte solutions than their single salts(NH_4)_2SO_4,Na_2SO_4,K_2SO_4,and ZnSO_4·6H_2O(s).Drops of solubility of these salts(-hydrates)with decreasing temperature can cause scaling on wall of pipelines.Lower solub...