Abstract: Brine in Kunteyi Salt Lake belongs to Sub-type magnesium sulfate,and carnallite made from Kunteyi Salt Lake brine contains magnesium sulfate,which affects the process of decomposition of carnallite by adding water.Therefore,it is very necessary to research decomposition process of this kind of carnallite.Most intuitive index for carnallite decomposition is completely decomposition of carnallite.Taking mineral-thermostatic-cold-decomposition experimental method,using analysis of components in liquid phase and it′s coexisting solid phase，and through the analysis of four interrelated indexes that contents of K⁺ and Mg²⁺in the liquid,amount-of-substance ratio of Mg²⁺ and SO^2-₄ in solid phase and phase diagram,an accurate,and convenient method for making sure the conditions of carnallite decomposition was obtained.This method pointed out that the use of Mg²⁺ or K⁺ in liquid phase as judging-index is reasonable,reliable,and practicable.By this method the best amount of water-adding,and the most reasonable resolving-time could be achieved.

Key words: carnallite, decomposition；water-adding quantity