An Experimental Study on Picromerite Equilkibrium in the Five—Component Brine System K—Na—Mg—Cl—SO4—H2O

This paper presents the results of experiments on the physicochemical conditions for the formation of picaromerite in the five-component brine system K-Na-Mg-Cl-SO4-H2O and the process of isothermal evaporation-crystallization of picromerite from brines.The metastable phase fields of picromerite at 15,10 and 5℃and its stable equilibrium phase field at -5℃ have been established.In addition,the phase equilibrium relationships have also been established for other salt minerals.The lower limit of formation temperature of picromerite has been deduced on the basis of experi-mental results.The isothermal evaporation crystallization path of the invariant assemblage(point D) of picromerite,epsomite,sylvite and halite at 25,15,10 and 5℃ has been revealed.Furthermore,some controversial problems are approached concerning the 25℃“solar” diagram and the 25℃ metastable phase diagram of this system.