STUDY ON PHASE-DIAGRAM OF THE NA(-), SO4(2-), H2O SYSTEM AT 100-DEGREES-C - THE FUNDAMENTAL OF UTILIZATION OF NAHCO3 MOTHER LIQUID OF NATURAL SODA BRINES BY AMMONIATION CARBONATION PROCESS(), NH4( +) CL()

The natural soda lakes in Jilin province and Inner Mongolia Autonomous region and the upper stratum of trona deposite in Henan province are composed mainly of NaHCO3, Na2CO3, NaCl and Na2SO4. After ammoniation and carbonation of their brines, a large proportion of Na2SO4, NaCl an d Na2CO3 Will be converted to NaHCO3 and precipitated out. For the pur pose of optimizing separation process of NH4Cl and Na2SO4 from the dis tilled NaHCO3 mother liguid, the phase diagram of Na+, NH4+/Cl-, SO42- , H2O system at 100-degrees-C has been studied. It is observed that th e Dawson salt can be formed at such a high temperature. This fact nega tes the conclusion drawn by Dawson and Rivett that Dawson salt can not set out at the temperature above 59.3-degrees-C.