Metastable Phase Equilibrium of a Ternary System of K~+,Mg~(2+)/B_4O_7~(2-)-H_2O at 25°C

摘要

The isothermal solubility of the ternary system K~+,Mg~(2+)/B_4O_7~(2-)-H_2O at 25?C has been studied and the phase diagram is determined. The results show that the system is of the simple eutonic type and can be in metastable equilibrium state within 8-16 hours. The phase diagram consists of two solubility branches corresponding to the crystallization areas of K_2B_4O_7?4H_2O and MgB_4O_7?9H_2O. The composition of the eutonic point is MgB_4O_7,0.5279%(Wt%) and K_2B_4O_7,13.9629%(Wt%) respectively. The replicate experiments proved that the phase transformation of hungtsaoite (MgB_4O_7?9H_2O) occurs after a 20 hours epuilibrium.