PHOSPHORUS DISTRIBUTION BETWEEN Na₂O-SiO₂-FeO SLAG AND CARBON-SATURATED IRON AT HOT METAL TEMPERATURES.

The equilibrium distribution of phosphorus between Na//2O-SiO//2-FeO melts and carbon-saturated iron in the soda-ash treatment process was measured at 1,300 degree C using a solid iron strip. The logarithm of the phosphate capacity of the system increases from 19. 5 to 24. 8 with increasing the basicity index (X(Na//2O) plus X(Na//2CO//3 /X(SiO//2) ) plus X(PO(2. 5) ) plus X(FeO(1. 5)) from 0. 7 to 1. 2, where X//i represent the molar fractions of bases. Iron oxide decreases the phosphate capacity of the slags. The phosphate capacity of the slag used in the soda-ash treatment is found to be very high, having the logarithm of phosphate capacity of about 31. The partial oxygen pressure at the slag-metal interface is estimated to be at 10** minus **1**5 to 10** minus **1**6, which is much lower than the process using CaO-base slag.