THE SYSTEM MAGNESIUM OXIDE‐BORIC OXIDE*

Abstract

A bstract Equilibrium In the system has been investigated for compositions from 0.6 to 75 weight per cent MgO. Three intermediate compounds are present. MgO⋅B 2 O 3 melts incongruently at 988°C. to form 2MgO⋅B 2 O 3 and a liquid containing more than 99% B 2 O 3 . The other two compounds melt congruently: 2MgO⋅B 2 O 3 at 1340°C. and 3MgO⋅‐B 2 O 3 at 1366°C. At 1142°C., a region of liquid immiscibility extends from 0.6 to 36.0% MgO. Temperatures are accurate within =5°C. Conflicts between these results and those of Toropov and Konovalov (see footnote 8) are discussed.