The System Manganese Oxide–Cr 2 O 3 in Air

The quenching technique has been used to determine equilibrium relations in the system manganese oxide‐Cr 2 O 3 in air in the temperature range 600° to 1980°C. The following isobaric invariant situations have been determined: At 910°± 5°C tetragonal Mn 3 O 4 solid solution, cubic Mn 3 O 4 solid solution (=spinel), Mn 2 O 3 solid solution, and gas coexist in equilibrium. Cubic Mn 3 O 4 solid solution, Cr 2 O 3 solid solution, liquid, and gas are present together in equilibrium at 1970°± 20°C. The invariant situation at which cubic Mn 3 O 4 solid solution, Mn 2 O 3 solid solution, Cr 2 O 3 solid solution, and gas exist together in equilibrium is below 600°C.