CrO ₂ ‐Cr ₂ O ₃ Phase Boundary Under High O ₂ Pressures

The phase boundary between CrO 2 and Cr 2 O 3 was reinvestigated under high O 2 pressures by using a new type of gas compressor. The boundary curve can be represented as log Po 2 = 7.16‐(3579/ T ). Using the observed data, Δ G °, Δ H °, and Δ S ° for the reaction 2CrO 2 ⇋Cr 2 O 3 +½O 2 were calculated to be: Δ G °= ‐(1.55/100) T +7.60 kcal/mol, Δ H °= ‐8.19 kcal/mol, and Δ S °= (‐15.8/ T )+0.0155 kcal/mol.