Pt has relatively less affinity to oxygen compared to other Pt-group metals, but it generates an oxide film by heating for 1 week with oxygen at 520℃. This can be removed by high-temperature heating or hydrogen reduction. In the meanwhile, Rh is converted to RhO by heating with oxygen or air at 600~1000℃ and gradually changed to a mixture of Rh2O3 and Rh.
The color of Rh is changed gradually to be black and green at 600~700℃, to be purple at 900~1000℃, and finally be a gray over than 1150℃ due to heat degradation of oxide.

It is double for Rh that the vaporizing amount of Pt in the air at 1300℃, 1/3 of Pd, 1/13 of Ir, and 1/100 of Ru, and it becomes decrease by progressing vacuum. The vaporizing amount is very tiny under nitrogen gas and also measurelessly little under the condition of hydrogen.
From these, it is proved that Pt is well vaporized with the oxygen.
The vaporizing amount of Pt under the oxygen is 5 folds to that of air, and 2 folds for 760mmHg to that of 25 mmHg.