The system iridium ‐ oxygen I. Measurements on the volatile oxide of iridium

Abstract

Abstract It is shown experimentally that the volatility of iridium in oxygen at high temperatures is due to the formation of a volatile oxide. The dependence of the partial pressure of this gaseous oxide on the oxygen pressure (in equilibrium with iridium or IrO 2 ) was determined by a transportation method. From the results the formula of the volatile oxide of iridium appeared to be IrO 3 . The equilibria: 2 Ir (s) + 3 O 2 ⇄ 2 IrO 3(g) and 2 IrO 2(s) + O 2 ⇄ 2 IrO 3(g) were measured as a function of the temperature. The results can be expressed as: log K p (mm) = ‐ 2034/T ‐ 7.346 and log K p (mm) = ‐ 27596/T + 16.902, respectively.