Vapor pressure and dissociation energy of (In₂O)

The vapor pressure of pure liquid indium, and the sum of pressures of (In) and (In2O) species over the condensed phase mixture {In} + <In2O3>, contained in a silica vessel, have been measured by Knudsen effusion and Langmuir free vaporization methods in the temperatue range 600 to 950°C. Mass spectrometric studies reported in the literature show that (In) and (In2O) are the important species in the vapor phase over the {In} + <In2O3 >; mixture. The vapor pressure of (In2O) corresponding to the reaction, 4 In+<In2O3>→3(In2O) log p=−13.150—T+7.58(±0.02)atm deduced from the present measurements is given by the equation, The “apparent evaporation coefficient” for the condensed phase mixture is approximately 0.8. The energy for the dissociation (In2O) molecule into atoms calculated from the above equation is D°0 = 180.0 (± 1.0) kcal mol−1