Vapor pressure and dissociation energy of (In₂O)

Abstract

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.