Disproportionation and Vaporization of Solid Silicon Monoxide

The vaporization rate of solid SiO was studied in the temperature range 1005° to 1475°C. It was concluded that ( a ) in an argon atmosphere the vaporization rate is external gas diffusion controlled; ( b ) only the upper layers of the charge contribute to the vaporization, so that a zero-order process is observed; ( c ) the heat of vaporization of SiO is 72.5 kcal/mole. Solid SiO disproportionates when heated in the temperature range 1000° to 1440°C, but the reaction does not go to completion. The reaction in the solid state is irreversible. The product silicon inhibits the reaction.