Thermal Decomposition of Hydrogen Peroxide in the Vapour Phase

Abstract

Baker and Ouellet¹ reported that when they boiled 98 per cent hydrogen peroxide solution at 100° C. and passed the vapour at pressures varying between 3 and 18 cm. of mercury through a wide Pyrextube heated to 335° C., they got no explosion even when they passed an electric discharge along the tube or caused a piece of cotton to burn in the gas. We find that, in a 3-cm. diameter Pyrexâtube at 100° C., thermal decomposition flames and explosions are very readily initiated by a hot wire or a spark when the pressure is about 2 cm. of mercury or higher. At atmospheric pressure the explosion is very violent and is initiated by catalytic spots on imperfectly cleaned glass. The minimum temperature to which a wire must be heated to cause immediate ignition of the gas at atmospheric pressure has been roughly determined to be about 600° C. Thus, hydrogen peroxide seems similar in its behaviour in the vapour phase to the di-alkyl peroxides with which Harris² obtained thermal explosions. These compounds, unlike hydrogen peroxide, decompose entirely homogeneously below 170° C., the temperature around which the explosions occur. The results of the latest workers with hydrogen peroxide are not in complete agreement on this point. Giguére³ reports no slow thermal decomposition at temperatures as high as 420° C.; but Mackenzie and Ritchie⁴ are of the opinion that their results may indicate an appreciable gas-phase reaction in the upper part of their temperature range (namely, 82–137° C.).