THE THERMAL EXPLOSION OF LEAD AZIDE

Abstract

The minimum explosion temperatures for service and dextrin azides (about 315 °C. and 275 °C., respectively) are increased considerably by increase of surface: volume ratio of the container and by compressing or wetting the charge with dibutyl phthalate before explosion. When wetted, the two azides were found to be similar in respect of minimum explosion temperatures and induction periods prior to explosion. Sensitization of service azide by preheating was found to be permanent. A limit to sensitization below the minimum explosion temperature was observed, and probably exists also for sensitization above this temperature. Wetting the charge with phthalate nullifies the sensitization. Although dextrin azide alone is more thermally sensitive than service azide, mixtures of the two containing 70% or more service azide show a sharp change to service azide properties; the mixtures apparently are not exploded by the dextrin azide they contain. The value of E in the expression [Formula: see text] + constant, where t is the induction period, has been determined for both the initial and final stages of reaction preceding explosion and found to be essentially unaltered. Minimum explosion temperature of single large crystals was shown to increase with crystal size. The data are interpreted as showing that the thermal explosion of lead azide may result from self-heating, the heat of the pre-explosion reaction not being sufficiently dissipated from the material.