Differential Thermal Analysis of Thallous Azide

Abstract

IN their review of inorganic azides, Evans, Yoffe and Gray¹ note that the crystal structure of thallium azide is body-centred tetragonal and that the compound melts with decomposition at about 334° C. On differential thermal analysis, a solid-state transition is shown before the fusion process. As shown in Fig. 1A this transition has a maximum peak temperature at 291° C. If the sample is allowed to undergo a cooling cycle before decomposition sets in, then the transition is seen to be reversible. Fig. 1A, however, takes the sample through the decomposition process. The exothermic peak is caused by oxidation of the azide group to molecular nitrogen. Thallium metal is the other product of the thermal decomposition and Fig. 1B shows the hexagonal-cubic transition near 234° C, previously reported by Maziéres², followed by melting at 299° C.