Thionyl chlorie is routinely shipped in galvanized drums. The compatibility of this drum for the storage of a mixture of thionyl chloride and ethyl acetate was investigated by thermochemical studies, condensed phase and off gas analysis. The chemical incompatibility of the ternary mixtures (thionyl chloride/ethyl acetate/zinc) resulted in an exothermic runaway reaction with extensive gas evolution, which has not been heretofore described in the literature. Storage in a drum was simulated in a half-liter, high pressure containment vessel. Adiabatic calorimeter data are also presented to illustrate the mass transfer process involved in the induction period and the runaway reaction characteristics. Ethyl acetate is inert with thionyl chloride. However, in the presence of metallic zinc, an equimolar amount of each component are consumed by the reaction to generate ethyl chloride (g), sulfur dioxide (g), acetyl chloride (l) and sulfur (s). It was also found that the rate of gas evolution is highly dependent on the molar ratio of the thionyl chloride or ethyl acetate to metallic zinc in the solution. Based on the semi-batch process experiments, the reaction mechanism is proposed. A potential hazard indication based on the oxygen balance for the reaction mixture is also discussed. Data on similar ternary mixtures are presented.