A simultaneous TG-DTA-MS study was made in a helium flow for an amorphous gel prepared by the addition of water to an ethanolic solution of tungsten hexachloride before evaporating the solvent at ambient temperature. Four endothermic mass losses were observed at approx. 40-80, 130-170, 190-200 and 210-600 degrees C, The first was attributed to desorption of hydrochloric acid and water, The second was attributed to the simultaneous evolution of (1) hydrogen chloride and ethylene, and (2) chloroethane. The third occurred very rapidly and was attributed to the same gases as the second loss. The fourth occurred very slowly and was attributed to the desorption of hydrogen chloride. The firing process of the gel was discussed on the basis of the decomposition mechanisms.