Sodium tellurides

Davy prepared sodium monotelluride, Na₂Te, by the direct union of sodium and tellurium, and also by reduction with carbon of mixtures of an alkali-metal carbonate and tellurium oxide. In the neighbourhood of 250° C., sodium and tellurium unite with explosive violence to form the monotelluride. When the combination takes place in an inert atmosphere, the product has a bronze colour and a crystalline fracture. When dissolved in water in absence of air, it yields hydrated, acieular crystals, soluble at 40° C. in their own water of crystallization. When excess of tellurium has been employed in the preparation of the monotelluride, the mother-liquor of the crystals contains sodium and tellurium in the proportion Na₄Te₃. Isolation of this substance in crystalline form is prevented by its decomposition during evaporation, the crystalline monotelluride and free tellurium being obtained. By the action of tellurium on a solution of sodium in liquid ammonia, Hugot prepared sodium monotelluride, Na₂Te, and sodium tritelluride, Na₂Te₃. The monotelluride can also be produced by the action of tellurium on sodium hyposulphite, Na₂S₂O₄. In a current of hydrogen at 250° C., sodium and tellurium unite with explosive energy, forming the monotelluride, a colourless crystalline substance, soluble in water. It reduces auric chloride and platinum chloride to the corresponding metal, forming tellurium tetrachloride, TeCl₄. Its solution dissolves tellurium, yielding a polytelluride of the formula Na₄Te₃. From the results of thermal analysis, Pellini and Quercigh infer the existence of two other polytellurides, with the formulae Na₃Te₂ and Na₃Te₇.