Tungsten Tetrachloride, WCl₄

By partial reduction, with hydrogen, of the hexachloride, Riche obtained this compound in the form of voluminous, greyish-brown crystals, which may be more readily obtained by distilling a mixture of the hexa- and penta-chlorides at a low temperature in a current of hydrogen or carbon dioxide. It is also formed, together with other compounds, during the preparation of the pentachloride. It is infusible, but decomposes at a moderately high temperature into pentachloride and dichloride; if sufficiently heated, the ultimate metallic residue is pyrophoric. In presence of water the compound undergoes hydrolysis.

A double hydroxychloride of tungsten with potassium chloride has been prepared by the reduction with tin of a solution of potassium tungstate in concentrated hydrochloric acid; after a series of colour changes the compound K₂W(OH)Cl₅, which is stable in the dry condition, is obtained.