| The lowest oxide of vanadium which can be obtained by the reducing action of hydrogen is vanadium trioxide, V2O3. In the case of the sulphides, however, the reducing action of hydrogen appears to proceed still further, notwithstanding the fact that hydrogen sulphide is a much less stable compound at a red heat than water-vapour. By passing hydrogen over heated vanadium trisulphide, V2S3, at 1100° to 1200° C. for from four to eight days, the monosulphide, VS, has been obtained. Wedekind and Horst, however, were unable to obtain any of the sulphide by this method, but found that it resulted, more or less impure, from the action of hydrogen sulphide on hypovanadous oxide, VO. Vanadium monosulphide forms either glistening, black scales, of density 4.2, or a brownish-black, amorphous powder, density 4.4. Its magnetic susceptibility has been studied. On being heated in air it absorbs oxygen readily with formation of vanadium pentoxide and evolution of sulphur dioxide. It is attacked only very slightly by boiling hydrochloric acid, both strong and dilute, and boiling dilute sulphuric acid; hot concentrated sulphuric acid dissolves it slowly, while nitric acid, strong or dilute, attacks it readily. It is soluble in colourless ammonium sulphide, giving a purple solution, and in yellow ammonium sulphide, yielding a wine-red solution. Caustic soda and ammonium hydroxide have a slight solvent action on the sulphide. |