Molybdenum trioxide, Mo03, is prepared by oxidizing the metal or the sulphide by heating them in air, or with nitric acid.
Molybdenum sesquioxide, Mo 2 O 3, a black mass insoluble in acids, is formed by heating the corresponding hydroxide in vacuo, or by digesting the trioxide with zinc and hydrochloric acid.
Molybdenum disulphide, MoS 2, is found as the mineral molybdenite, and may be prepared by heating the trioxide with sulphur or sulphuretted hydrogen.
At the same time a little trioxide is formed, and, according to Hempel (Ber., 1890, 2 3, p. 1 455), half the sulphur is converted into this oxide if the combustion be carried out in oxygen at a pressure of 40 to 50 atmospheres.
Four oxides of sulphur a.re known, namely sulphur dioxide, S02, sulphur trioxide, S03, sulphur sesquioxide, S203, and persulphuric anhydride, S 2 0 7.