Molybdenum trioxide MoO

Molybdenum trioxide, MoO, is a yellow-white substance made by Toasting molybdenite. It dissolves in alkalis to produce molybdates. 

Baker et al. (80) and Lutz and Masters (81) also used combustion in oxygen to determine carbon in molybdenum by photon activation analysis. The former ignited the samples directly, without any additions. The latter used lead to prevent the distillation of molybdenum trioxide (MoO ). 

Molybdenum trioxide (MoO ), cobalt nitrate (Co(NO )2.6H20), nickel nitrate (Ni(N0j>2.6H20, thioacetamide (CH3CSNH2), urea NH2CONH2), (all from LOBA Chemie), nitric acid (BDH), cyclohexene (Fluka), thiophene (Kodak) were all of analytical reagent grade. (Harshaw, S.A. 234 m g, P.V., 0.65 ml g ). 

Chemical products are produced from technical-grade oxide in two very different ways. Molybdenum trioxide can be purified by a sublimation process because molybdenum trioxide has an appreciable vapor pressure above 650°C, a temperature at which most impurities have very low volatiUty. The alternative process uses wet chemical methods in which the molybdenum oxide is dissolved in ammonium hydroxide, leaving the gangue impurities behind. An ammonium molybdate is crystallized from the resulting solution. The ammonium molybdate can be used either directly or thermally decomposed to produce the pure oxide, MoO. ... 

Manufacturing Processes. Ammonium molybdate or molybdenum trioxide is reduced to molybdenum metal powder by hydrogen in a two-stage process. In the first stage, MoO or ammonium molybdate is reduced to molybdenum dioxide, M0O2, at temperatures around 600°C in the... 

Molybdenum dioxide (Mo0a) is prepared4 6 by ignition of the trioxide MoOs in a stream of dry hydrogen at 450°C for three hours. A combustion tube and circular oven (see No. 14) are used. It is not necessary to remove the remain-... 

By increasing the value given to n, the Mo03 structure is ultimately obtained in all these series. It is evident that, at least in theory, topochemical reduction of MoOs should be made possible by such a shear mechanism initially appearing along very widely separated dislocation lines this may be the clue to the structure of the discolored molybdenum trioxide crystals which are the main product when Mo03 is heated strongly in vacuo (12). 

The presence of moisture induces oxidation even at room temperature in long storage . The ultimate product of this oxidation is almost certainly molybdenum trioxide, but it has been suggested that the primary product at elevated temperatures in the absence of air is an oxysulphide MoOS, with the release of gaseous hydrogen. 

The oxychloride MoO Clg is obtained when chlorides of molybdenum are heated in the air, and, among other compounds, when the dioxide, or a mixture of the trioxide with carbon, is heated in chlorine, or when molybdenum trioxide and phosphorus trichloride are heated together it is not formed, however, when a mixture of common salt, sulphuric acid, and molybdenum trioxide is heated cf. p. 28). A pale yellow amorphous substance, soluble in water and alcohol, it is easily sublimed, and is reduced on heating in hydrogen or carbon monoxide to the dioxide. 

---