Molybdate Reference Compounds

Similarly, comparison of the Mo K edge absorption spectra for tailings and reference compounds of known oxidation states (Fig. 2), shows that Mo6+ is the dominant form of molybdenum in the mine tailings. The characteristic pre-edge feature in the near edge spectra indicates that Mo in the tailings occurs mostly as a molybdate. 

The Barin tables are far more complete in coverage than any of the sources described above. All of the natural elements and their compounds are included. In addition to the substance types listed in USBM Bull 677, the Barin tables include a large number of ternary oxides - aluminates, arsenates, borates, chromates, molybdates, nitrates, oxy-halides, phosphates, titanates, tungstates, selenates, vanadates, zirconates, etc. - as well as cyanides, hydroxides, complex silicates and inter-metallic compounds. The only substances not included by Barin, for which tables can be found elsewhere, are the ionized-gas species and a limited number of gas species important only at very high temperatures, which are listed in the JANAF tables. For each table Dr. Barin gives references for each of the major thermochemical values employed (enthalpy of formation and entropy at 298 K, and heat capacity). Like the USBM Bulletins, no attempt is made to discuss the choice between conflicting data sources. 

A catalyst containing bismuth and molybdenum oxides was used many years ago by Tanner (130) for the oxidation of acetylene, but only recently have similar catalysts been employed for the oxidation of mono-olefins. Often bismuth phosphomolybdates are referred to, although the phosphorus does not appear to be necessary. For simplicity we refer to catalysts with characteristic properties of the bismuth-molybdenum oxide group as bismuth molybdate, and this phrase is not intended to imply a definite crystalline compound. 

Salter (1869) also discusses what he refers to as persulpho-molybdates , compounds of various metals with persulpho-molybdic acid barium gives a red colour, calcium a scarlet, chromium, uranium, lead, platinum and copper a dark red. Other reds were obtainable from zinc, cadmium, iron, mercury and tin. 

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