Molybdates

Molybdates are compounds containing molybdenum oxyanions in which molybdenum has the formal oxidation number of +6, but in general usage the term is often extended to cover any compound containing molybdenum and oxygen. Confusingly, the word “molybdate” is also part of the name of a number of compounds which contain molybdenum as part of non-oxygen-containing polyatomic ions, such as ammonium tetrathiomolybdate, in which molybdenum is bonded to four sulfur atoms. Molybdates are most often used as catalysts in petroleum refining, polymer production, and other industrial chemical processes. Additionally, sodium molybdate can be used as a corrosion inhibitor in industrial water treatment, and molybdate salts are added to some types of fertilizers, due to the requirement of molybdenum for the function of nitrogen fixation enzymes in legumes. Some molybdates are brightly colored, and have been used as specialty pigments and in colorimetric chemical tests.