Separation and identification of Group I cations in the presence

5 Separation and identification of Group I cations in the presence of thallium and tungsten 

Molybdenum is a silverish-white, hard, heavy metal. In powder form it is grey. It melts at 2622°C. The metal is resistant to alkalis and hydrochloric acid. Dilute nitric acid dissolves it slowly, concentrated nitric acid renders it passive. Molybdenum can readily be dissolved in aqua regia or in a mixture of concentrated nitric acid and hydrogen fluoride. 

Molybdenum forms compounds with oxidation numbers -1-2, 4-3, 4-4, 

and 4-6. Of these, molybdates are the most important (with oxidation number 4-6). Molybdates are the salts of molybdic acid, H2M0O4. This acid tends to polymerize with the splitting off of molecules of water. Thus, the commercial ammonium molybdate is in fact a heptamolybdate in which [Mo7024] ions are present. For the sake of simplicity the formula MoO will be used in this text whenever molybdates are discussed. 

2-3 times with 1 ml portions of cold water, and reject the washings. Transfer the precipitate to a boiling tube or to a small beaker, and boil with 10-15 ml water. Filter hot. 

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