Molybdic metaphosphate

The P+s anions are prepared from molybdic acid and a metaphosphate or pyrophosphate. Manganese, cobalt, and copper form solutions of the divalent cations with paramolybdate anion. 

Pyro- and metaphosphates give the ammonium molybdate test on warming for some time this is doubtless due to their initial conversion in solution into orthophosphates. The chief differences between ortho-, pyro- and metaphosphates are incorporated in the following table. The student should carry out all the tests. To study these reactions use freshly prepared solutions of sodium pyrophosphate and sodium metaphosphate. 

In subsequent schemes of qualitative analysis, orthophosphates, obtained in Group III separations, were distinguished from pyro and the so-called metaphosphates by the ammonium molybdate test. 

If a solution of ammonium molybdate in concentrated nitric acid is added in excess to an orthophosphate solution, a yellow precipitate of ammonium phosphomolybdate is obtained in the cold or with very slight warming (1). No reaction is obtained from pyro or metaphosphates under the same conditions, but, if they are heated, hydrolysis will occur and orthophosphates will be detected. 

Metavanadates, metaphosphates Ortho- and pyro-vanadates, molybdates, tungstates, chromates, phosphates, etc. 

Ammonium hydroxylamine - 658 Ammonium iodide - 611 Ammonium lactate - 611 Ammonium lauryl sulfate -183 Ammonium metaphosphate - 27,54,114, 123, 154, 156, 252, 263, 273, 658,810, 823 Ammonium metatungstate - 183 Ammonium molybdate - 231, 609, 611 Ammonium muriate (see Ammonium chloride) Ammonium nitrate -12.19,27, 33, 37.47,54,... 

General uniform corrosion on pure magnesium has been drastically reduced by the use of inhibitors sueh as ehromate, dichromate, molybdate, nitrate, phosphates and vanadates that promote the formation of a protective layer, tend to retard corrosion (Ghali, 2006). Addition of substances that can form soluble complexes as tartrate, metaphosphate, etc. or insoluble salts as oxalate, carbonate, phosphate, fluoride, etc. is efficient at reducing corrosion. Adding soluble chromates, neutral fluorides or rare earth metal salts is effective in reducing magnesium-base metal corrosion (Schmutz et al, 2003). 

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