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Phosphomolybdate Potassium Antimonyl Tartrate
Q. First, I apologize for my inconvenience. And my English is not good; please excuse that. I am doing a seminar about: "determine Phosphate in Seawater by Ascorbic acid Method". I had consulted many documents but I still don't understand about mechanism of formation of phosphomolydate such as conditions (is acidic not base), effect of some metals: Cr(6), Nitrit, and the role of Potassium Antimonyl Tartrate in formation complex.
Pham Thai PhuongStudent - HaNoi, VietNam
2004
A. The theory is that phosphates in the sea are converted to orthophosphates by the action of UV light on them. This orthophosphate reacts with the acidified molybdate reagent and potassium antiminoyl tartrate to form a heteropoly acid (phosphomolybdic acid). This is reduced to the intensely coloured molybdenum blue compound by its reaction with ascorbic acid, which is a mild reducing agent. The resulting blue colour is measured at 880nm in a spectrophotometer and after calibration, the amount of phosphorous originally present can be calculated. Oxidising agents such as Cr(VI)will obviously compete with the phosphomolybdic acid in the reaction with ascorbic acid, so excess ascorbic acid would be required. Reducing agents, conversely, will compete with the ascorbic acid in reducing the phosphomolybdic acid and therefore interfere with the amount of molybdenum blue produced.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2004
Holy Crap...Trevor.. you are Da'Man!
Marc Green
anodizer - Boise, Idaho
2004
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