Photometric determination of phosphorus in ferroalloys by the extraction of phosphovanadomolybdic acid

Abstract

A rapid method for the determination of phosphorus in ferroalloys which involves the extraction of phosphovanadomolybdic acid with methyl isobutyl ketone from acidic aqueous solution has been presented.
Optimum conditions for the formation of phosphovanadomolybdic acid were: (1) acid; sulfuric acid (0.81.5N), perchloric acid (0.81.6 N) and nitric acid (0.92.7 N), (2) amounts of reagents; 25ml of 1.2% ammonium vanadate solution and 5 ml of 10% ammonium molybdate solution, and (3) total volume of aqueous solution; 50 ml. The sample solution preliminarily adjusted to fulfill above conditions was shaken with 10 ml of methyl isobutyl ketone for 1020 sec. After standing, the organic layer was dry-filtered and its absorbance was measured. In addition, extraction ratio, mutual dissolution of acid solution and methyl isobutyl ketone, stability of extracts and the effect of heating on the result were examined.
The method has higher sensitivity at shorter wavelengths, and 1400μg of phosphorus could be determined with the same method by selection of wavelengths from 340 mμ to 460 mμ. Interfering elements and compounds were Ti, As, W, Cr, Si, Nb, Sn, Sb, large amounts of sulfate, organic acids and salts, and reducing agents.
The phosphorus in ferromanganese, ferrosilicon, silicomanganese and ferromolybdenum were determined. The accuracy was 0.83.2%.