FIELD: analytical chemistry. SUBSTANCE: aqueous solution of ammonium molybdate (final concentration is 2·10-4 M), solution of ammonium vanadate in 0.03M HCl (2·10-3 М) and sulfuric acid solution (final concentration is 0.01 N) are added to examined sample. Triple heteropolyacid formed is reduced by adding of ascorbic acid up to concentration 0.5%. Prepared solution is heated on the boiled bath for 10 min, cooled and safranine-T solution is added up to concentration 1·10-3 %. Reduced heteropolyacid forms associate with dye. A mixture of methylethylketone and butylacetate at the ratio 3:2 is added to analyzed solution, and the volume of aqueous solution must 2-fold exceeds that of volume of organic mixture. After extraction organic fraction is subjected for photometry at 530 nm. Phosphorus content is calculated by calibrating plot. EFFECT: improved method of assay. 2 tbl
