Fig. 1. Absorption spectrum of thiourea reduced phosphomolybdate complex
formed from the solution containing 1 ml of 50g/ml phosphate + 0.5 ml of
5.54×10−4 M ammonium molybdate + 0.5 ml of 0.25N sulfuric acid+1ml of 2%
thiourea diluted to 10 ml with water.