However, the color developed solutions contain the heavy metals, vanadium and molybdenum. Be sure to put them in the aqueous waste container, as directed by your instructor. There are two parts to this analysis. Then the resulting solution must be diluted and treated with a reagent, ammonium vanadomolybdate, which forms a yellow compound with phosphate. The intensity of the color depends on the concentration of the phosphate and the solutions are analyzed with a spectrophotometer by comparison to a calibration curve.
More detailed instructions follow.
Put excess H 2 SO 4 in the aqueous waste container. Cover the flask with an inverted beaker or watch glass. Suspend the flask in a larger beaker of water, which contains a few boiling chips, on a hot plate in the hood. Boil the water for 30 minutes, replenishing evaporated water as needed. Allow to cool and transfer the contents to a 250 ml volumetric flask.