Treatment of ammonia with phenol in the presence of hypochloriteyields indophenol, a blue product absorbing light at 625 nm, whichcan be used for the spectrophotometric determination ofammonia.
To determine the ammonia concentration in a sample of lakewater, you mix 10.0 mL of lake water with 5 mL of phenol solutionand 2 mL of sodium hypochlorite solution and dilute to 25.0 mL in avolumetric flask (sample A). To a second 10.0 mL solution of lakewater you add 5 mL of phenol, 2 mL of sodium hypochlorite, and 2.50mL of a 5.50
