• Ammonia can be determined spectrophotometrically by reaction with phenol in the presence of hypochlorite. A 2.39 mg of sample of protein of unknown concentration was chemically digested to convert its nitrogen into ammonia and then diluted to 100 mL. 10 mL of the solution were placed in a 50mL volumetric flask. After adding 5 mL of phenol solution and 2 mL of sodium hypochlorite solution, the solution becomes blue in color, and was diluted to 50 mL. The absorbance was then measured at 625 nm in a 1 cm cuvette after standing for 30 min. In another measurement, a standard solution was prepared from 0.01 g of NH4Cl (53.49 g/mol) dissolved in 1 L of water. Then 10 mL of this standard were placed in a 50-mL volumetric flask and analyzed in the same manner as the unknown. A reagent blank was prepared by using distilled water in place of unknown