Photometric determination of nitrogen. Wet incineration followed by formation of indophenol blue with salicylate/hypochlorite.

Ammonia in wet incineration residues has been analyzed photometrically by a modified Berthelot reaction using a water-free digestion mixture. Phenol is substituted by salicylate in the dye-producing reaction. The method can be adapted for any biological material with a minimum content of 0.04 mug N/sample. Nonprotein nitrogen may be determined in the supernatant of TCA precipitates.