1. General Discussion
a. Principle: In the presence of sulfuric acid, potassium sulfate, and mercuric sulfate catalyst, the amino nitrogen of many organic materials is converted to ammonium bisulfate. After the mercury ammonium complex in the digest ate has been decomposed by sodium thiosulfate, the ammonia is distilled from an alkaline medium and absorbed in boric acid. The ammonia is determined colorimetrically, or, if preferred, by titration with a standard mineral acid.