This is a rapid method, applicable to relatively pure waters. For colored or impure waters, in particular those containing more than 5 mg of iron per liter or those whose hardness exceeds 20 m/1, prior dis illation (see NBN T 91-252) is necessary. The method is applicable to waters containing up to 2 mg of ammoniacal nitrogen per liter without dilution. Certain aliphatic and aromatic organic compounds (amines, chloramines, hydrazine, ketones, aldehydes, etc.) can make the method precarious.
NBN T 91-251-1976 history
1975NBN T 91-251-1976 Water analysis methods — Determination of the ammoniacal nitrogen — Direct photometric method with Nessler reagent