ABSTRACT

Atmospheric nitrogen is an inert gas which relatively few organisms can convert to usable forms such as ammonia, nitrate, and nitrite. Nitrate concentration, if higher than 45 mg/l in drinking water, causes an illness in infants called methemoglobinemia. In the brucine method, nitrate reacts with brucine sulfate in a glacial acetic and dilute sulfuric acid mixture. Several different metals and alloys have also been used to determine nitrate and nitrite, but ferric and fluoride ions interfere with the analysis. The total or Kjeldahl nitrogen standard method determines free ammonia and organically-bound nitrogen in the −3 valence state but does not determine nitrites, azides, nitro, nitroso, oximes, or nitrates. Ammonium ion in normally alkaline waters is in equilibrium with free ammonia, which is toxic to fish and other aquatic forms. The direct phenate method, which uses the reaction of ammonia, hypochlorite, and phenol catalyzed by manganous ion to produce an intense blue color, is subject to interferences from acidity and alkalinity.