The determination of nitrogen trichloride in liquid chlorine

Methods are described for the determination of nitrogen trichloride over the range of concentrations at which it exists in chlorine manufacture and handling. The methods are based on the conversion of nitrogen trichloride to ammonium chloride by hydrochloric acid and the determination of ammonium by spectrophotometry as the indophenol complex or by potentiometry with an ammonia gas-sensing electrode; higher levels of nitrogen trichloride are determined by titration. For liquid chlorine, a sample is taken in a refrigerated trap containing hydrochloric acid. After that, the chlorine is slowly evaporated at atmospheric pressure. Results of tests are given to prove the reliability of the methods.