Spectrophotometric determination of nitrite and nitrate in doped potassium chloride crystals

Research paper by W. Gomes

Indexed on: 01 Dec '66Published on: 01 Dec '66Published in: Analytical and Bioanalytical Chemistry


KCl crystals, doped in the melt with KNO2 or KNO3, contain both NO2− and NO3− ions. Spectrophotometric methods are described for the determination of the admixture concentration after dissolving the crystals. Nitrite is determined by colorimetry of an azo dye formed in methanol-water-HCl medium from p-nitroaniline and α-naphthylamine. The absorption is proportional to the nitrite concentration in the range of 5 · 10−6 to 5 · 10−5 M NO2− UV absorption measurement is employed for the spectrophotometric determination of nitrate, Beer's law being obeyed between 3 · 10−5 and 3 · 10−4 M NO3− at 220 nm. Here, nitrite is removed by adding sulfamic acid, and correction is made for chloride. Some results on nitrite- and nitrate-doped crystals are given.