摘要：(1) The reaction of Gries Romijin reagent with NO2- ion was accelerated by adjusting the pH of reaction mixture at 4.0. At this pH, the color developed was stable. The estimation of micro-amounts (0.01∼0.4 ppm) of NO2- ion was performed with a good sensitivity. (2) NO3- was quantitatively reduced to NO2- with Mn2+ in ammonia alkali solution and reacted with G.R. reagent at pH 4.0. The estimation of 0.02∼0.6 ppm of NO3- was thus performed. Since coexisting NO2- is stable in the reduction conditions, NO3- and NO2- in one mixture can be estimated separately.
