摘要：A sample of well water in Yokohama city was found to contain both the residual chlorine and nitrite nitrogen. Ammonia nitrogen (7.5 ppm) too was found in this water. According to the conventional concepts, it seemed impossible that the residual chlorine and nitrite nitrogen could exist in the water at the same time. We found the nitrite nitrogen could be produced under certain conditions from ammonia nitrogen in the presence of residual chlorine. Thus, when water, the pH of which was above 8.0 and which contained several ppm of ammonia nitrogen, was disinfected with chlorine, the production of nitrite nitrogen was detected. However, when the pH was lower than 7.0 or the amount of ammonia nitrogen was less than 1 ppm, the nitrite nitrogen could not be detected.
