测定氨根或者凯氏氮

The potentiometric titration of Kjeldahl nitrogen is one of the most widely employed analytical methods. Many of the standard procedures used in the food and animal feed industry, in waste water and refuse analysis as well as in agriculture and the fertilizer industry are based on this method. Extensive test series (interlaboratory tests) have been carried out to determine and optimize the recovery rates and digestion conditions. The knowledge derived from these tests has been integrated in the corresponding standards. Normally, the samples are digested with concentrated sulfuric acid using a catalyst as admixture. The ammonium sulfate formed is distilled off as ammonia in alkaline solution, collected in an absorption solution and then titrated. The first part of this bulletin describes in detail the potentiometric determination of nitrogen after distillation of the digestion solution. The second part indicates the possibilities of the coulometric titration (without distillation).