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土壤全量氮的测定,沿用较久的为H_2SO_4——混合盐消化的凯氏法,但由于消煮时间长,在大跃进中改用硫酸——重络酸钾法消化,加快了消煮速度,但不能摆脱蒸溜的繁杂手续,同时NaOH耗量大,用电亦多,因此为了克服这一些缺点,采用比色法。 一、方法原理 土壤用硫酸消化过程中所发生的化学反应是极其复杂的,浓硫酸具有从很多有机化合物取去水分的能力,这样有机质变为黑色(被碳化),蛋白质在酸的作用下遭受到水解,分解成氨基酸。硫酸受热分解出SO_2,将氮还原成氨,而氨却被过剩硫酸吸收,然后吸取部分溶液加奈勒试剂进行比色。
Determination of soil total nitrogen, followed by H_2SO_4 - mixed salt digestion Kjeldahl method, but due to a long digestion and digestion, in the Great Leap Forward use sulfuric acid - potassium rec acid potassium digestion, speed up the digestion speed , But can not get rid of the complicated procedures of steaming, NaOH consumption at the same time, power is also more, so in order to overcome these shortcomings, the use of colorimetry. I. PRINCIPLE OF THE METHOD The chemical reaction that takes place in the digestion of soil with sulfuric acid is extremely complex. Concentrated sulfuric acid has the ability to remove water from many organic compounds so that the organic matter turns black (carbonized) and the protein suffers under the influence of acids To hydrolysis, decomposition into amino acids. Sulfuric acid decomposes SO2 by heating, reduces nitrogen to ammonia, and ammonia is absorbed by excess sulfuric acid, and then a part of the solution is added to the reagent to perform colorimetric analysis.