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土壤镁的测定,常用EDTA络合滴定,该法对钙、镁含量低的土壤,要求较大的称样量,这给氢氟酸-过氯酸熔样带来一定困难,而且需两次滴定,较繁琐。近年,一些土壤实验室用原子吸收分光光度法测镁效果较好,但需特殊设备。达照黄比色法测镁历史较久,近年虽不断出现一些新的比色法,如二甲酚橙,二甲苯胺兰Ⅱ,铬黑T等,但达旦黄法快速、简单、灵敏度高,仍不失为一种好方法。本文用氢氟酸-过氯酸熔样,六次甲基四胺沉淀铁、铝等干扰元素,三乙醇胺掩蔽尚未除尽的少量铁、铝,盐酸羟胺还原可溶性锰,无需破坏铵盐和加钙离子。方法简单,具有一定的准确度和精密性,现将实验情况介绍于下。
Soil magnesium determination, commonly used EDTA complexometric titration, the method of calcium, magnesium content of the soil, requires a larger scale, which gives the hydrofluoric acid - perchloric acid melt sample brings some difficulties, but also twice Titration, more complicated. In recent years, some soil laboratories use atomic absorption spectrophotometry to measure magnesium better, but need special equipment. Up to yellow colorimetric magnesium test history for a long time in recent years, although there have been some new colorimetry, such as xylenol orange, xylidine amine blue Ⅱ, chrome black T, etc., but the Dan yellow method fast, simple, high sensitivity , Is still a good way. In this paper, hydrofluoric acid - perchloric acid melt sample, hexamethylenetetramine precipitation of iron, aluminum and other interfering elements, triethanolamine masking not yet done a small amount of iron, aluminum, hydroxylamine hydrochloride to reduce soluble manganese, without destroying the ammonium salt and added Calcium ions. The method is simple, with a certain degree of accuracy and precision, the experimental conditions are introduced below.