紫脲酸铵分光光度法测定复盐法水氯镁石脱水产品中氧化镁

对于水氯镁石的复盐(C6H5NH2·HCl·MgCl2·6H2O)法脱水产品中微量MgO含量的测定,采用了直接测定样品水溶残渣中镁含量而得MgO含量的方法代替传统的间接法,获得了更准确的结果。用紫脲酸铵分光光度法测定了水溶残渣用稀H2SO4溶解后溶液中微量镁,研究了金属镁离子与显色剂的络合比、溶液酸度、显色时间对显色的影响,以及盐酸苯胺阳离子、Fe3+、Zn2+、Ba2+、Ca2+、Ni2+、Co2+等离子对显色的干扰及其消除。并采用修正法消除了显色后残余显色剂对测定镁的影响。结果表明,在镁离子浓度0~2mmol/L范围内,修正吸光度与镁离子浓度呈线性关系,摩尔吸光系数为2.45×102 L/(mol·cm)。加标镁离子的测定结果证明该法具有较高的精密度和准确度（加标回收率近100%）,适合于水氯镁石脱水产品中总MgO含量的准确测定。

Murexide Spectrophotometric Determination of Magnesium Oxide in Dehydration Products of Bischofite from Hydrated Double Salt Method

For determination of MgO in dehydration products of hydrated double salt (C6H5NH2·HCl·MgCl2·6H2O), that direct measurement of the MgO in the water-insolvable residue of dehydration product samples was substituted for the conventional indirect method yielded more accurate results. The water-insolvable residue was resolved by boiling diluted H2SO4 solution and the microgram amount magnesium in the solution was measured by spectrophotometry, using murexide as a color reagent. The effects such as pH of solution, complex ratios of magnesium to murexide, dosages of chromogenic reagent, reaction time on the absorbances of coloured solutions, and the tolerance limits of some interfering ions such as C6H5NH2·H+、Fe3+、Zn2+、Ba2+、Ca2+、Ni2+、Co2+ and their masking reagents are investigated. The calibration curve is established under completely deduction of the absorbance of remnant colour reagent according to the correction spectrophotometric theory. In the concentration range of 0~2 mmol/L of Mg2+, the calibration curve is linear and molar absorptivity 2.45×102 L/(mol·cm). The experimental results show that this method can give high precisions and accuracies (recoveries of standard addition were close to 100%), therefore it is suitable for analysis of the MgO in dehydration products.