Abstract：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.
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2015, Vol. 36 
