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铬黑T(EBT)是镁较为灵敏的显色剂,但由于钙的严重干扰,影响它在分析中的应用。根据配位体缓冲原理,考虑到EGTA和EBT与钙、钡、镁间络合物稳定常数的差别,本试验以EGTA和EGTA—Ba联合掩蔽钙,EBT显色镁,取得良好效果。显色液中多至5.6毫克氧化钙不影响镁的测定,钙量少时可单用EGTA掩蔽。方法可用于石灰石及其它矿石和含钙合金中少量镁的测定。
Chromium Black T (EBT) is a more sensitive reagent for magnesium, but its serious interference with calcium affects its application in analysis. According to the principle of ligand buffering, considering the difference of the stability constants of EGTA, EBT and calcium, barium and magnesium complexes, EGTA and EGTA-Ba were used to mask the calcium and EBT chromogenic magnesium to obtain good results. Up to 5.6 mg of calcium oxide in the color developing solution does not affect the determination of magnesium, but can be masked with EGTA only when the amount of calcium is small. The method can be used for the determination of a small amount of magnesium in limestone and other ores and calcium-containing alloys.