溶液中钙镁含量准确测定的方法研究

Method for Accurate Determination of Solution Containing Calcium and Magnesium

经典测定钙、镁含量的方法是用EDTA标准溶液滴定钙镁总量后再滴定钙,此方法对于含钙、镁离子盐水体系溶解度的测定,尤其在镁含量较高的情况下,其分析精度和准确度远远达不到要求。针对硝酸钙、硝酸镁混合样品,采用EDTA质量滴定法测定钙镁总量,用草酸钙沉淀法从镁中定量分离钙,然后运用差减法计算出镁的含量。实验结果表明,当混合溶液中镁钙的质量比不超过10∶1时,钙、镁离子分析结果的相对误差在±0.3%之内,但镁钙的质量比超过10∶1时,相对误差达到1%。因此,在一定的镁钙质量比范围内,此方法可用于盐水体系中钙、镁含量的准确测定。

Traditionally, the method of the EDTA titration, which is used to titrate total content of calcium and magnesium and the content calcium,is difficult to determine the content of Ca^2 ＋ and Mg^2 ＋in sah-wa- ter solution which the amount of magnesium present the high precision requirement of solubility data. In is more .than the calcium. The accuracy can＇ t reach this paper, the total content of calcium and magnesi-um was determined with EDTA mass titration for mixture solution containing calcium nitrate and magnesi- um nitrate. Calcium can be quantitatively separated from magnesium using calcium oxalate gravimetric method. Then the content of magnesium can be obtained by subtraction. The results show that when the mass ratio of Mg^2＋ ： Ca^2＋ is less than 10：1 ,the relative errors of analysis results can be controlled within ＋0. 3%. While the mass ratio is more than 10：1 ,the relative error approaches 1%. So this method can be applied to determine the contents of calcium and magnesium within a certain range of the mass ratio of magnesium and calcium in salt-water system accurately.