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本文利用偶氮胂M与钙形成天蓝色的络合物作为终点指示,在pH≥12.5碱性溶液中,以EDTA络合滴定,终点变化敏锐。在80毫升滴定溶液中,氧化钙量在0—20毫克范围与EDTA消耗量呈良好线性关系;大于20毫克时,终点变化迟钝,结果易偏高。当以三乙醇胺为掩蔽剂,对20毫克氧化钙,共存离子允许量(毫克)为:Fe~(3+)、Al~(3+)(20);Mg~(2+)、Pb~(2+)、Ni~(2+)、V(Ⅴ)、Mo(Ⅵ)、F~-(10);Cu~(2+)(7.5);Zn~(2+)、W(Ⅵ)、Ti(Ⅳ)、Zr(Ⅳ)、Cr(Ⅵ)、PO_4~(3-)(5);Au~(3+)(2.5);Mn~(2-)(2);Ag~+、La~(3+)、Ce~(3+)(1)。方法适用于水和碳酸盐岩石中钙的测定。
In this paper, arsenazo M and calcium to form azure complex as an end point in the pH ≥ 12.5 alkaline solution, EDTA complexation titration, end point sensitive. In 80 ml titration solution, the amount of calcium oxide in the range of 0-20 mg and EDTA consumption showed a good linear relationship; greater than 20 mg, the end point of change slow, the results tend to be high. When triethanolamine is used as masking agent, the allowable amount of coexisting ions (mg) for 20 mg of calcium oxide is: Fe 3+, Al 3+ 20; Mg 2 +, Pb ~ (2 +), Ni ~ (2 +), V (Ⅴ), Mo (Ⅵ) and F ~ - (10) (Ⅲ), Cr (Ⅵ), PO_4 ~ (3 -) (5); Au ~ (3 +) (2.5); Mn ~ (2 -) ~ (3 +), Ce ~ (3 +) (1). The method is suitable for the determination of calcium in water and carbonate rocks.