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钙和镁的测定一般采用络合滴定法,但终点不甚清晰,而且钙镁比例只允许为1:10-10:1,有的方法虽然提高比例到30倍,但不简便,干扰因素颇多。高鸿等对大量镁存在下钙的交流示波极谱滴定,解决了络合滴定中钙的测定问题。本文在此基础上讨论钙镁的连续滴定。在pH=10的含有0.1M氨液中,EGTA与Ca~(2+)、Zn~(2+)、Mg~(2+)络合的表观稳定常数分别为:logK’_(Ca-EGTA)=10.9;logK’_(Zn-EGTA)=8.2;logK’_(Mg-EGTA)=5.2。在含有1.0M氨液中,EGTA与Zn~(2+)的表观稳定常数为:logK’_(Zn-EGTA)=3.6,DCTA与Ca~(2+),Mg~(2+),Zn~(2+)络合的
The determination of calcium and magnesium in general by complexometric titration, but the end is not clear, and the ratio of calcium and magnesium only allows 1: 10-10: 1, although some methods to improve the ratio to 30 times, but not easy, quite disturbing factors many. Gao Hong and other large amount of magnesium in the presence of calcium exchange oscillopolarographic titration, to solve the determination of calcium complexation titration problems. This article discusses the continuous titration of calcium and magnesium on this basis. The apparent stability constants of EGTA complexed with Ca2 +, Zn2 + and Mg2 + in 0.1M ammonia solution with pH = 10 are logK ’_ (Ca- EGTA) = 10.9; logK ’_ (Zn-EGTA) = 8.2; logK’ _ (Mg-EGTA) = 5.2. The apparent stability constants of EGTA and Zn 2+ in 1.0M ammonia solution were logK ’_ (Zn-EGTA) = 3.6, DCTA and Ca 2+, Mg 2+, Zn ~ (2+) complexed