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利用Cd、Zn在示波极谱图上具有敏锐的切口及Cd、Zn与EGTA和与NH_3所生络合物稳定常数的差异,用交流示波极谱滴定法,在pH=10的NH_4OH-NH_4Cl缓冲溶液中,先用EGTA直接滴定Cd,用Cd切口的消失指示终点,再用EDTA直接滴定Zn,终点直观,方法简单、快速、准确、经济。连续滴定,测Zn时,Cd/Zn比达85,测Cd,Zn/Cd比达20,直接滴定大量Zn中Cd,Zn/Cd比可高达1000,比文献上已有的方法优越。
Using Cd and Zn, there are sharp incisions on the oscillopolarographic polarography and the differences of the stability constants of Cd, Zn, EGTA and NH 3 complexes. Using the AC oscillopolarographic titration method, the pH value of NH_4OH- NH_4Cl buffer solution, the first direct titration of Cd with EGTA, the disappearance of Cd incision indicates the end point, and then direct titration of EDTA Zn, the end point intuitive, the method is simple, fast, accurate and economical. Continuous titration and determination of Zn, Cd / Zn ratio of 85, measured Cd, Zn / Cd ratio of 20, direct titration of a large number of Zn in the Cd, Zn / Cd ratio up to 1000, than the literature has been superior.