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于pH5.5—6的乙酸-乙酸钠缓冲溶液中,先以EDTA络合滴定铅锌合量,再将此溶液调至pH6—6.5,以邻二氮菲(Phen)从Zn-EDTA络合物中夺取锌使成Zn-Pben,定量释放出EDTA,继以硝酸铅滴定,从而测得锌量。经试验表明,1.2克Phen可从Zn-EDTA中夺取1毫克锌。铜、铁有干扰,若加入10毫升8%硫脲溶液,则允许共存20毫克铜。加入Phen后再补加约1克固体硫脲,可使锌的滴定终点更敏锐;加入15毫升4%氟化钠溶液,且缓冲液中乙酸钠浓度达40%时,即使共存40毫克铁也不影响铅的测定。方法应用于铅锌矿中铅锌的测定,结果满意。
In pH5.5-6 acetic acid - sodium acetate buffer solution, first titration with EDTA complex titration of lead and zinc, and then the solution was adjusted to pH6-6.5, with phenazine from Zn-EDTA complex The zinc in the material was taken as Zn-Pben, and the EDTA was released quantitatively, followed by titration with lead nitrate to measure the amount of zinc. It has been experimentally shown that 1.2 grams of Phen can take 1 milligram of zinc from Zn-EDTA. Copper, iron interference, if added 10 ml 8% thiourea solution, then allow the coexistence of 20 mg copper. After the addition of Phen and then add about 1 g of solid thiourea, zinc titration endpoints can be more acute; adding 15 ml of 4% sodium fluoride solution, and the buffer sodium acetate concentration of 40%, even with the coexistence of 40 mg of iron Does not affect the determination of lead. The method was applied to the determination of lead and zinc in lead-zinc mine with satisfactory results.