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本文对铜锌合金中铜、锌的无氰络合滴定进行了探讨。试液中的Cu(Ⅱ)、Zn(Ⅱ)先在pH5～6条件下以PAN为指示剂,用EDTA标准溶液进行络合,继而在强碱性介质中用过量肼在约70℃条件下将Cu-EDTA中的Cu(Ⅱ)定量还原成金属铜,此时Zn-EDTA络合物也有部分解离,游离出的Zn(Ⅱ)在强碱性中呈Zn(OH)_4~(2-)或ZnO_2~(2-),然后加盐酸使溶液呈强酸性,使ZnO_2~(2-)转变为Zn(Ⅱ),再调至pH5～6,以二甲酚橙为指示剂,用锌标准溶液反滴溶液中释出的EDTA。实验步骤称取0.1克试样置于250毫升锥形瓶中,加入浓盐酸5毫升,过氧化氢1毫升,加热溶解,煮沸使多余的过氧化氢分解。加酒石酸溶液(20%)5毫升,用
In this paper, copper and zinc in copper-zinc alloy non-cyanide complexation titration were discussed. The Cu (Ⅱ) and Zn (Ⅱ) in the test solution are firstly complexed with EDTA standard solution under the condition of pH 5-6 with PAN as an indicator, and then treated with excess hydrazine in strong alkaline medium at about 70 ° C. The Cu (Ⅱ) in Cu-EDTA was quantitatively reduced to Cu, and the Zn-EDTA complex also partially dissociated. The Zn (Ⅱ) -) or ZnO_2 ~ (2-), then add hydrochloric acid to make the solution strong acid, make ZnO_2 ~ (2-) convert to Zn (Ⅱ), then adjust to pH5 ~ 6, using xylenol orange as indicator, EDTA released from the titration solution of zinc standard solution. Experimental procedure Weigh 0.1 g sample placed in 250 ml Erlenmeyer flask, add 5 ml of concentrated hydrochloric acid, hydrogen peroxide 1 ml, heated to dissolve, boil the excess hydrogen peroxide decomposition. Add tartaric acid solution (20%) 5 ml, with