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用电势法研究肼N_2H_4还原Ag(NH_3)_2~+溶液以沉析银的反应条件,获知体系中氨的含量、pH值、温度以及杂质(如Cu、Fe等)的存在,对该反应的速度都有较大的影响.在摩尔比为Cl~-:NH_3:Ag~+=3.3:15:1的体系中,获得最合适的反应条件:溶液的初始酸度pH=12.2,温度为50℃. 在上述最合适的反应条件下,将肼N_2H_4不断地加入Ag(NH_3)_2~+溶液中,当体系电势下降至-250mV(vs SCE)时,停止加入N_2H_4,迅速中止反应,此时银的还原沉析率为99.5％,银的纯度由88.3％(系Ag在体系金属中所占的含量)提高到99.8％.
Potential method was used to study the reaction conditions of reducing Ag (NH_3) _2 ~ + by hydrazine N_2H_4 to precipitate silver. The content of ammonia, pH, temperature and impurities (such as Cu and Fe) in the system were determined. In the system with molar ratio of Cl ~ -: NH 3: Ag ~ + = 3.3: 15: 1, the most suitable reaction conditions were obtained: the initial acidity of the solution was pH = 12.2 and the temperature was 50 ℃ Hydrazine N 2 H 4 was continuously added to Ag (NH 3) 2 + solution under the above optimum reaction conditions. When the potential of the system decreased to -250 mV (vs SCE), the addition of N 2 H 4 was stopped and the reaction was stopped rapidly. At this time, silver The reduction and precipitation rate was 99.5%, the purity of silver increased from 88.3% (the content of Ag in the system metal) to 99.8%.