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对于常量碲的分析,应用最广泛的是重铬酸钾容量法。但由于Cr~(6+)/Cr~(3+)(1.33V)与Te~(6+)/Te~(4+)(1.02V)标准电位差比较小,致使Cr~(6+)与Te~(4+)的氧化还原反应速度比较慢。美国ASTM(Annual Book of ASTMStandards,part 12,P423,1976)规定用重铬酸钾法测定铜合金中的碲,要放置15分钟以后,再用Fe~(2+)进行电位滴定。另外,该方法中采用硝酸(1+1)直接溶样,对于含锡的铜合金将由于锡酸沉淀的析出吸附碲,导致结果偏低。为此,本文就影响重铬酸钾与碲反应速度的有关因素及合理的溶解酸的选择,进行了实验探讨。分析方法称取0.5g样品(Te0.1～1%)于250ml锥形杯
For the analysis of constant tellurium, the most widely used is potassium dichromate capacity method. However, the Cr (6+) / Cr (3+) (1.33V) and Te (6+) / Te4 + (1.02V) Redox reaction with Te ~ (4 +) is slow. American ASTM (Annual Book of ASTMStandards, part 12, P423, 1976) provides for the determination of tellurium in copper alloys by the potassium dichromate method. After leaving for 15 minutes, potentiometric titration is performed with Fe2 +. In addition, the method of using nitric acid (1 + 1) direct sample, for the tin-containing copper alloy will precipitation precipitation of stannous acid adsorption tellurium, leading to low results. Therefore, in this paper, the factors influencing the reaction speed of potassium dichromate and tellurium and the reasonable choice of dissolved acid were discussed in this paper. Analysis method Weigh 0.5g sample (Te0.1 ~ 1%) in 250ml conical cup