Determination of Copper and Zinc in Brass: Two Basic Methods
Determination of Copper and Zinc in Brass: Two Basic Methods
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黄铜中铜和锌的测定：两种基本方法
DOI：
10.1021/ed100259b
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发表时间：
2010
影响因子：
3
通讯作者：
O. Reynes
中科院分区：
文献类型：
--
作者：
P. Fabre;O. Reynes
本实验采用两种方法测定黄铜中铜和锌的含量。这个实验不需要先进的仪器，使用廉价的化学品，可以很容易地在3小时的高级本科实验室进行。在教学上，说明了溶液中分析化学的基本概念，如pH值，溶解度，络合作用和氧化还原反应。此外，这个实验可以用来介绍合金科学。用浓硝酸氧化黄铜片，产生Cu2+和Zn2+阳离子的溶液。第一种方法是用氢氧化钠对Cu2+和Zn2+阳离子进行酸碱滴定。在pH滴定曲线中观察到相应的氢氧化物络合物的连续沉淀，该pH滴定曲线允许计算Cu 2+和Zn 2+的浓度，从而计算黄铜组合物。第二种方法是基于络合滴定法，分别有和没有络合剂之间的竞争，步骤1和2。在步骤1中，用EDTA滴定铜和锌。在步骤2中，加入硫代硫酸钠掩蔽Cu2+，通过EDTA滴定测定Zn2+浓度。容易获得Cu 2+浓度和黄铜组成。
In this experiment, the concentrations of copper and zinc in brass are obtained by two methods. This experiment does not require advanced instrumentation, uses inexpensive chemicals, and can be easily carried out during a 3-h upper-level undergraduate laboratory. Pedagogically, the basic concepts of analytical chemistry in solutions, such as pH, solubility, complexation, and redox reactions, are illustrated. In addition, this experiment can be used to introduce the science of alloys. Oxidation of brass pieces by concentrated nitric acid yields a solution of Cu2+ and Zn2+ cations. The first method consists in an acid−base titration of Cu2+ and Zn2+ cations by sodium hydroxide. The successive precipitations of the corresponding hydroxide complexes are observed in a pH titration curve that allows the calculation of the concentrations of Cu2+ and Zn2+ and thus the brass composition. The second method is based on complexometric titrations with and without the competition between complexing agents, steps 1 and 2, respectively. In step 1, the copper and zinc together are titrated by EDTA. In step 2, the addition of sodium thiosulfate masks the Cu2+ and the titration by EDTA leads to the determination of Zn2+ concentration. Cu2+ concentration and brass composition are readily obtained.