MadSci Network: Chemistry

Re: How do I determine the amount of copper in brass?

Date: Fri Jan 28 22:19:05 2000
Posted By: Xianlong Wang, Grad student, Chemistry, Nanjing Univ.
Area of science: Chemistry
ID: 948715729.Ch

The copper can be determined by the indirect iodine method. In the procedure you described, is most important step is listed. After adding acetic acid to the solution, an excess of KI should be added to reduce Cu2+ ions quantitively. I2, the oxided product, can be titrated by the sodium thiosulfate. The molar relationship between Cu and sodium thiosulphate is 1:1.

A similar process involves following:

The reaction equations:

2Cu2+ + 4I- ===> Cu2I2 + I2
2S2O3 2- + I2 ===> 2I- + S4O6 2-
Cu2I2 + 2SCN- ===> Cu2SCN2 + 2I-

Reference:Chemical Analysis & Instrumental Analysis Experiments, Ed. by Qi Qin et al. Nanjing Univ. Press, 1992.

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