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ERIC Number: EJ918558
Record Type: Journal
Publication Date: 2010-Aug
Pages: 2
Abstractor: As Provided
Reference Count: 11
ISBN: N/A
ISSN: ISSN-0021-9584
Determination of Copper and Zinc in Brass: Two Basic Methods
Fabre, Paul-Louis; Reynes, Olivier
Journal of Chemical Education, v87 n8 p836-837 Aug 2010
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 Cu[superscript 2+] and Zn[superscript 2+] cations. The first method consists in an acid-base titration of Cu[superscript 2+] and Zn[superscript 2+] 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 Cu[superscript 2+] and Zn[superscript 2+] 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 Cu[superscript 2+]and the titration by EDTA leads to the determination of Zn[superscript 2+] concentration. Cu[superscript 2+]concentration and brass composition are readily obtained.
Division of Chemical Education, Inc and ACS Publications Division of the American Chemical Society. 1155 Sixteenth Street NW, Washington, DC 20036. Tel: 800-227-5558; Tel: 202-872-4600; e-mail: eic@jce.acs.org; Web site: http://pubs.acs.org/jchemeduc
Publication Type: Journal Articles; Reports - Descriptive
Education Level: Higher Education
Audience: N/A
Language: English
Sponsor: N/A
Authoring Institution: N/A