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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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Abstract Volume 7 Issue 4 (2002) pp 211-213

Acid–Base Titration: Analysis of Phosphoric Acid Anodizing Solutions. A Problem-Based Learning Approach

Marina C. Koether* and Charles R. Munafo

Department of Chemistry and Biochemistry, Kennesaw State University, Kennesaw, GA 30144
Received April 19,2002. Accepted May 7, 2002

Published online: 7 June 2002

Abstract. Phosphoric acid anodizing solutions are routinely titrated to monitor their concentrations; however, after successive anodizations of aluminum metal, increasing amounts of dissolved aluminum interfere with the neutralization titration. The true concentration of phosphoric acid is determined by a correction factor based on the concentration of the dissolved aluminum, which is determined industrially by flame atomic absorption spectrometry. The academic determination of a correction factor for aluminum as well as copper can be designed as a traditional or a problem-based learning exercise.

Key Words:  Laboratories and Demonstrations; analytical chemistry; acid-base chemistry; problem-based learning; aluminum; copper; phosphoric acid

(*) Corresponding author. (E-mail:

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Issue date: August 2, 2002

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