Complexometric Titration of Zinc: An Analytical Chemistry Laboratory Experiment

• Published in: Journal of chemical education Vol. 74; no. 12; p. 1463
• Main Author: Novick, S. G
• Format: Journal Article
• Language: English
• Published: Division of Chemical Education 01-12-1997
• Subjects: Second-Year Undergraduate; Hands-On Learning / Manipulatives; Analytical Chemistry; Zinc
• ISSN: 0021-9584; 1938-1328
• DOI: 10.1021/ed074p1463

Complexometric titrations with EDTA have traditionally been performed in undergraduate analytical chemistry courses to determine the calcium or magnesium content of water. These titrations are performed at a basic pH, where the formation constants of Ca-EDTA and Mg-EDTA complexes are high. These types of problems are well-treated in the analytical chemistry textbooks. In contrast, treatment of metal ions whose EDTA complexes occur significantly at low pH (e.g., Zn2+, Fe3+, Cu2+, Ni2+, Pb2+, Al3+) is sparse. An incorrect conclusion can be reached by the student that practical EDTA titrations are only performed at high pH. In addition, widening the window of possible metal ions for complexometric titration affords the possibility of analyzing real world products, such as the cold lozenges discussed in the article.