Salicylate Detection by Complexation with Iron(III) and Optical Absorbance Spectroscopy. An Undergraduate Quantitative Analysis Experiment

Kendra R. Reid and Mark E. Meyerhoff
Department of Chemistry, University of Michigan, Ann Arbor, MI 48109
Jeremy T. Mitchell-Koch
Department of Chemistry, Emporia State University, Emporia, KS 66801
J. Chem. Educ., 2008, 85 (12), p 1658
DOI: 10.1021/ed085p1658
Publication Date (Web): December 1, 2008

Abstract

An experiment for the undergraduate quantitative analysis laboratory involving applications of visible spectrophotometry is described. Salicylate, a component found in several medications, as well as the active by-product of aspirin decomposition, is quantified. The addition of excess iron(III) to a solution of salicylate generates a deeply colored solution whose absorbance can be easily measured. The salicylate content in over-the-counter acne medications and an unknown is determined after construction of a linear calibration curve. Further, the nature of the iron–salicylate interaction can be investigated by using the method of continuous variation (Job's method) to determine the predominant stoichiometry of the complex. This experiment is easily adapted to a wide variety of available instrumentation and has been successfully tested at both the University of Michigan and Emporia State University. It is possible to complete the entire experiment in a single three-hour laboratory period, but splitting it into two sessions allows students to analyze their data as it is collected.

Keywords:

Second-Year Undergraduate

Keywords:

Analytical Chemistry

Keywords:

Hands-On Learning / Manipulatives

Keywords:

Consumer Chemistry
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  • Received: August 03, 2009

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