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  Home > JCE Print > Journal of Chemical Education > Issues > 2008  > December  >
In the Laboratory
Salicylate Detection by Complexation with Iron(III) and Optical Absorbance Spectroscopy
An Undergraduate Quantitative Analysis Experiment
Jeremy T. Mitchell-Koch
Department of Chemistry, Emporia State University, Emporia, KS 66801

Kendra R. Reid and Mark E. Meyerhoff
Department of Chemistry, University of Michigan, Ann Arbor, MI 48109

Cover
December 2008
Vol. 85 No. 12
p. 1658

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.
Supplement
Student handouts; Instructor notes
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Contents
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Citation
Mitchell-Koch, Jeremy T.; Reid, Kendra R.; Meyerhoff, Mark E. J. Chem. Educ. 2008, 85, 1658.
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Keywords
Analytical Chemistry; Consumer Chemistry; Coordination Compounds; Drugs / Pharmaceuticals; Hands-On Learning / Manipulatives; Laboratory Instruction; Quantitative Analysis; Second-Year Undergraduate; UV-Vis Spectroscopy
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History
Created:
Last Updated:
10/24/2008
11/7/2008
 Caution! 
Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations.
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