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  Home > JCE Print > Journal of Chemical Education > Issues > 2008  > July  >
In the Laboratory
Measurement of Henry's Law Constants Using Internal Standards
A Quantitative GC Experiment for the Instrumental Analysis or Environmental Chemistry Laboratory
Chang Ji, Susanne M. Boisvert, Ann-Marie C. Arida, and Shannon E. Day
Department of Chemistry and Biochemistry, Texas State University–San Marcos, San Marcos, TX 78666
Cover
July 2008
Vol. 85 No. 7
p. 969
Abstract
An internal standard method applicable to undergraduate instrumental analysis or environmental chemistry laboratory has been designed and tested to determine the Henry's law constants for a series of alkyl nitriles. In this method, a mixture of the analytes and an internal standard is prepared and used to make a standard solution (organic solvent) as well as a dilute aqueous solution. Both the standard solution and the headspace samples above the aqueous solution at partitioning equilibrium in closed containers are subject to gas chromatographic (GC) analysis. The dimensionless Henry's law constants, Hi, of the analytes can be calculated from the known Hi of the internal standard and the GC peak area ratios. The temperature dependence of Hi may also be studied through the collaboration among several student groups. The experiment is methodologically simple and can be completed in less than four hours. However, the approach is only applicable to compounds that have dimensionless Henry's law constants in the order of 10–3 or less.
Supplement
Student handouts; Instructor notes including the derivation of eq 1
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Citation
Ji, Chang; Boisvert, Susanne M.; Arida, Ann-Marie C.; Day, Shannon E. J. Chem. Educ. 2008, 85, 969.
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Keywords
Analytical Chemistry; Chromatography; Environmental Chemistry; Equilibrium; Gas Chromatography; Gases; Hands-On Learning / Manipulatives; Instrumental Methods; Laboratory Instruction; Physical Chemistry; Upper-Division Undergraduate
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History
Created:
Last Updated:
5/27/2008
6/4/2008
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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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