In the Laboratory
Notes on Vapor Pressure Equilibria Measurements Albert G. Krieger and John W. Henderson Jackson Community College, Jackson, MI 49201
After reading the article in this Journal (1), we would like to share our experience with a similar experiment based on an earlier article in this Journal (2). Freshman students at our institution use manometers and 24/40 ground-glass distillation apparatus (abandoned by our organic chemistry classes) to measure boiling points at reduced pressures. Distilled water and 2methyl-1-propanol are typical liquids of interest. Students enter their collected data into an Excel template which generates graphs of P vs. T and log P vs 1/T to demonstrate the nonlinear and linear relationships that exist between vapor pressures and temperatures. The templates use the Clausius–Clapeyron equation to determine the normal boiling point and the enthalpy of va-
porization of the liquid studied. The boiling point determined for water is 100 °C and for 2-methyl-1-propanol is 106 °C, within 2° of the CRC Handbook data. We have found that the availability of state-of-the-art equipment need not limit the ability to teach and demonstrate fundamental principles. The Excel template (Macintosh) is available upon request domestically and for the cost of international postage for others.
Literature Cited 1. Kidahl, N.; Berka, L. H. J. Chem. Educ. 1995,72, 258. 2. Schaber, P. M. J. Chem. Educ. 1985, 62, 345.
Vol. 73 No. 11 November 1996 • Journal of Chemical Education
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