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A laboratory experiment is presented for the upper-level undergraduate physical chemistry curriculum in which the ternary phase diagram of water, 1-propanol and n-heptane is measured using proton nuclear magnetic resonance (NMR) spectroscopy. The experiment builds upon basic concepts of NMR spectral analysis, typically taught in the undergraduate organic chemistry curriculum, applying them to the study of phase behavior, a traditional basic topic of thermodynamics. (Contains 3 figures.)

The application of supercritical (sc) fluid technology requires a thorough understanding of thermodynamic phase behavior. Therefore, an experiment in the physical chemistry laboratory that allows direct control and visual observation of P-V-T phase behavior has educational value for students. Students develop an experience-based understanding of how phase behavior can be manipulated. Laboratory experiments involving sc fluids also provide valuable training for students concerning the proper and safe handling of compressed fluids.

The objective of this article is to communicate and discuss a classroom exercise that engages students as a team to develop an intuitive understanding of the P- V- T phase behavior of a pure fluid. The classroom exercise requires the availability of four one-half hour periods. Since the exercise draws on the students' visualization and imagination skills, each period is actually a rather intense experience and should probably not exceed the half-hour period by too much. The author hopes to have stimulated the reader to further think about how to best confront the students with this challenging thermodynamic subject and how to best guide them through the learning process.