In the Laboratory edited by
Cost-Effective Teacher
Harold H. Harris University of Missouri—St. Louis St. Louis, MO 63121
A Simple Solution for Leaking Polarimeter Cells Gene A. Hiegel Department of Chemistry and Biochemistry, California State University, Fullerton, Fullerton, CA 92834-6866;
[email protected] Polarimeter cells normally consist of a glass tube with each end closed by a glass window, which is held in place by a threaded end cap containing a gasket to keep the window away from the end cap. Glass-to-glass contact between the tube and window is sufficient to contain viscous organic liquids or aqueous solutions for the duration of an optical rotation measurement. However, we found that the methanol solutions used with the resolution of α-methylbenzylamine experiment (1) often leaked through the glass-to-glass seal. A simple solution for this leaking problem is to coat both sides of the windows with a silicone oil solution. We used the inexpensive and readily available product for waterproofing automobile windshields known as Rain-X. A few drops of
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Rain-X were placed on a small piece of soft cloth, and the windows were immediately rubbed on both sides with the cloth. Any visible film was wiped off the windows with a dry cloth. Periodic treatment is necessary to restore the surface properties imparted by the silicone oil. Polarimeter cells with windows treated this way did not leak when used in a normal manner by the students and did not affect the results of the experiment. Literature Cited 1. Gilbert, J. C.; Martin, S. F. Experimental Organic Chemistry, 2nd ed.; Saunders: New York, 1998; pp 190–193.
Journal of Chemical Education • Vol. 78 No. 5 May 2001 • JChemEd.chem.wisc.edu
