Steven W. George and J. Arthur Campbell Harvey Mudd College Claremont, California 91716
Refractive Indices of Some Carbon Compounds as a Function of Temperature
M o s t undergraduate chemistry programs have experiments in which refractive indices of liquids are taken.I Our own program involves issuingunknown liquids to freshmen, who then identify the unknowns. One property, potentially measureable with great precision, is refractive index. Unfortunately, the index is a strong function of temperature. Thermostats can, of course, be used. But we feel something is gained if the refractometer is merely thermostated by tap water, and the student adjusts his value for temperature deviation from published values. We find that the average temperature coefficients in the reference hooks are inadequate. Consequently, we determined the data in Table 1 which we issue to all students. They then use these in identifying their unknowns. The procedure has been effective. Since the data are not readily available in the literaWe are most appreciative of a grant from the NSF Science Course Improvement Program which supported this work in development of laboratory experiments. See, for example, the article directly following this one in THIS JOURNAL, 44, 394 (1967).
ture, we give them here. They agree very well with published values at single temperatures. The data can be issued in plotted form if desired, but we prefer to have the students interpolate or ext,rapolate numerical data. Table I . Refractive index as a function of centigrade temperature (in increasing order at 10' C). Refractive Index ~*0.00021
acetone ethyl alcohol ethyl acetate 3-pentanone n-bulaool 2-methoxy ethanol Garnyl alcohol 1.1 diohloroethsne oyolohexane n-dimethyl farrnarnide oyclo~entanone 1.1.1 triohloroethane ohloroform cis 1.2 diohloroethylene 1.2 diohlomethane carbon tetraohloride 1.1.2 trichlomethane triohioroethylene mesity1ene benzene ethyl benzoate
Volume 44, Number
7,July 7 967
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393
