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2001
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November
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In the Classroom
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Tested Demonstrations
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The Use of an Inexpensive Laser Pointer to Perform Qualitative and Semiquantitative Laser Refractometry
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Amarílis de Vicente Finageiv Neder, Edgardo García, and Leonardo N. Viana
Instituto de Química, Universidade de Brasilia, C.P. 04478, CEP 70919-970 Brasilia, DF, Brazil
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November 2001
Vol. 78 No. 11
p. 1481
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| Abstract |
In this paper we describe a simple low-cost laser refractometry experiment designed to be executed by inexperienced students or as a classroom demonstration. The purpose of this experiment is to estimate the refractive index (n) of different liquids using a 25-mL beaker and a pocket laser pointer. A pair of chemically related substances for which the refractive indices are found in handbooks is selected, and the relative locations where the laser beams hit a paper screen after being refracted by the two chosen substances and two reference substances are compared. It is recommended that substances with very different n values be used as references, such as water (1.332) and toluene (1.496). In this way any other substance with n within this range can be identified according to the proximity of the refracted beam to one extreme or another. This procedure enables one to distinguish between ethanol (1.361) and 1-propanol (1.385), acetone (1.359) and butanone (1.379), cyclohexane (1.427) and hexane (1.375), ethyl ether (1.353) and tetrahydrofuran (1.405), among other possibilities. An excellent linear correlation between n and the laser beam position on the screen is found, allowing a semiquantitative nestimation for an unknown sample.
See Letter re: this article.
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| More Information |
 Citation |
Neder, Amarílis de Vicente Finageiv; García, Edgardo; Viana, Leonardo N. J. Chem. Educ. 2001 78 1481.
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Keywords |
Demonstrations; Laboratory Equipment / Apparatus; Laboratory Instruction; Lasers / Laser Spectroscopy; Liquids; Qualitative Analysis
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History |
Created:
Last Updated: |
October 8, 2001
August 31, 2005
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Link to Letter added (April 2004).
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| Home > JCE Print > Journal of Chemical Education > Issues >
2001
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November
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1481
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