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  Home > JCE Print > Journal of Chemical Education > Issues > 1998  > September  >
In the Laboratory
Diffusion of CsCl in Aqueous Glycerol Measured by Laser Refraction: A Physical Chemistry Experiment
Simeen Sattar
Department of Chemistry, Bard College, Annandale-on-Hudson, NY 12504

Frank P. Rinehart
Division of Science and Mathematics, University of the Virgin Islands, St. Thomas, VI 00802

Cover
September 1998
Vol. 75 No. 9
p. 1136
Abstract
A physical chemistry experiment for illustrating the effect of solvent viscosity on diffusion coefficients of aqueous electrolytes is described. Diffusion coefficients are measured from projected images of refracted laser light passing through concentration gradients established by layering solvents (water/glycerol solutions) on concentrated electrolyte solutions. Nonlinear regression analysis is performed on data transcribed from the projected skewed Gaussian curves to obtain the standard deviation (s) of the Gaussian at different times. The slope of a graph of s2 versus time is related to the diffusion coefficient D. Values of D are accurate to about 5%. A plot of D versus the reciprocal of solvent viscosity confirms that diffusion slows with increasing viscosity of the medium. A He/Ne laser and easily assembled diffusion cell are the only specialized equipment required.
More Information
*  Citation
 Sattar, Simeen; Rinehart, Frank P. J. Chem. Educ. 1998 75 1136.
*  Keywords
 physical chem, laboratory instruction, diffusion, lasers, laser spectroscopy
*  History
 Created:
Last Updated:		 June 21, 1999
June 24, 2005
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