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  Home > JCE Print > Journal of Chemical Education > Issues > 1997  > August  >
In the Laboratory
A Simple Undergraduate Concentration Step Experiment
John Cassidy, Fiona Fitzpatrick, and Sean Culhane
Department of Chemistry, Kevin Street, Dublin Institute of Technology, Dublin 8, Ireland
Cover
August 1997
Vol. 74 No. 8
p. 964
Abstract
This experiment is designed to demonstrate the process of diffusion; movement of species under a concentration gradient. By using a solvent immiscible with water containing a chelate (dithizone) which changes color when complexed with a metal, in contact with an aqueous solution of zinc ions, it is possible to mimic a concentration step at the solvent water interface. It is possible to spectroscopically monitor the system if the layers are in a cuvette in a visible spectrometer. Experimentally it can be seen that the absorbance changed with the square root of time, from which the diffusion coefficient of the dithizone may be determined
More Information
*  Citation
 Cassidy, John; Fitzpatrick, Fiona ; Culhane, Sean. J. Chem. Educ. 1997 74 964.
*  Keywords
 Laboratory, Physical Chemistry, Instrumental Methods, Solutions/Solvents, Spectroscopy
*  History
 Created:
Last Updated:		 July 28, 1999
June 23, 2005
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