Experiments in Paper Chromatography I n recent years the conventional undergraduate course in inorganic qualitative analysis has undergone considerable change. Procedures which were once used to identify the individual components of a n "unknown" are now used to illustrate important chemical reactions in solution. At Acadia University a series of paper chromatography experiments has been standardized and introduced into the second year undergraduate laboratory. These complement conventional semi-micro procedures and are used to demonstrate basic physical and inorganic principles, as well as providing an introduction to a useful separation technique. The procedures have been chosen so that the cost of equipment and chemicals is well within the budget of relatively small institutions. Modifications of ascending (one dimensional) and Rutter disc (two dimensional) techniques are employed and ions are identified by dipping the chromatogram into the chromogenic reagent rather than by spraying. I n this way, reagents employed in the experiments can be used repeatedly. As a first step, students determine the Rr values of the individual ions of the following mixtures Ag+, Hgz2+, and P b 2 + Bi3+, Cd2+, C U ~ +Hg2+, , and P b 2 + As3+, Sb3+, and Sn2+ Co2+,Fe3+, and Ni2+ Bag+, Ca2+, and Sr2+ Fez+ and Fe3+ C1-, Br-, and I after which, the identity of the ions present in a given "unknown" is established by semi-micro analysis. Finally, solutions containing the appropriate individual ions are spotted alongside the "unknown" and the chromatographic experiment is performed. The order of appearance and the color of the spots obtained after staining with the chromogenic reagent form the criteria for identification. Students are asked to note the relative ease with which a chromatographic separation can be effected. Although the experiments are introduced with increasing order of complexity, they can be performed while other laboratory work is in progress. Each experiment may be completed easily within a 3-hr laboratory session. This type of investigation appeals to the students and increases their enthusiasm for the course. Copies of the Acadia laboratory manual describing these experiments may be obtained by writing to the authors.
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Journal o f Chemical Education
