A simple, versatile, and low-cost version of a qualitative ion migration experiment is presented,
which needs a minimum amount
of chemicals and can be performed by inexperienced students. In the experiment cations and anions
(preferably colorless or faintly
colored) migrate toward one another and on combination produce insoluble and strongly colored compounds.
A strip of filter paper
supported on a glass plate and soaked with an electrolyte solution (NH4NO3)
is used as migration medium.
The paper is spotted with
a suitable pair of solutions containing the reactive ions using a capillary pipet. A tension of 30-V dc is
applied using graphite
electrodes. The result is observed within 10 minutes: at the meeting point of the two ions the reaction
product precipitates,
forming a sharp colored spot on the filter paper. The following ion combinations have been used successfully:
Pb2+/I-, Hg2+/I-, Ag+/I-,
Pb2+/CrO42-, Cu2+/[Fe(CN)6]4-,
Fe3+/[Fe(CN)6]4-, Fe2+/[Fe(CN)6]3-, and
Zn2+/[Fe(CN)6]3-.
More Information
Citation
Bessler, Karl E.; Campos, Daniel de O. J. Chem. Educ.1999 76 1516.
Keywords
Aqueous Solution Chemistry; Electrochemistry; Inorganic Chemistry; Introductory / High School Chemistry; Laboratory Instruction
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