The procedure allows students to carry out a diversity of identification reactions of metal ions in a very short time, getting acquainted with their chemical behavior while dealing with "real-life samples", and this is interesting from a pedagogical point of view. Furthermore, sample size or shape do not affect results, the only requirement being ease of handling. Students are asked to estimate the sensitivity of each test. If the migration of the metal ion from the sample surface to the electrolyte-impregnated paper occurs under controlled conditions, the minimum concentration of ions that is re-
quired to produce a perceptible color can be calculated from the number of coulombs passed between the electrodes. Standard disks of metals can be employed for this purpose, and the pressure applied between the two electrodes can be controlled with the aid of an inexpensive clamp. In Table 2 is shown the sensitivity of the tests used for the identification of each ion and the references to the literature. Acknowledgrnenf
The authors wish to thank Eleonora Scoseria for his help with translation and Daniel Ettlin for his cooperation.
Volume 67 Number 8
August 1990
707
