Abstract
A new method of detecting zinc ion has been investigated. The present method using diethylaniline and potassium ferricyanide is inevitably affected by many various oxidants. In order to improve the shortcoming, thiourea and rhodamine B have been adopted by the author in the place of diethylaniline; that is, in the presence of thiourea, zinc ion with potassium ferricyanide does not produce yellowish brown zinc ferricyanide, but white zinc ferrocyanide, which adsorbs rhodamine B and exhibits a purple coloration. This purple precipitation is specific for zinc ion only.
The recommended procedure is as follows; to a neutral or slightly acidic test solution which is supposed to contain zinc ion, 1M thiourea solution and 0.5% rhodamine B solution are added and stirred well, and 0.05M potassium ferricyanide solution is added drop by drop, with constant agitation. When zinc ion is present, a purple precipitate is formed.
This method also can be applied to in spot test, when the limit of identification for zincion by this method is 2γ per drop of the test solution.
