Polarogpraphy of Europium(III) in Acetonitrile in the Presence of Thiocyanate and Halide Ions

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Abstract
Studies were carried out on the polarographic behavior of europium in acetonitrile in the presence of SCN−, Br−, I− and Cl−. Two reduction waves were found in the Eu(III)–SCN− system, one corresponding to the reduction of [Eu(NCS)6]3− and the other to the reduction of [Eu(NCS)2]. In the Eu(III)–Br− system, the reduction potential of Eu(III)–bromide complex species was more positive than that of the [HgBr4]2−/Hg couple. In the Eu(III)–I− system, iodide ions were oxidized in acetonitrile by europium(III). The formation constants of Eu(III)–SCN− system were found to be: logβ6=24.4 for [Eu(NCS)6]3− and logβ2=6.0 for [Eu(NCS)2. The degree of complexation of europium(III) and mercury(II) with bromide ion was also determined.