Pinacyanol as the reagent for the extraction-photometric determination of rhenium (7)

The conditions for the formation and extraction of the ReO4- associate by a cyanine dye - the pinacyanol - with a view of developing an extraction-photometric method for determining rhenium content were studied. The best extractant proved to be a mixture of benzene with acetone (1/1). The maximum of absorption of the pinacyanol perrhenate and the dye is at 602 nm. This means that the interaction of ReO4- with pinacyanol is ionic in character and that a hetero-ligand complex of an ionic associate type is formed in the process. The maximum extraction of pinacyanol perrhenate is in the range from pH 3.5 to 8.5. The benzene-acetone extract of the associate is stable for 20 min. It was found that the proportion of components in the resultant associate is ReO4-/PC=1/1. The molar coefficient of extinction and the complex stability constant, as determined by the Babko method, are equal to epsilonsub(c)=126.000, βsub(c)=0.222x105. These data evidence that pinacyanol perrhenate is not polymerized in the organic phase and is monomeric. The study of the effect of foreign ions upon the accuracy of determination of rhenium by the pinacyanol has shown that some of the ions exert no adverse influence. The proposed method was used to determine rhenium in rhenium and tellurium-rhenium films on a platinum support