Spectrophotometric determination of rhenium with 4-methylnioxime

Abstract

A simple method applicable to the spectrophotometric determination of less than 0.001% to more than 1.0% of rhenium in molybdenite concentrate and in “molybdenite roaster flue dust” has been developed. Interfering elements commonly found in these materials are removed in three operations: evaporation with hydrochloric acid, precipitation of hydrous oxides with ammonia, and formation of organometallic compounds with ethyl xanthate and chloroform extraction. The method is based on the formation of a soluble, stable, yellow-green rhenium-4-methylnioxime chelate where rhenium VII is reduced by tin II chloride in a dilute hydrochloric acid solution in the presence of 4- methylnioxime (4-methyl-1:2-cyclohexanedionedioxime). The colour develops in less than 5 min and the chloroform extract shows a maximum absorption at 436 mμ. The calibration curve conforms to Beer's law. The molar extinction coefficient for rhenium-4-methylnioxime is about 6.89 × 10 4 as compared to less than 4.5 × 10 4 reported for other methods for rhenium.