Spectrophotometric catalytic determination of small amounts of rhenium in mineralized rocks and molybdenite

Rhenium is determined by spectrophotometry of the tellurium sol formed by the reduction of tellurate by stannous chloride under the catalytic influence of rhenium. A detailed investigation of the conditions for high sensitivity and stability at lowest concentration levels of rhenium is presented as well as the behavior of twenty-six ions. The method is applied to the determination of some tenths of a part per million or more of rhenium in a milligram aliquot of mineralized rocks, mixtures of molybdenite and rocks, and molybdenite concentrates. The practical quantity limit of detection is 2 x 10^-10 gram of rhenium. Samples are decomposed with a mixture of calcium oxide, calcium chloride, and magnesium oxide. On leaching, the constituents of the sample are precipitated either as calcium salts or as hydroxides except for rhenium and a small amount of molybdenum which pass into the filtrate. Residual molybdenum is removed extraction with 8-quinolinol in chloroform. Better than ninety-five percent recoveries are obtained with two fusions with flux.