The Highest Oxide of Rhenium

Abstract

IN the course of an investigation of the oxides of rhenium in progress in these laboratories, we have sought to repeat the preparation of the highest oxide described by I. and W. Noddack,¹ Re₂O₈, which was obtained by them on heating the heptoxide below 150° in a stream of oxygen. The yellow heptoxide used in the Noddacks' preparations melted at 220° and gave rise to a white sublimate at 150° described as Re₂O₈ and possessing the property of decolorising acidified potassium permanganate. The melting point of our specimens of heptoxide has invariably been about 300°,² and this material failed to give any evidence of a white sublimate when heated in a stream of oxygen to temperatures below its melting point. Moreover, quantitative experiments repeatedly showed that its formation was unattended by any increase in weight. The sublimate was identical in crystalline form with the heptoxide, was decidedly yellow, and melted to a yellow solid, also indistinguishable from the heptoxide.