Thermal and structural study of the phase transformations of the tellurites of trivalent iron and chromium

Abstract

The thorough and complete extraction of the basic metals, as well as of the metalloids such as selenium and tellurium, is unthinkable without knowledge of the thermal and structural properties of their respective compounds. Selenium and tellurium are finding ever increasing applications. It is known that they are contained most often in the sulphide minerals, and in the main they are associated with the heavy non-ferrous metals. Selenium and tellurium are concentrated in the intermediate slimes from the electrolysis of copper and nickel or in the wastes from lead-zinc production. Contemporary methods for processing the intermediate slimes involve an oxidative or oxidative-sublimative roasting process with subsequent hydrochemical extraction of the valuable components. Literature reports on the behaviour of the selenides and tellurides (basic selenium- and tellurium-containing compounds in the intermediate slimes) in the roasting process and on the thermal stability of selenites are incomplete, and those on tellurites and tellurates are almost non-existent. For that reason investigation of the thermal behaviour of selenium- and tellurium-containing materials appears to be a pressing problem. This work is devoted to clarifying one of the questions in this many-sided problem-investigation and calculation of the melting temperatures as well as the enthalpies and entropies of such substances. PHASE STATE OF THE TELLURITES