The widespread use of various substances in the flotation of minerals clogs wastewater, which, poisoning reservoirs, endangers the normal existence of wildlife.

Кинетика растворения и методы фазового анализа соеди­нений сурьмы изучались неоднократно. Для исследова­ния кинетики растворения Sb₂S₃и Sb₂0₃в растворах КОН с целью возможности использования их для фазового анализа были взяты полидисперсные образцы этих соединений сурьмы (чда) ....

Обычно применяемые для разделения окисленных и суль­фидных соединений висмута соляная и азотная кис­лоты не позволяют количественно разделить окисленные и сульфидные минералы висмута ...

The best in refractory stability are the masses consisting of oxides forming solid solutions. The absence of eutectics that cause premature softening and deformation at relatively low temperatures makes solid solutions of oxides a valuable highly refractory material. From this point of view, the regions of solid solutions in the Cr203-Zr02-Si02 system characterized by high melting temperatures are of considerable interest. The existence of ternary solid solutions in this system made us assume the existence of solid solution regions in the double systems Zr02-Si02 and Cr203-Zr02.

The development of modern electrometallurgy raises the question of finding new highly refractory materials that increase the service life and productivity of electric furnaces. The study of the melting temperature dependence on the composition of mixtures of highly refractory materials, especially the determination of the areas of formation of solid solutions with high refractoriness, is one of the ways to find highly refractory materials. Among the existing refractories, chromium ironstone, magnesite, zirconium dioxide, etc. deserve great attention. At present there are already a number of studied systems of chromium oxide with oxides MgO, CaO, Аl₂О₃, ZrО₂. The system of Сг₂О3 — SiО₂ has not been studied yet. Its study was carried out by us in connection with the subsequent study of the ternary system Сг₂О₃ — SiО₂— ZrО₂, which is not only theoretical but also of practical interest in the search for new highly refractory materials.

Among the refractory materials currently in use, chromite iron ore and magnesite deserve special attention. But, as is known, these refractories in their pure form are not stable enough and are destroyed relatively quickly, which causes frequent repairs of the internal lining of smelting furnaces. Therefore, the study of the dependence of the melting temperature on the composition of mixtures of highly refractory materials, in particular the determination of the areas of formation of solid solutions, is one of the ways to find new highly refractory materials. This prompted us to study the melting diagrams of the systems: Сr₂O₃ — MgO и Сr₂O₃ — ZrO₂.

The first literary data date back to 1930, when attempts were made to study the melting diagram of the Сr₂О₃— ZrO₂ system. Having discovered the significant volatility of chromium oxide, the authors abandoned further research. The results of the work are presented in Fig. 1, which shows that the data obtained cannot even be approximate. These data exhaust the literary information on the Сr₂О₃— ZrO₂ system. Believing that the volatility of Сr₂О₃ in itself cannot serve as an obstacle to studying the system, since the composition of each point can be determined by chemical analysis of the fused portion of the samples, after determining the melting point, we decided to study the equilibrium diagram of this system, which is of not only theoretical but also significant practical interest.