In the process of hydrometallurgical and pyrometallurgical production of antimony at the Kadamzhai antimony plant of the Kyrgyz Republic, large-tonnage waste was generated: tailing sand, matte, slag, off-balance ore, cakes, furnace fragments, and electrolytes in salt warehouses. The waste cake is poorly studied; accordingly, the elemental and phase compositions of antimony cake have not been established. In this regard, it was noted that antimony in the cake occurs in the form of calcium antimonate and antimony hydroxide. The content of antimony in the mine tailings cakes is from 3.53 to 4.4%, with a high content of iron (27.5%) and sodium (8.86%). Based on the established elemental and phase compositions, a chemical matrix of antimony cake was compiled. The equilibrium compositions were calculated and the concentration distribution of the main elements of the cake (Fe, Na, Si, Sb) and their compounds in the gas phase was found depending on the temperature of the destruction of the solid phase. It was found that condensed antimony oxides are formed in the range of 1098 -1348 K. Taking into account the range of temperatures for decomposition of the solid phase, a two-stage smelting of antimony cake is proposed (melting and cupellation). The conversion of antimony cake sulfides from the gas phase into a solution was carried out based on a study of the system: antimony sulfide-manganese (IV) dioxide-sulfuric acid -sodium chloride. The pH value and the redox potential (Eh) of the solution were calculated. It is noted that the sulfur compounds of antimony from the cake are converted to antimony oxychloride with the formation of antimony (III) oxide in an alkaline medium. The use of sodium chloride as a chlorinating agent of antimony sulfur compounds does not lead to the formation of toxic phosgene and hydrogen sulfide; in the solid phase, elemental sulfur is released, which is important for minimizing the technogenic load of pollutants on the environment.