Research is conducted to determine the effect of production parameters on osmium extraction during leaching roasting cinders containing osmium and rhenium from copper production cakes with water, hydrogen peroxide and various oxidizing agents. The main goal is to maximize osmium extraction into the gas phase for subsequent conversion into osmium sulfide. Material leaching is performed within a unit assembled for this purpose. During leaching osmium is distributed among the leaching products: gas phase, leaching solutions, and leaching cakes. Results of the work and their novelty: the effect of temperature and duration on the extraction of osmium during water leaching of cinder is studied. The activity of 11 oxidizing agents during cinder leaching is investigated; an oxidizing agent close to the optimum is selected for transferring osmium tetroxide into the gas phase and its absorption by sodium alkali. Oxidizing agent consumption during cinder leaching in various regimes is determined.