This investigation deals with the application of high pressure and high-temperature leaching techniques to separate out zinc and copper from the iron constituents of a calcined sulfide ore. An important variable in this study proved to be the concentration of the leaching reagent -- sulfuric acid. The leaching temperature was varied within a range of 250°F to 550°F., and 8 cubic centimeters to 20 cubic centimeters of sulfuric acid in 2000 cubic centimeters of distilled water was employed as the leaching agent concentration. The major equipment utilized for roasting was the fluidized bed and an autoclave for leaching. After the physical and chemical treatments of roasting and leaching of the calcine, the resulting constituents were studied by means of quantitative chemical analysis. Numerical theories were used to correlate the points obtained into continuous functions of the leaching temperature, concentration of sulfuric acid and the recovery percentage. From these curves, it is concluded that the recovery of the impurities in the calcine is proportional to the leaching temperature and the concentration of the leaching agent. However, under certain circumstances, the leaching action causes loss of iron in the calcine, and the minimizing of the loss in leaching is also studied. / Master of Science