Based on the extensive insights gained from the acid bake-leach reaction from our previous experiments, a rigorous experimental plan was designed to investigate the effects of time, temperature, particle size, nitrogen flow rate, sulfuric acid concentration and dosage, and reaction surface area on the extraction of Cu and As from a high-quality enargite sample through sulfuric acid baking and leaching. The baking experiments in the temperature range of 170-200 degrees C over 1-4 h revealed almost complete Cu and As extraction after 4 h baking at 200 degrees C, a sulfuric acid to enargite weight ratio (S/E) of 4, nitrogen flow rate similar to 100 mL/min, and particle size P-100= 45 mu m, and no arsenic was lost to the gas phase. The following reaction is suggested for the sulfuric acid baking of enargite: 4Cu(3)AsS(4) + 28H(2)SO(4) = 3CuO center dot CuSO4 + 6CuSO(4) + 2As(2)O(3) + 28H(2)O + 19.5SO(2)(g) + 15.5S Lack of a systematic dependence of reaction rate on particle size and the significant dependence of the rate on sulfuric acid concentration suggest that the rate of the baking reaction is controlled by the internal surface area of cracks at which surface the baking reaction occurs. It is expected that these cracks are formed as a result of a major volume increase during the baking reaction. High nitrogen flow rates encouraged arsenic loss to the gas phase. Decreasing the S/E ratio from 4 to 2 resulted in a decrease in the rate of reaction, while increasing sulfuric acid concentration enhanced the rate. Excess sulfuric acid was found to be necessary for both acceptable reaction rates and also for maximum As retention in the condensed phase. Doubling the reaction surface area did not affect the extraction of Cu and As. (C) 2014 Elsevier B.V. All rights reserved.