Experimental determination of the reaction chalcopyrite + sulfur = pyrite + bornite from 350 to 500° C

The fugacity of sulfur along the curve representing the univariant equilibrium assemblage, chalcopyrite + bornite + pyrite + vapor, has been determined by the electrum tarnish method (1). The conditions of the equilibrium may be expressed by the equation (TP) - /°s ₂ (T, 1 atm) = -50,730 + 56.95T (cal.) (350 - 500° C) (T in °K). With gentle curvature, the line may be extended upward to the invariant point at 568° C, which represents the assemblage chalcopyrite + bornite -j- pyrite + liquid + vapor (8).