The cup was then attached to the platinum hook in the TGA oven. The oven was then flushed continuously with pure nitrogen and was heated to a preset temperature at a rate of 15 ◦C/min. When the desired temperature was reached the four-way valve was switched and the air/nitrogen mixture was allowed to enter the reactor, starting the reaction. During the experiment the weight of the sample, the sulfur dioxide concentration in the gas leaving the reactor and the temperature of the reactor were recorded. During a number of experiments the air/nitrogen mixture was fed to the reactor during the temperature ramp. Sieve fractions of reagent grade copper sulfide (Cu2S) and reagent grade copper sulfide (CuS) (−100 mesh) were used during the experiments. The Cu2S (originally −325 mesh) was sieved using 32, 38, and 45 m sieves