Roasting of copper pyrites ores is for the following purposes
a) to burn off sulphur, arsenic, antimony etc. as oxides and convert all the iron and copper to their oxides b) to burn off arsenic, antimony etc. as oxides and burn off sulphur so that enough of it remains to combine with all the copper c) to burn off sulphur partially to leave enough to combine with arsenic, antimony etc. and to convert all the iron and copper to oxides d) to melt arsenic and antimony etc. and remove them by liquation and to burn off sulphur partially to leave enough to combine with copper and iron