<P> In the first step, sulfur is burned to produce sulfur dioxide: </P> <Dl> <Dd> S (s) + O 2 (g) → SO 2 (g) </Dd> </Dl> <Dd> S (s) + O 2 (g) → SO 2 (g) </Dd> <P> or, alternatively, hydrogen sulfide (H 2S) gas is incinerated to SO 2 gas: </P>

Carbon monoxide is formed by the action of concentrated h2so4 on