<unk>  (also sulphur<unk>  is the chemical compound with the formula<unk> . This important gas is the main product from the combustion of<unk>  compounds and is of significant environmental concern. <unk>  is often described as the "smell of burning<unk> " but is not responsible for the smell of rotten eggs.<unk>  is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain<unk>  compounds, their combustion generates<unk> .  Further oxidation of<unk> , usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.
Sulfur dioxide
Carbon suboxide
Xylene
Ether
Nitrogen oxide
Acrolein
Carbon dioxide
Peroxide