Sulfur dioxide
Sulfur dioxide is primarily produced for sulfuric acid manufacture (see contact process). In the United States in 1979, 23.6 million metric tons (26,014,547 US short tons) of sulfur dioxide were used in this way, compared with 150 thousand metric tons (165,347 US short tons) used for other purposes. Most sulfur dioxide is produced by the combustion of elemental sulfur. Some sulfur dioxide is also produced by roasting pyrite and other sulfide ores in air.