Azufre

SULFUR
AMOS B. SMITH III, UNIVERSITY OF PENNSYLVANIA



To many people, the element sulfur quickly brings to mind unpleasant memories of rotten eggs and unwelcome encounters with skunks.While true that many sulfur-containing compounds, such as mercaptans, thioethers, and disulfides, possess remarkably foul odors, elemental sulfur (S) in pure form is completely odorless, tasteless, andby and large nontoxic.
Referred to in Genesis as brimstone, meaning "a stone that burns," elemental sulfur, which does readily burn in air, has been known since ancient times. The word derives fromsulvere and sulphur (Sanskrit and Latin, respectively). Major sulfur deposits are found in the salt domes ubiquitous to the Gulf Coast of the U.S.; sulfur is the 16th most abundant element in nature.Recovery is by melting with superheated water, a commercial process developed by Herman Frasch in the 1890s and still in use today.
Sulfur is also a major by-product of and can be extracted fromcoal, ores, and minerals such as gypsum, cinnabar, barite, and pyrite (fool's gold). From an economic perspective, most of the world's sulfur production is used to make sulfuric acid (H2SO4),approximately 40 million tons every year just in the U.S. Fertilizers and lead-storage automobile batteries consume a large portion of this supply, with smaller amounts used as insecticides, as dyeing agents,in the manufacture of gunpowder, and to vulcanize natural and synthetic rubbers to impart desirable mechanical properties.
Since sulfur is positioned directly under oxygen in the periodic table,one might suspect relatively simple behavior at the atomic level. This is certainly not the case! Indeed, Jerry Donohue, in his authoritative treatise, "The Structures of the Elements," argues, "Of allof the elements, sulfur presents the most confusion and complexity in this respect." Unlike sulfur's near neighbors, such as N, O, Cl, and Br, or P, As, Se, and Te, which in elemental form exist...