Sulphur is a pale yellow, brittle solid. It exists as a crystalline solid of S8 molecules. The eight sulphur atoms are arranged in a ring so as to form a crown shape. These molecules can stack together in two different ways, so there are two different crystalline forms of sulphur called rhombic and monoclinic, following the arrangements of the atoms within the crystals. Rhombic sulphur is the more stable form. There is also a third allotropic form of sulphur: an amorphous form.
Antoine Laurent Lavoisier (1743-1794) in his Traité Élémentaire de Chimie (Elementary Treatise of Chemistry, 1789) included a list of elements including sulphur. His Methods of Chemical Nomenclature (1787), identified sulphur compounds including sulphuric acid (H2SO4), sulphates, and sulphites.
The British scientist John Dalton (1766 - 1844) in A New System of Chemical Philosophy, published in 1808, revived the atomic theory of matter, adding to it the key idea that different elements had different characteristic atomic weights. He also proposed a system of arbitrary marks for several elements. Sulphur was represented by a cross inside a circle.
Sulphur is found in meteorites, volcanoes, hot springs, and as galena, gypsum, epsom salts and barite. There are three commercially important sources:
- Underground sulphur deposits in the USA, Mexico and Poland. Steam is pumped down to melt the sulphur which is pumped to the surface.
- Oil and natural gas. Desulphurisation of oil and natural gas is an important source of sulphur.
- Sulphur containing ores. Zinc sulphide is roasted in air to produce the metal. Sulphur dioxide produced by the process is used directly in the manufacture of the important industrial chemical - sulphuric acid.