The Guide to Rocks and Minerals

In focus: Sulphur

Chemical Composition: S
Group: Native element
Colour: Yellow, Orange, White
Streak: none
Hardness: 1.5-2.5
Density: 2-2.1
Luster: Resinous
Cleavage: Imperfect

Sulphur (S) is a soft, bright yellow element which is solid at room temperature and which occurs naturally. Sulphur (from Latin sulfur or sulpur) was known in ancient times but the name itself is probably from the Arabic sufra, meaning 'yellow'. Until the late 18th century sulphur was thought to be a compound. It was only in the late 1770s that the scientist Antoine Lavoisier managed to convince the chemists of his day that it was in fact an element.

Although not a compound, Sulphur could certainly deserve to be put in this section simply because its many interesting properties and economic importance are as great as any conmpound. One of these properties is its complex crystal structure. Depending on the specific conditions and the sulphur allotropes (different forms of the same element in the same physical state) sulphur can form several different structures. Rombic and monoclinic are the most common crystal structures of allotrope S8. But sulphur has many allotropes besides S₈. For example, it can exist as S₇ (where it loses the characteristic yellow colour), S₁₂ or S₁₈. At high temperature sulphur produces long polymer chains which are responsible for its high viscosity.

In its natural form, sulphur can be found near hot springs and in volcanic regions. Large sulphur deposits are found along the Pacific's 'Ring of Fire'. There are currently sulphur mines in Indonesia, Chile and Japan. Sicily (Italy) is also a large producer of naturally occuring sulphur. Large deposits of natural sulphur also exist in other parts of Europe and Asia. These are predominantly in the form of evaporates (material precipitated by evaporation). Evaporates are believed to come from either sulphate minerals, particularly from gypsum or precipitated by the action of anaerobic bacteria. Fossil-based sulphur deposits are the basis of commercially produced sulphur in number of countries including Poland, Russia and the United States.

Sulphur combines with many minerals to create a large number of naturally occurring sulphur compounds. These include the above-mentioned gypsum (calcium sulphate), pyrite (iron sulphate), galena (lead sulphate), barite (barium sulphate) just to mention a few. Sulphur also readily associates with gasses. When burned, sulphur combines with oxygen to give rise to sulphur dioxide. Further oxidation will lead to the production of sulphur trioxide which when combined with water produces sulphuric acid (H₂SO₄). The latter compound is largely responsible for sulphur being one of the most important raw materials in industry.

Mineral uses

Sulphur is also used in batteries, detergents, the vulcanization of rubber, fungicides, i.e. skin-care soaps, and in the manufacture of phosphate fertilizers.
Because of its flammable nature, sulphur is used in the production of matches, gunpowder, and fireworks.
Principal uses for sulphuric acid include ore processing, fertilizer manufacturing, oil refining, waste water processing, and chemical synthesis.
Sulphates (compounds that contain the sulphate ion SO₃^2-.) are used as a preservative in wine, dried fruit and and dried potato products
In medicine Magnesium Sulphate, better known as Epsom salts, can be used as a laxative
Elemental sulphur crystals are commonly sought after by rock collectors for their brightly-coloured polyhedron shapes.
In the late 18th century, furniture makers used molten sulphur to produce decorative inlays in their products. But because toxic sulphur dioxide is produced when heating sulphur to the high temperatures required the process was soon abandoned.
Nowadays molten sulphur is still used occasionally for setting steel bolts into drilled concrete holes where high shock resistance is desired for floor-mounted equipment attachment points.

The use of sulphur and sulphur compounds is so widespread in the modern world that it is impossible to list all the uses in that section.

Identification

At room temperature, sulphur is a soft, bright yellow material. It has only a faint odour similar to that of matches. Sulphur is insoluble in water but soluble in carbon disulphide and to a lesser extent in other organic solvents such as benzene and toluene. It burns with a blue flame that emits sulphur dioxide, notable for its peculiar suffocating odour. A noteworthy property of sulphur is its viscosity in its molten state. Unlike most other liquids, temperature increases to above 200^oC lead to the formation of polymer chains. The molten sulphur also becomes dark red above this temperature. However, after a specific temperature is reached, the viscosity is reduced because there is enough energy to break the chains.

_______________________________
Home	\|	Shopping	\|	Database