Sulphur - Symbol S. A yellow non-met­allic element belonging to Group VI of the periodic table. Proton No. 16, Nucleon No. 32 (rhombic), Melting point 112.8^oC. Boiling point 444.74^oC. The element occurs in many sulphide and sulphate minerals. Native sulphur is also found in Sicily and in the USA (obtained by the Frasch process). Sulphur has various allotropic forms. Below 95.6^oC the stable crystal form is rhombic; above this temperature the element transforms into a triclinic form. These crystalline forms both contain cyclic S₈ molecules. At temperatures just above its melting point, molten sulphur is  a yellow liquid containing S₈(as in the solid form). At about 160^oC, the sulphur atoms form chains and the liquid becomes more viscous and dark brown.  

What is Plastic Sulphur? Plastic sulphur is also known as gamma-sulphur, is a tough elastic substance that is formed when molten sulphur is poured into cold water. When sulphur is heated above 113ºC, it melts to form a pale yellow liquid, which becomes darker and more viscous as the temperature is increased. If liquid sulphur is heated to its boiling point of 445ºC, and poured into cold water, plastic sulphur is formed, consisting mainly of long chains of sulphur atoms, bound together by covalent bonds:

Sulphur vapour contains a mixture of S₂ , S₄, S₆, S₈ molecules. Flowers of sulphur is a yellow powder obtained by subliming the vapour. It is used as a plant fungicide. The element is also used to produce sulphuric acid and other sulphur compounds. Sulphur is an essential element in living organisms, occurring in the amino acids cysteine and methionine and therefore in many proteins. It is also a constituent of various cell metabolites, e.g coenzyme A. Sulphur is absorbed by plants from the soil as the sulphate ion (SO₄^2-).

Below: The different phase of Plastic Sulphur. On the right hand side, the top picture is the molten state. While the bottom picture is the final product.