Sulphur

Sulphur is extracted from its underground deposits by the frasch process. Three concentric pipes (pipes arranged one inside another) are sunk deep into the deposits. The following process then follows.

1. Super-heated water (about 170°C) is forced into the deposits through the outermost pipe. This melts the Sulphur.
2. Hot compressed air is forced downwards through the inner pipe. The mixture of hot water, molten Sulphur and hot air forms froth.
3. The froth is forced upward to the surfaces through the middle pipe. It is collected in moulds where the Sulphur solidifies, and the water drains off.

Allotropy is the existence of an element in two or more different physical forms without changing its physical state.

Sulphur has two main allotropes namely:

1. Rhombic Sulphur: It is made by dissolving Sulphur in carbon disulphide and allowing the solution to crystallize.
2. Monoclinic Sulphur: It is made by melting Sulphur and then allowing it to cool. It is transparent and needle shaped.

Other allotropes of sulphur

1. Plastic Sulphur: It is a tough plastic substance that is formed by heating Sulphur to melting point and pouring the melt liquid into cold water.
2. Amorphous Sulphur: It is made by exposing a saturated solution of hydrogen sulphide in distilled water to air. The Sulphur deposits as a white powder.

When a thin continuous stream of hot molten Sulphur is poured into a beaker full of cold water it forms long plastic light yellow ribbons. This is called plastic Sulphur. However, when the molten sulphur is allowed to cool in the evaporating dish a solid crust will form on its surfaces. When the crust is pierced and the molten Sulphur poured out through the holes, monoclinic crystals will form underneath the crust and all the way around the dish. The pale-yellow crystals are needle shaped.

1. Natural Sulphur is yellow in colour. However, other Sulphur are colourless.
2. It is tasteless with a characteristic smell.
3. It is insoluble in water but soluble in carbon disulphide and acetone.
4. It melts at 114°C and boils at 444°C.

2. Combustion of Sulphur: Sulphur burns in air with a blue flame to form Sulphur (IV) oxide (Sulphur dioxide)

S(s) + O₂(g) → SO₂(g)

3. Formation of sulphides: Sulphur combines readily with elements to form sulphides.
4. Reaction with metals: Sulphur combines with metals to form sulphides. It oxidizes the metals by accepting electrons.

Fe(s) + S(s) → FeS(s) 2Cu(s) + S(s) → Cu₂S(s)

5. Reaction with non-metals: Sulphur reacts with carbon at high temperature to form carbon disulphide

C(s) + 2S(s) → CS₂(s)

6. Carbon disulphide is a volatile, colourless liquid with a sweet and pleasant smell. When the mixture of iron and Sulphur is heated in a test tube it glows and a black solid iron (II) sulphide is formed. The Sulphur has oxidized the iron by accepting electrons; it is itself reduced to sulphide ions.

Fe(s) → Fe²⁺(aq) + 2e⁻ S(s) + 2e⁻ → S²⁻(s)

7. Reaction of sulphur with acids: Sulphur is oxidized by hot concentrated sulphuric acid to sulphur dioxide while the acid is reduced to water.

S(s) + 2H₂SO₄(l) → 3SO₂(g) + 2H₂O(l)

8. Sulphur is oxidized by nitric acid to Sulphur dioxide.

S(s) + 6HNO₃(l) → H₂SO₄(l) + 6NO₂(g) + 2H₂O(l)

1. Sulphur is used in manufacturing of sulphuric acid which is used to make fertilizers.
2. It is used in manufacturing of calcium hydrogen sulphite (Ca(HSO₃)₂), Sodium sulphide, and Sulphur dioxide which is used for bleaching straw and wood pulp.
3. It is used in manufacturing of insecticides and fungicides.
4. It is used in making fireworks, explosives and matchsticks heads.
5. It is used in dusting grape vines to prevent and cure fungal diseases.
6. It is used in vulcanization of rubber to make it hard.