- By Muneeb Jamal
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Allotropes Of Sulphur:
Sulpher exists in many allotropic forms however the important three allotropic forms of sulphur are as under.
1. Rhombic Sulphur:
It is an allotropic form of sulphur which is stable below 96 one molecule of rhombic sulphur contains 8-atoms i-e 8g. The crystal of rhombic sulphur has octahedral structure.
Rhombic sulphur is prepared by dissolving ordinary powdered sulphur in carbon disulphide (cs2) the saturated solution is then filtered and the filtrate is allowed to evaporate at room temperature. After evaporating Cs2, crystals of rhombic sulphur are obtained crystal of rhombic sulphur.
- It is consist of pale yellow crystals.
- It melts at 110℃.
- It is insoluble in water and soluble in carbon disulphide.
- It is stable at room temperature.
- Its specific gravity is 208g/cm3.
2. Monoclinic Sulphur:
It is the allotropic form of sulphur which is stable between 96 to 119 a molecule of monoclinic sulphur consists of eight sulphur atoms i-e 8g, but is different from rhombic sulphur in the arrangement of atoms.
Ordinary sulphur is mulled in a china dish with slow heating. The molten sulphur is allowed to cool down until a crest is formed at the surface, the holes are made in the crest by glam rod and molten sulphur is powered out, the crest is also removed and at the bottom, needle shaped crystals of monoclinic sulphur are left.
- It is stable from 96℃-119℃.
- Its melting point is 119℃.
- It is soluble in carbon disulphide.
- Its one molecule consist of 8 atoms.
- It is found as pale yellow needle shaped crystals.
3. Plastic Sulphur:
It is a non crystalline allotropic form of sulphur, it can be stretched like a rubber, it is unstable and changes into rhombic sulphur on slight heating even at room temperature it also changes.
Heat some powdered sulphur in a test tube, it will melt into a yellow liquid, on further heating it changes into a dark red molten mars. Throw this molten maxs into cold water. On solidification the plastic sulphur is obtained.