Another allotropic form of sulphur is plastic (or amorphous) sulphur. It is also known as gamma–Sulphur, is a tough elastic substance that is formed when molten sulphur is poured into cold water.

Preparation:
Plastic sulphur is prepared by suddenly cooling the molten sulphur (near its boiling point) by pouring it into cold water. Yellow rubbery ribbons of sulphur are formed. They are very soft and can be stretched easily.

Properties:

• It is dark brown rubber–like mass which can be pressed between fingers, hence plastic.
• Its density is 1.92 g/mL.
• It is insoluble in carbon disulphide.
• It melts at 170°C, one chain plastic sulphur polymer contains around one million atoms of sulfur.
• Plastic sulfur is unstable at all temperatures.
• On keeping, it slowly becomes hard and changes into the most stable α–sulphur form.

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