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Lab:Allotropes of sulfur

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This experiment demonstrates the preparation and properties of the allotropes of sulfur, and enables students to study the relationship between structure and properties.

Sulfur is heated slowly and steadily from room temperature, so that all the changes in colour and consistency as it melts and eventually reaches boiling point, can be observed. A fresh sample of sulfur is heated to just above the melting point, then allowed to cool and crystallise slowly as monoclinic sulfur. A further sample is heated to boiling point, and the liquid rapidly chilled in cold water to form plastic sulfur.

A separate sample of sulfur is dissolved in a warm solvent, and the solution allowed to cool and evaporate, leaving crystals of rhombic sulfur.

All the observed changes in properties can be related to the different molecular structures of the three solid forms of sulfur, and to the changes in structure as the temperature of liquid sulfur is gradually raised.


Health & Safety checked, August 2008

Web Links

An extensive and all-encompassing review of the allotropy of sulfur can be consulted at:


This experiment has been reproduced from Practical Chemistry. Details can also be found at: