Question

Describe a chemical method for the preparation of sol of sulphur in water. 

How is the following sol (in water) prepared?

Sulphur

Answer 1

Method: A chemical method of oxidation is used for preparing sulphur sol.

Procedure: Hydrogen sulphide gas (H₂S) is passed through a solution of sulphur dioxide (SO₂) in water.

A red colloidal sol of sulphur is formed by the following reaction:

\[\ce{2H2S + SO2 -> 3S (Colloidal) + 2H2O}\]

The sulphur precipitated in this reaction remains in the colloidal state and forms a milky sol.

This is an example of oxidation of a gas to form a colloid.