Question

How is colloidal sulphur in water prepared?

Answer 1

Colloidal sulphur can be prepared in several ways.

(i) By oxidation of hydrogen sulphide:

\[\ce{H2S + Br2 -> S + 2HBr}\]

Bromine water or other oxidising agents like nitric acid or SO₂ can be used.

(ii) By double decomposition:

\[\ce{Na2S2O3 + 2HCl -> 2NaCl + SO2 + H2O + S}\]

(iii) By reacting H₂S with SO₂:

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

In all cases, colloidal sulphur is formed as a result of these reactions, and it remains in suspension in water.