Explain preparation of sulphur sol and gold sol

CBSE Class 12
1

Explain preparation of sulphur sol and gold sol.

2

Sulphur sol and gold sol are Lyophobic sols and are unstable and are build to colloidal size from small particles by the Condensation method by Chemical reactions.

  1. Oxidation sulphur sol is prepared by passing H2S into SO2
    H2S + SO2 → S (sol) + H2O
  2. Reduction of AuCl3 with formaldehyde gives gold sol.
    AuCl3+ HCHO + 3H2O → Au (sol) + 3HCOOH + 6HCl