In this method, small solute particles are condensed to form a dispersed phase particle.
Examples include the following:
1. Chemical methods:
a) By oxidation:
Colloidal sulphur can be obtained by passing oxygen gas through a solution of hydrogen sulphides. In this method any oxidising agent like HNO3, H3Br2 can also be used.
2H2S + O2 → 2H2O + 2S (Sulphur sol)
b) By double decomposition:
A solution of arsenic sulphide is obtained in this method. In this process hydrogen sulphide is passed through Arsenious oxide cold solution in water.
AS2O3 + 3H2S → AS2S3 + 3H2O Arsenic sulphide (sol)
c) By reduction:
A number of metals such as gold, silver, and platinum are obtained in a colloidal state by reacting the aqueous solution of these salts with suitable reducing agents such as formaldehyde, phenylhydrazine, hydrogen peroxide, stannous chloride etc.
2AuCl3 + 3SnCl2 → 3SnCl4 + 2Au (gold sol)
2AuCl3 + 3HCHO + 3H2O → 2Au + 3HCOOH + 6HCl
The gold sol prepared in the reduction of gold chloride solution has a purple colour and is called purple of Cassius.
Frontiers, E. (2022). CHM 232- Physical Chemistry. Afribary. Retrieved from https://afribary.com/works/chm-232-physical-chemistry
Frontiers, Edu "CHM 232- Physical Chemistry" Afribary. Afribary, 03 Jul. 2022, https://afribary.com/works/chm-232-physical-chemistry. Accessed 04 May. 2024.
Frontiers, Edu . "CHM 232- Physical Chemistry". Afribary, Afribary, 03 Jul. 2022. Web. 04 May. 2024. < https://afribary.com/works/chm-232-physical-chemistry >.
Frontiers, Edu . "CHM 232- Physical Chemistry" Afribary (2022). Accessed May 04, 2024. https://afribary.com/works/chm-232-physical-chemistry