CHM 232- Physical Chemistry

13 PAGES (972 WORDS) Chemistry Study/Lesson Note
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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.

ž  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.

ž  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.

ž  2AuCl3 + 3SnCl2 → 3SnCl4 + 2Au (gold sol)

ž  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.


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Frontiers, E. (2022). CHM 232- Physical Chemistry. Afribary. Retrieved from

MLA 8th

Frontiers, Edu "CHM 232- Physical Chemistry" Afribary. Afribary, 03 Jul. 2022, Accessed 08 Aug. 2022.


Frontiers, Edu . "CHM 232- Physical Chemistry". Afribary, Afribary, 03 Jul. 2022. Web. 08 Aug. 2022. < >.


Frontiers, Edu . "CHM 232- Physical Chemistry" Afribary (2022). Accessed August 08, 2022.