Earlier the term 'Colloids' was used for a category of substances. However, later, the term colloidal state of matter was preferred. Colloidal dispersions have been classified into different types depending upon the physical state of the dispersed phase and the dispersion medium or the nature of the colloidal particles. They are prepared in the industry or in the laboratory by a number of methods and then purified. Their property has also been studied in detail. Hardy and Schulze made a substantial contribution in studying the coagulation of the colloidds. The protective action of lyophilic colloids was studied by Zsigmondy and he introduced a term, called 'gold number'.

Which of the following does not form a lyophilic colloid?

Stannous chloride solution added to gold chloride solution.

SnCl₂ + AuCl₃ react to form gold sol which is a lyophobic sol.