Question

Colloid of gold is prepared by striking an electric arc between gold electrodes kept in water.

1. What is this method known as? Why is it regarded as a dispersion method?

2. What is the charge of gold sol? How do particles acquire this charge?

Answer 1

1. Bredig’s arc method. This process involves dispersion as well as condensation. When an electric arc is struck between the metal electrodes immersed in the dispersion medium, due to the intense heat produced the metal gets dispersed by vapourisation which then condenses to form particles of colloidal size.

2. Negative change. Due to electron capture by gold sol particles during electrodispersion of gold.