Preparation of Colloidal Gold

Colloidal gold is prepared by Bredig's Arc Method.

Bredig's Arc Method

The method involves the following steps:

1. A small quantity of gold is placed in an arc, and a current is passed through it.

2. As a result of the current, the gold is vaporized.

3. The vapor so produced is allowed to pass through a cold surface, which condenses the vapor.

4. The condensed gold particles are collected in a vessel containing a suitable stabilizer.

5. The gold particles thus obtained are in the range of 10-100 nm.

6. The size of the particles can be controlled by varying the distance between the arc and the collection vessel.

7. The stabilizer used for colloidal gold is usually a protein or a polymer, which prevents the particles from agglomerating.

8. The color of the colloidal gold depends on the size of the particles, which in turn depends on the distance between the arc and the collection vessel.

9. The smaller the size of the particles, the more intense is the color.

10. Colloidal gold has various applications in the fields of medicine, biology, and materials science.

11. It is used for staining biological samples, as a contrast agent in electron microscopy, and as a catalyst in various chemical reactions.

Thus, Bredig's arc method is an effective way of preparing colloidal gold, which has numerous applications in various fields.

By mechanical dispersion