During the preparation of colloidal sol by Bredig's are method , traces of alkali `(NaOH " or " Na_2CO_3)` is added to

Options

A. Homogenise the sol
B. stabilize the sol
C. act as peptizing agentact
D. act as coagulating agent

Answer

**Step-by-Step Solution:**

1. **Understanding Bredig's Arc Method**:
- Bredig's arc method is a technique used to prepare colloidal solutions of metals such as gold, silver, and platinum. It involves the electrical disintegration of metal electrodes in a liquid medium.

2. **Role of Alkali**:
- In this method, traces of alkali (such as sodium hydroxide, NaOH, or sodium carbonate, Na2CO3) are added to the solution. The purpose of adding alkali is to stabilize the colloidal sol that is formed during the process.

3. **Stabilization of Colloidal Sol**:
- The addition of alkali helps to prevent the aggregation of colloidal particles, which can lead to the precipitation of the sol. Sodium hydroxide is particularly effective in maintaining the stability of the colloidal sol by providing a suitable pH environment.

4. **Conclusion**:
- Therefore, the correct answer to the question is that traces of sodium hydroxide (NaOH) are added to stabilize the colloidal sol during the preparation using Bredig's arc method.

**Final Answer**: Sodium hydroxide (NaOH) is added to stabilize the colloidal sol.

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