Which of the following is not a method of removing impurities from a colloidal sol ?

Options

A. Electrodialysis
B. Ultrafiltration
C. Ultra centrifugation
D. Distillation

Answer

To determine which method is not used for removing impurities from a colloidal sol, we can analyze the methods typically employed for this purpose.

### Step-by-Step Solution:

1. **Understanding Colloidal Sols**:
- Colloidal sols are mixtures where tiny particles are dispersed in a medium. These particles can sometimes contain impurities that need to be removed to ensure stability.

2. **Identifying Methods to Remove Impurities**:
- Common methods used to remove impurities from colloidal sols include:
- **Electrodialysis**: This method uses an electric field to drive ions through selective membranes, effectively removing impurities.
- **Ultrafiltration**: This technique uses a membrane to separate particles based on size, allowing smaller impurities to pass through while retaining the colloidal particles.
- **Ultracentrifugation**: This method involves spinning the colloidal solution at high speeds to separate particles based on their density.

3. **Analyzing the Options**:
- The question asks which method is NOT used for removing impurities from colloidal sols.
- Among the methods listed, **distillation** is a process that separates liquids based on their boiling points and is not applicable for removing impurities from colloidal sols.

4. **Conclusion**:
- Therefore, the method that is not used for removing impurities from a colloidal sol is **distillation**.

### Final Answer:
- The method that is not used to remove impurities from a colloidal sol is **distillation**.