Which of the following is not a method of preparation of colloidal solution

Options

A. Electrical dispersion
B. Peptization
C. Coagulation
D. Mechanical dispersion

Explanation

To determine which of the following is not a method of preparation of colloidal solutions, we need to first understand the common methods used to prepare colloids.

### Step-by-Step Solution:

1. **Understand Colloidal Solutions**: Colloidal solutions consist of tiny particles dispersed in a medium. They can be formed through various methods.

2. **Identify Common Methods of Preparation**: The common methods to prepare colloidal solutions include:
- **Dispersion Method**: This involves breaking down larger particles into colloidal size by mechanical means (e.g., grinding).
- **Condensation Method**: This involves the aggregation of smaller particles to form larger colloidal particles (e.g., chemical reactions).
- **Chemical Methods**: Involves chemical reactions that lead to the formation of colloidal particles.

3. **Coagulation**: Coagulation refers to the process where colloidal particles aggregate and settle out of the solution, often induced by the addition of electrolytes. This is not a method of preparation but rather a method of destabilizing a colloidal solution.

4. **Conclusion**: Among the options provided, coagulation is the process that does not prepare a colloidal solution but instead leads to its precipitation. Therefore, the answer is coagulation.

### Final Answer:
Coagulation is not a method of preparation of colloidal solutions.