colloidal solution of gold is prepared by :

Options

A. colloidal mill
B. double decopostion method
C. Bredig 's method
D. peptization

Answer

To prepare a colloidal solution of gold, we can follow these steps:

1. **Understanding the Methods**: First, we need to recognize the different methods available for preparing colloidal solutions. The options given are:
- Option 1: Colloidal mean
- Option 2: Double decomposition method
- Option 3: Bridex method
- Option 4: Peptization method

2. **Identifying the Correct Method**: Among these options, we focus on the Bridex method, also known as the electrical disintegration method or Bridex-Arc method. This method is specifically used for preparing colloidal gold.

3. **Setting Up the Experiment**: In the Bridex method, two metal rods (usually made of gold) are placed in a dispersion medium (like water).

4. **Creating an Arc**: An electric arc is created between the two metal rods. This arc generates heat and causes the gold to vaporize and then condense into fine particles in the dispersion medium.

5. **Formation of Colloidal Gold**: As the gold particles form, they remain suspended in the dispersion medium, resulting in a colloidal solution of gold.

6. **Conclusion**: Therefore, the correct answer to the question is that colloidal solution of gold is prepared by the Bridex method (Option 3).

### Summary of Steps:
- Identify the methods for preparing colloidal solutions.
- Focus on the Bridex method as the correct option.
- Set up the experiment with two gold rods in a dispersion medium.
- Create an electric arc between the rods.
- Observe the formation of colloidal gold in the medium.