Purple of cassius is a colloidal sol of

Options

A. silver
B. platium
C. gold
D. iron

Answer

To answer the question "Purple of Cassius is a colloidal sol of," we can break down the solution into several steps:

### Step-by-Step Solution:

1. **Understanding Purple of Cassius**:
- Purple of Cassius is a well-known colloidal solution that is primarily associated with gold. It is formed by the colloidal dispersion of gold particles.

2. **Composition**:
- The colloidal sol of Purple of Cassius is made by mixing gold chloride (AuCl3) with a reducing agent, often stannous chloride (SnCl2). This reduction process leads to the formation of gold nanoparticles.

3. **Color of the Colloidal Sol**:
- The unique purple color of the solution comes from the size and shape of the gold nanoparticles. The optical properties of these nanoparticles give rise to the characteristic purple hue.

4. **Conclusion**:
- Therefore, we conclude that Purple of Cassius is a colloidal sol of gold.

### Final Answer:
Purple of Cassius is a colloidal sol of **gold**.

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