which one of the following is not used for preparing lyophilic sols ?

Options

A. starch
B. Gum
C. Gelatin
D. Metal sulphide

Answer

To determine which of the following substances is not used for preparing lyophilic sols, we need to understand what lyophilic sols are and how they differ from lyophobic sols.

### Step-by-Step Solution:

1. **Define Lyophilic Sols**:
- Lyophilic sols are colloidal systems where the dispersed phase (particles) has a strong affinity for the dispersion medium (usually water). This means that these particles can easily dissolve or mix in the solvent.

2. **Identify Examples of Lyophilic Sols**:
- Common examples of substances that form lyophilic sols include:
- **Starch**: A polysaccharide that readily dissolves in water to form a colloidal solution.
- **Gum**: A natural polymer that also dissolves well in water, forming a colloidal solution.
- **Gelatin**: A protein derived from collagen that forms a colloidal solution when mixed with water.

3. **Analyze the Options Given**:
- The options provided are:
- **Starch**: Used for preparing lyophilic sols.
- **Gum**: Used for preparing lyophilic sols.
- **Gelatin**: Used for preparing lyophilic sols.
- **Metal Sulphide**: Typically does not have an affinity for the dispersion medium and is known to form lyophobic sols.

4. **Conclusion**:
- Since starch, gum, and gelatin are all used to prepare lyophilic sols, the only option that does not fit this category is **Metal Sulphide**. Metal sulphides are generally considered lyophobic because they do not have a strong affinity for the dispersion medium.

### Final Answer:
**Metal Sulphide is not used for preparing lyophilic sols.**

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