Which one of these is a lyophobic sol?

Options

A. Gelatin
B. Starch
C. Sulphur
D. Gum arabic

Answer

To determine which one of the given options is a lyophobic sol, we first need to understand the definitions and characteristics of lyophilic and lyophobic sols.

### Step-by-Step Solution:

1. **Understanding Lyophilic and Lyophobic Sols**:
- **Lyophilic Sols**: These sols have a good affinity between the dispersed phase (dp) and the dispersion medium (dm). They are easy to prepare and are stable. Examples include starch, gelatin, and egg albumin.
- **Lyophobic Sols**: These sols have little to no affinity between the dispersed phase and the dispersion medium. They are difficult to prepare and are less stable. Examples include metal sulfides, metal hydroxides, and certain inorganic colloids.

2. **Identifying the Options**:
- If we have a list of substances, we need to categorize them as either organic (lyophilic) or inorganic (lyophobic).
- Organic substances like starch, gelatin, and proteins typically form lyophilic sols.
- Inorganic substances such as Fe(OH)₃, As₂S₃, and metal sulfides are examples of lyophobic sols.

3. **Analyzing the Given Options**:
- Look for substances that are inorganic in nature, as these are likely to be lyophobic.
- For example, if one of the options is sulfur (S) or a metal hydroxide like Fe(OH)₃, these would be classified as lyophobic.

4. **Conclusion**:
- After analyzing the options, the lyophobic sol can be identified based on the lack of affinity between the dispersed phase and the dispersion medium.

### Final Answer:
The lyophobic sol among the given options is typically an inorganic compound, such as Fe(OH)₃ or As₂S₃.