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 need to understand the characteristics of lyophobic and lyophilic sols.

### Step-by-Step Solution:

1. **Definition of Lyophobic Sols**:
- Lyophobic sols are "solvent-hating" sols. They have very little affinity for the dispersion medium (solvent) and exhibit weak interactions between the dispersed phase and the dispersion medium.

2. **Characteristics of Lyophilic Sols**:
- In contrast, lyophilic sols are "solvent-loving" and have a strong affinity for the dispersion medium. They are easier to form and are typically associated with organic compounds.

3. **Identifying the Nature of the Given Options**:
- To identify which sol is lyophobic, we need to analyze the nature of the options provided. Generally, inorganic substances tend to form lyophobic sols, while organic substances form lyophilic sols.

4. **Examples of Lyophilic and Lyophobic Sols**:
- **Lyophilic Sols**: Gelatin, starch, gum arabic, egg albumin, proteins (organic compounds).
- **Lyophobic Sols**: Sulphur, arsenic trisulfide (As2S3), gold sol, ferric hydroxide (inorganic compounds).

5. **Conclusion**:
- Among the options, sulphur is an inorganic compound and thus is classified as a lyophobic sol. The other options (gelatin, starch, gum arabic) are organic and hence are lyophilic.

### Final Answer:
The correct answer is **sulphur**, as it is the lyophobic sol among the given options.

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