Which one of the following has minimum gold number ?

Options

A. starch
B. sodium oleate
C. gum arabic
D. gelatin

Answer

To determine which of the given options has the minimum gold number, we need to understand what a gold number is and how it relates to protective colloids.

### Step-by-Step Solution:

1. **Definition of Gold Number**:
- The gold number is defined as the minimum weight of a protective colloid (in milligrams) required to prevent the coagulation of 10 ml of a standard gold sol when 1 ml of a 10% NaCl solution is added.

2. **Understanding Protective Colloids**:
- Protective colloids are substances that can stabilize colloidal solutions and prevent them from coagulating. The lower the gold number, the more effective the protective colloid is at preventing coagulation.

3. **Analyzing the Options**:
- We need to compare the gold numbers of the given options. Common protective colloids include gelatin, gum arabic, casein, and others.

4. **Identifying the Colloid with Minimum Gold Number**:
- Among the common protective colloids, gelatin is known to have the lowest gold number. This means that it requires the least amount of gelatin to prevent coagulation compared to other colloids.

5. **Conclusion**:
- Based on the understanding that gelatin has the minimum gold number, we conclude that the correct answer is **gelatin**.

### Final Answer:
The option with the minimum gold number is **gelatin**.