Collidal dispersion have been classified into different types depending upon the physical state of the dispersed phases and the dispersion medium. They are prepared in the industry or in the laboratory by a number of methods and then purified. The protective action of lyophilic colloids was studied by Zsigmondy and he introduced a term called gold number.
Which of the following has minimum gold number?

Options

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

Explanation

To determine which of the given substances has the minimum gold number, we first need to understand what the gold number signifies. The gold number is defined as the amount of protective colloid (in milligrams) required to prevent the coagulation of 10 mL of a standard red gold sol when 1 mL of a 10% NaCl solution is added.

### Step-by-Step Solution:

1. **Understanding Gold Number**:
- The gold number indicates the protective power of a colloid. A smaller gold number means that less protective colloid is needed to prevent coagulation, indicating greater protective power.

2. **List the Gold Numbers of Each Option**:
- **Albumin**: Gold number = 0.15 mg
- **Gelatin**: Gold number = 0.005 mg
- **Starch**: Gold number = 25 mg
- **Gum Arabic**: Gold number = 0.15 mg

3. **Compare the Gold Numbers**:
- Now we compare the gold numbers of the four substances:
- Albumin: 0.15 mg
- Gelatin: 0.005 mg
- Starch: 25 mg
- Gum Arabic: 0.15 mg

4. **Identify the Minimum Gold Number**:
- Among the listed values, gelatin has the smallest gold number of 0.005 mg.

5. **Conclusion**:
- Therefore, the substance with the minimum gold number is **gelatin**.

### Final Answer:
The correct option is **gelatin** (second option).