Which of the following is used as purgative in medicine?

Options

A. `ZnCl_(2)`
B. `HgCl_(2)`
C. `HgCl_(2)`
D. `ZnSO_(4). 7H_(2)O`

Explanation

To determine which of the given compounds is used as a purgative in medicine, we will analyze each option:

1. **ZnCl2 (Zinc Chloride)**: This compound is primarily used in industrial applications and as a disinfectant. It is not known for its use as a purgative.

2. **Hg3P2 (Mercury Phosphide)**: This compound is not used in medicine and is toxic. It does not have any purgative properties.

3. **HgCl2 (Mercuric Chloride)**: While this compound has some medicinal uses, it is primarily known for its toxicity and is not used as a purgative.

4. **ZnSO4·7H2O (Zinc Sulfate Heptahydrate)**: This compound is used in medicine but mainly as a dietary supplement and for treating zinc deficiency. It does not function as a purgative.

5. **Hg2Cl2 (Mercurous Chloride)**: This compound, also known as calomel, is historically used as a purgative. It is a white powder that is nearly insoluble in water and has been used in medicine for its laxative properties.

Based on this analysis, the correct answer is **Hg2Cl2 (Mercurous Chloride)**.

### Step-by-Step Solution:
1. **Identify the purpose of the compounds**: Understand that a purgative is a substance that helps to expel waste from the body.
2. **Evaluate each compound**: Review the medicinal uses of each compound listed in the options.
3. **Determine the correct purgative**: Identify which compound is known for its purgative properties.
4. **Conclude with the correct answer**: The compound used as a purgative is Hg2Cl2 (Mercurous Chloride).