Butter of tin is

Options

A. `SnCl_(2)*5H_(2)O`
B. `SnCl_(2)`
C. `SnCl_(4)`
D. `SnCl_(4)*5H_(2)O`

Answer

To determine what "butter of tin" is, we need to analyze the options given and understand the chemistry behind tin compounds.

### Step-by-Step Solution:

1. **Identify the Compounds**: The options provided are:
- Option 1: SnCl2.5S2O
- Option 2: SnCl2
- Option 3: SnCl4
- Option 4: SnCl4.5S2O

2. **Understand Tin (Sn)**: Tin (Sn) can form various compounds, including stannous (Sn^2+) and stannic (Sn^4+) compounds. The stannic chloride, SnCl4, is particularly important in this context.

3. **Hydrates of Stannic Chloride**: Stannic chloride (SnCl4) can form hydrates with water. The hydrates can have different numbers of water molecules associated with them, such as:
- SnCl4.2H2O
- SnCl4.3H2O
- SnCl4.5H2O
- SnCl4.6H2O
- SnCl4.8H2O

4. **Identify Butter of Tin**: The term "butter of tin" specifically refers to the pentahydrate form of stannic chloride, which is SnCl4.5H2O. This compound has a creamy texture, which is why it is referred to as "butter."

5. **Select the Correct Option**: From the options provided, the only one that corresponds to the pentahydrate of stannic chloride is:
- **Option 4: SnCl4.5S2O** (Note: The correct notation should be SnCl4.5H2O, but it seems there was a typographical error in the option).

### Conclusion:
The correct answer is **Option 4: SnCl4.5S2O**, which is known as "butter of tin."