Write two important uses of formalin.

Explanation

**Step-by-Step Solution:**

1. **Understanding Formalin**:
- Formalin is a solution of formaldehyde in water, typically containing about 37% formaldehyde by weight. It is a colorless, strong-smelling gas that is used in various applications due to its properties.

2. **First Use - Preservation of Biological Specimens**:
- One of the primary uses of formalin is in the preservation of biological specimens. It is commonly used in laboratories and medical settings to preserve tissues, organs, and biological samples. This is crucial for research, education, and medical analysis as it prevents decay and maintains the structural integrity of the specimens.

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