Question

Formalin is an aqueous solution of:

Hint:

Formalin is about 37–40% formaldehyde in water and is widely used as a preservative in biological specimens.

Answer 1

Step 1: Understanding Formalin.
Formalin is a common laboratory chemical that is used as a disinfectant and preservative. It is specifically an aqueous solution of formaldehyde gas in water.

Step 2: Composition of Formalin.
Formalin typically contains about 37–40% formaldehyde dissolved in water, along with a small amount of methanol to prevent polymerization.

Step 3: Analyzing the options.
- (A) Fluorescein: This is a dye, not related to formalin.
- (B) Formaldehyde: Correct. Formalin is an aqueous solution of formaldehyde.
- (C) Formic acid: This is a different organic acid, not formalin.
- (D) Acetic acid: This is vinegar’s main component, not related to formalin.

Step 4: Conclusion.
Hence, the correct answer is that formalin is an aqueous solution of formaldehyde.

Final Answer: \[ \boxed{\text{(B) Formaldehyde}} \]