Final answer:
Formalin is the aqueous solution of formaldehyde used as a chemical fixative and microbicide, commonly used in preservation and sterilization processes.
Step-by-step explanation:
The aqueous solution of formaldehyde gas that is used as a potent chemical fixative and microbicide is formalin. Formalin is typically a 37% to 40% aqueous solution of formaldehyde. Its effectiveness as a preservative and disinfectant comes from its property to cause the coagulation of proteins, which kills bacteria and other living organisms, and stops biological processes that lead to tissue decay. This is why formalin is widely used for preserving tissue specimens, embalming bodies, and as a sterilizing agent.