Acid colorless and have a stimulating odor, and there is corrosion, blistering after contact with human skin redness and swelling. Melting point 8.4 ℃, boiling point 100.8 ℃. Since the special structure of formic acid, and its a hydrogen atom and carboxyl group directly connected. Can also be seen as a hydroxy-formaldehyde. Therefore, both acid and formic aldehyde and nature.