What Is Formic Acid?

Formic acid is a type of carboxylic acid. Its systematic name in the International Union of Pure and Applied Chemistry's chemical nomenclature is methanoic acid, but the historical name continues to be commonly used. The chemical formula for formic acid is HCOOH or HCO₂H. In its natural form, it is a colorless liquid with a strong odor.

This acid occurs naturally in the venom of stinging insects, especially ants. Some species of ants have ovipositors which have evolved into stingers that deliver a painful, irritating venom. Others are capable of squirting jets of liquid at aggressors from venom sacs which evolved to produce formic acid. The spray is can cause painful or debilitating burns to predators, and can leave humans with irritating welts. The Latin word for ant, "formica," gives its name both to the ant family, Formicidae, and to formic acid.

Renaissance naturalists were aware that anthills gave off acidic vapor, but it was not until the 17th century that research revealed the cause of this phenomenon. In 1671, an English naturalist, John Ray, collected a large number of dead ants and distilled their bodies to produce a liquid while seeking the origin of this acidic vapor. The liquid proved to be an acid, and Ray named it after the ants that had produced it. A French chemist, Joseph Gay-Lussac, was the first to synthsiez formic acid. The modern form of synthesis, based on carbon monoxide, was invented by another French chemist, Marcellin Berthelot, in 1855.

At the time of its invention, there were limited industrial applications for formic acid. Beginning in the mid-20th century, it began to be used in more and more applications, playing a major role in modern agriculture and industry, including textile and leather production. In Europe, farmers apply it to livestock feed to preserve its nutritional value and kill some kinds of bacteria. Beekeepers use products containing the compound to kill mites that can infest hives. Some cleaning products also make use of formic acid, especially cleaning products used on hard surfaces, such as limescale remover and toilet bowl cleaner.

Formic acid can be hazardous in an industrial or laboratory setting. It is corrosive and combustible, although most commercially available concentrations present little risk of combustion. It is also an eye and skin irritant, requiring laboratory workers to use eye protection and reduce exposed skin. Inhalation of fumes can cause damage to the respiratory system and optic nerves.