Formic acid

Formic acid is the simplest carboxylic acid. Its discovery in the distillation products of ants is usually attributed to English scientist John Gray in 1671, although there is evidence that a Samuel Fisher made the discovery the year before. The name “formic” comes from formica¹, the Latin word for ant and the name of the genus to which many ants belong.

Although ants and other insects produce significant amounts of formic acid, the large worldwide production of the chemical (870 kt in 2021) is made industrially. Most of it is made from carbon monoxide, either by heating it with sodium hydroxide to produce sodium formate, which is then acidified, or via the base-catalyzed reaction of CO and methanol to make methyl formate, which is hydrolyzed to the acid. Formic acid is also a major byproduct of acetic acid manufacture.

Formic acid has a wide range of uses: in leather tanning, as a decalcifier and cleaning product, as a chemical reducing agent, as a preservative in animal feeds, and for manufacturing its salts and esters. Its synthetic method can also be reversed to liberate CO.

This is Earth Week, and this year chemists and students are celebrating it by learning about insect chemistry. Foremost among insect-produced chemicals, formic acid is produced by ants in the subfamily Formicinae (almost 300 species) and some bee species as a venom against predators and as a pheromone to warn fellow insects of danger. Ants in the Formica genus emit formic acid when they bite or spray, causing skin irritation or worse in humans. Fire ants (Solenopsis spp.) cause even more damage because their venom contains toxic alkaloids.

1. This term should not be confused with the commercial plastic laminate Formica, which was so named because it was invented as a substitute for mica in electrical insulation. Formica laminate is not made from formic acid or any of its derivatives.