Formic acid, systematically named methanoic acid, is the simplest carboxylic acid. The chemical formula is HCOOH or HCO2H. It is an important intermediate in chemical synthesis and occurs naturally, most notably in some ants. The word "formic" comes from the Latin word for ant, formica, referring to its early isolation by the distillation of ant bodies. Esters, salts, and the anion derived from formic acid are called formates. Industrially formic acid is produced from methanol.
Formic acid is a colorless liquid having a pungent, penetrating odor at room temperature. It is miscible with water and most polar organic solvents, and is somewhat soluble in hydrocarbons. In hydrocarbons and in the vapor phase, it consists of hydrogen-bonded dimers rather than individual molecules. Owing to its tendency to hydrogen-bond, gaseous formic acid does not obey the ideal gas law. Solid formic acid (two polymorphs) consists of an effectively endless network of hydrogen-bonded formic acid molecules. This relatively complicated compound also forms a low-boiling azeotrope with water (22.4%) and liquid formic acid also tends to supercool.
A major use of formic acid is as a preservative and antibacterial agent in livestock feed. In Europe, it is applied on silage (including fresh hay) to promote the fermentation of lactic acid and to suppress the formation of butyric acid; it also allows fermentation to occur quickly, and at a lower temperature, reducing the loss of nutritional value. Formic acid arrests certain decay processes and causes the feed to retain its nutritive value longer, and so it is widely used to preserve winter feed for cattle. In the poultry industry, it is sometimes added to feed to kill E. coli bacteria. Use as preservative for silage and (other) animal feed constituted 30% of the global consumption in 2009. Formic acid is also significantly used in the production of leather, including tanning (23% of the global consumption in 2009), and in dyeing and finishing textiles (9% of the global consumption in 2009) because of its acidic nature. Use as a coagulant in the production of rubber consumed 6% of the global production in 2009. Formic acid is also used in place of mineral acids for various cleaning products, such as limescale remover and toilet bowl cleaner. Some formate esters are artificial flavorings or perfumes. Beekeepers use formic acid as a miticide against the tracheal mite (Acarapis woodi) and the Varroa destructor mite and Varroa jacobsoni mite. Formic acid application has been reported to be an effective treatment for warts. Formic acid is being investigated for use in fuel cells. Formic acid is often used as a component of mobile phase in reversed-phase high-performance liquid chromotagraphy (RP-HPLC) analysis and separation techniques for the separation of hydrophobic macromolecules, such as peptides, proteins and more complex structures including intact viruses. Especially when paired with mass spectrometry detection, formic acid offers several advantages over the more traditionally used phosphoric acid.