Formic acid was first collected by distilling large numbers of ants
In 1671 the English naturalist John Ray described how he obtained a sharp-smelling acid by distilling a great many ants. The substance took its name from formica, Latin for ant. It is the simplest carboxylic acid, and it also lurks in stinging nettles, onions and the air above forests.
Alchemists had noticed as early as the 15th century that anthills gave off an acidic vapour. Ants use the acid to attack and defend, and wood ants of the genus Formica can spray it at prey or intruders. The puss moth caterpillar does the same when threatened, stingless bees of one genus carry it, and the tiny hairs of stinging nettles hold it too. Much of the formic acid in the atmosphere comes from forests.
Plenty of everyday food contains traces. Onions are rich in it by comparison, with about 45 milligrams per 100 grams, while apples hold about 2 and cucumbers barely a tenth of a milligram. Chemically it is a colourless, pungent liquid, roughly ten times stronger an acid than acetic acid, the sour part of vinegar. Its molecules cling to one another through hydrogen bonds, so even as a gas it travels in pairs and does not obey the ideal gas law.
Joseph Gay-Lussac first made it synthetically, and in 1855 Marcellin Berthelot devised a route from carbon monoxide resembling the modern one. For a long time it was a minor industrial chemical, until the late 1960s, when acetic acid manufacture began producing it in large quantities as a side product. Today plants combine methanol and carbon monoxide to make methyl formate, then split it with water. In 2009 world capacity reached 720 thousand tonnes a year, split roughly evenly between Europe, mainly Germany, and Asia, mainly China.
Its biggest use is in livestock feed, where it acts as a preservative and antibacterial that slows spoilage and helps feed keep its nutritional value. Chemists also value it as a handy source of hydrogen: over certain metal catalysts it breaks down into hydrogen and carbon dioxide.
Source: Formic acid
