Formic Acid
2 of the 6 encyclopedias on this shelf carry an entry for Formic Acid. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
an important substance in organic chemistry. It is composed of carbon, hydrogen, and oxygen in the atomic proportions of one, two, and two. It is found in a natural state in ants, caterpillars, leaves of fir, and pine trees, and in the common nettle. It occurs also in certain fruits. The acid may be obtained on a small scale by crushing the bodies of red ants and distilling the mass with water. It is obtained in commercial quantities by heating crystals of oxalic acid with glycerine and distilling the product. Pure formic acid is used in small quantities for medicinal purposes. It is a disinfectant and a preservative. It is used, also, in the manufacture of fruit essences. The acid is used largely in the dyeing and tanning trades, for which purposes it has displaced acetic acid in part. Used to dye silks, it produces a beautiful sheen. It gives mercerized cotton the rustling effect of silk.
Collier's New Encyclopedia (1921)
HCHO2, or H:CO: OH, a monobasic fatty acid, which derives its name from the circumstance that it was first obtained by distilling ants. It occurs in the animal and vegetable kingdoms, especially in the red ant, Formica rufa. When an ant walks over moistened blue litmus it turns it red. It exists also in certain caterpillars, in several secretions of the human body, as in blood, in urine, in the fish-juice, and in perspiration. It is also found in the juice of the stinging nettle, and in commercial oil of turpentine that has been exposed to the air, and in certain mineral springs.
What Has Changed in the Last Century
Chemically, both accounts still hold: formic acid is HCOOH, the simplest carboxylic acid, and it really is the ant's weapon (Formica rufa, as Collier's noted in 1921). What has gone is the manufacture. Aiton's 1910 recipe of heating oxalic acid with glycerine, and the older trick of crushing red ants and distilling them, are long obsolete; industrial formic acid now comes chiefly from carbon monoxide and methanol via methyl formate, or as a by-product of acetic acid production, in quantities of hundreds of thousands of tonnes a year. The old dyeing and tanning uses survive, but the biggest modern outlet is as a silage and animal-feed preservative, and formic acid has since been identified far beyond ants and nettles — it was detected in interstellar gas clouds by radio astronomy, and is now studied as a liquid carrier for hydrogen in fuel cells.
Written for this edition, 2026.