FORMIC ACID. HCHO2. Syn. Hydrogen Formiate. An organic acid, obtained by oxidizing many organic substances, and found in the red ant.
Prep. Sugar, 1 part; water, 2 parts; binoxide of manganese, 3 parts; mix in a retort capable of holding fully 10 times the bulk of the ingredients, and add, cautiously, oil of vitriol, 3 parts, diluted with an equal weight of water; as soon as the first violent effervescence has subsided, heat may be applied, and the product collected and purified, as below.
Formate of lead in fine powder is introduced into a long glass tube, one end of which is connected with an apparatus evolving sulphuretted hydrogen, and the other with a
receiver. As soon as the salt is entirely decomposed (blackened) a very gentle heat is applied, and the distilled liquid collected; the product is, lastly, boiled for a minute or less, to expel any adhering sulphuretted gas. This furnishes chemically pure formic acid.
From wood spirit, 1 part; bichromate of potassium and sulphuric acid, of each 3 parts; the sulphuric acid, diluted with an equal weight of water, being gradually added last. A portion of wood spirit distils over with the acid, and may be again treated with bichromate of potassium and sulphuric acid, when a fresh portion of formic acid will be produced. This process yields a large product.
Prop., purific., &c. The products of the above processes are limpid and colourless; the stronger ones fume slightly in the air, and possess an extremely penetrating odour. The acid obtained by the second process boils at 209° Fahr., crystallises in brilliant scales below 32°, and has the sp. gr. 1·2353. Its vapour is inflammable, and burns with a blue flame. It is extremely corrosive, and rapidly destroys the texture of living organic substances. The products of the other processes are very dilute, and possess the above properties in only a minor degree. They may all be purified and concentrated by saturating them with pure carbonate of sodium or of potassium, and after subjecting the liquid to a gentle heat for a short time, and liberating the formic acid from the salt by means of dilute sulphuric acid, finally submitting the mixture to distillation, when the hydrated acid will come over perfectly pure.
Formic acid reduces the salts of mercury and silver, and forms salts with the bases termed formiates.
Formic acid is readily distinguished from acetic acid, which in many points it resembles, by heating it with a little solution of oxide of silver or mercury; the metal is reduced, and precipitated in a pulverulent state, while carbonic acid is extricated. The odours of the two acids also vary.
FORMICA. Syn. The Ant. The following are the principal species of the genus Formica. F. flava, the yellow ant. Many careful observers say this species keeps in its nest the Aphis radicans, which when its abdomen is touched by the ant, excretes a saccharine substance on which the ants feed. F. rufa, or large red ant, F. fusca; or brown ant, Polyergus rufescens, and F. sanguinea. These two latter are sometimes called amazon ants, from their pugilistic propensities. They have been known to make regular raids against other species of ants, and to carry off their larvæ and pupæ to their own nests, where they rear the insects that come of them, and afterwards employ them as slaves, causing them to excavate passages, to collect food, to carry larvæ and (so dependent do the masters become on the exertions of their bondsman) even to feed them; it being a well-attested fact that the slave holders would starve if left to themselves. See Ant.
FORMOBENZOIC ACID. (HC7H6O,CHO2). Syn. Formiate of Hydride of Benzoyle. Mandelic acid. When the distilled water of bitter almonds (containing hydrocyanic acid and the essential oil) is boiled with hydrochloric acid, a curious reaction occurs; the hydrocyanic acid is decomposed—into ammonia which unites with the hydrochloric acid, and formic acid which enters into combination with the oil of almonds—producing a new body possessed of acid properties, and termed Formobenzoic acid. On evaporating the solution the acid may be obtained in mixture with ammonia hydrochlorate, from which it may be separated by ether; the ethereal solution deposits it in rhomboidal tables. It has a sour taste and is easily soluble in alcohol. When heated it fuses at a low temperature, emitting an agreeable odour of hawthorn blossoms. (Miller.)