FORMIC ACID derives its name from the circumstance of its having been first obtained from the formica rufa, or red ant. In a concentrated state, it is a fuming liquor with an irritating odor, and occasions vesication if dropped upon the skin. It crystallizes at a temperature below 3'2°, and boils at about 212', yielding a vapor which burns with a blue flame. It is a strong reducing agent, at a boiling temperature reduc ing the salts of silver, mercury, platinum, and gold..
It may be obtained in various ways, as, for example: 1. By the distillation of red ants with water (a proceeding never adopted now). 2. By the distillation of a mixture of starch, binoxide of manganese, sulphuric acid, and water; this is the usual method, and various organic matters, as sugar, chaff, bran, saw-dust, etc., may be substituted for the starch. the distillation of oxalic acid mixed with sand, or far better (accord ing to Berthelot), with glycerine; 1 equivalent of oxalic acid,(0,06,21I0) yielding 1 equivalent of formic acid -I- 2 equivalents of carbonic acid (2CO2).
Berthelot has recently obtained it synthetically by keeping carbonic oxide gas for a prolonged period in contact with hydrate of potash, at a temperature of 212°. The gas becomes gradually absorbed, and formate of potash is the result, the reaction being exhibited by the formula, 1 equivalent of hydrate of potash (KO,HO) 2 equivalents of carbonic oxide (2C0) = 1 equivalent of formate of potash (K0,021108).
Formic acid is a very common product of the oxidation of organic bodies; thus, for example, the albumivates, glycine, sugar, starch, etc., yield it in association with other products, when acted on by chromic acid; the fats aad fatty acids yield it when acted on by nitric acid; and it is a product of the action of ozone on glycerine, fats, fatty salts, acetic acid, and sugar, provided a free alkali is present. hence we can readily explain its occurrence as a product of oxidation in the animal organism, in which it not unfrequently occurs, either free or in combination. Thus we find it not only in ants, but in the poison of the bee and wasp, and in the hairs of the procession caterpil lar. It has been detected by various chemists in the sweat, in the expressed juice of the spleen, pancreas, thymus gland, and muscles, in the brain, the blood, and the urine.
The salts of formic acid, which are termed by some chemists formates, and by others formiates, require no special notice. They are all soluble, and yield a red color with persalts of iron.