3913. Carbonic Acid

3913.     Carbonic Acid. .An acid compound, formed by the union of carbon with oxygcn, sometimes called choke-damp. A colorless gas possessing a pungent odor and acidulous taste, rapidly absorbed by water, forming liquid carbonic acid. The agreeable pungency of ale, beer, porter, wine, etc., is in a great measure owing to the presence of carbonic acid, which they lose on exposure to the air, and then become fiat and stale. Spring and well water contain carbonic acid, and water that has been boiled has an insipid taste, from its absence. Under a pressure of 36 atmospheres at 32° Fahr. it becomes fluid, and on tho pressure being removed, congeals, from tho cold produced by its rapid evaporation. It has been estimated that the temperature falls to 180° in this experiment. Carbonic acid gas is destructive to life, and extinguishes combustion. An atmosphere containing more than its natural quantity (about 1/1000), is unfit for respiration. The air of wells, cellars, brewers' vats, etc., is frequently contaminated with this gas (choke-damp); hence tho necessity of the old plan of Jetting down a burning candle before venturing in. If the candle will not burn, man cannot breathe there. "With the bases, this acid forms carbonates.

3914. To Obtain Carbonic Acid

3914.      To Obtain Carbonic Acid. Dilute muriatic acid with 4 times its weight of water, then pour it upon fragments of marble, previously placed in a tubulated retort. Carbonic acid gas will be rapidly evolved, and may either be collected in the mercurial pneumatic trough, or applied to immediate use. "When wanted perfectly dry, it must be passed over dried chloride of calcium, or through concentrated oil of vitriol. This is tho most convenient way of procuring the gas on the small scale, or in the laboratory. Or: Dilute oil of vitriol with 3 or 4 times its weight of water, then pour it on whiting placed in a suitable vessel, and apply agitation. This is tho plan adopted on the large scale by tho soda water makers. (See No. 718 (To Charge Champagne with Gas).)

3915. Tests for Carbonic Acid

3915.    Tests for Carbonic Acid. It reddens litmus paper, extinguishes the flame of a burning taper, and forms a white precipitate in aqueous solutions of lime and baryta, which is soluble in acetic acid. By the last test, a very small quantity of this gas may be easily detected in the atmosphere of rooms, etc..

3916. Carbolic Acid

3916. Carbolic Acid, also called Phenol, Phenic acid, and hydrate of Phenyle. It consists of long, colorless prismatic crystals, which melt at about 90° Fahr. into an oily liquid resembling creosote. The crystals deliquesce in moist air, forming a sort of hydrate, which boils at 370° and has a specific gravity of 1.0G5. Heated with ammonia, it yields aniline and water; and nitric acid converts it into picric acid. Commercial creosote consists principally of hydrated carbolic acid, but is easily distinguishable from it, as carbolic acid coagulates collodion, creosote does not.

It has come into prominent notice as an efficient disinfectant.