Carbolic Acid is obtained from coal tar by fractional distillation and subsequent purification, being extracted from that part of the heavy coal tar oils which distill over between 1500 and 2000 Centigrade. Specific gravity 1.065.

When pure, it is in the form of colorless acicular, interlacing crystals, which at 950 F. become an oily liquid, possessing a strong odor and taste, closely resembling creasote, having similar characters and properties, although it is a different substance. Much of what is called creasote is nothing but impure carbolic acid (Acidum Carbolicum Impuruni), combined with two other substances, similar in constitution, and known as creasole and pbosole.

Chemically considered, carbolic acid is an alcohol rather than an acid, and its crystals readily absorb moisture on exposure to the air, and are thus liquefied.

It crystallizes at 700 F., and becomes liquid at from 900 to 950 F., and fuses at 930 to 1060. It is freely soluble in alcohol, ether, chloroform, glycerine and the essential oils. When carbolic acid is liquefied and discolored by exposure, it is difficult to detect it from creasote, as it possesses the same odor, taste, caustic properties, and a like affinity for albumen. Carbolic acid is soluble in from twenty to twenty-three parts of water, the purest being the most soluble. A small quantity of water will convert it into the liquid state, but will not dissolve it. Water dissolves six per cent. of carbolic acid and five parts dissolve in one part of alcohol; four in one part of ether; three in one part of chloroform; seven in two parts of glycerine, and four in seven parts of olive oil. It is also soluble in carbon disulphide, benzol and fixed and volatile oils. The best quality of carbolic acid contains two per cent. of water and should be hard and dry, with no odor of creasote nor of volatile sulphur compounds. Crystallized carbolic acid may be dissolved by a small quantity of cologne water; and to prevent recrystallization and prepare it for use (in the form of injections, for example), the bottle containing it should be warmed by immersion in hot water, until it becomes fluid, and about five per cent. of rectified alcohol, or a few drops of glycerine, be added.

The red color which it assumes on exposure is thought to be caused by the ammonia in the air, and also by the presence of copper in the acid, which is affected by the ammonia of the atmosphere.

Medicinal Properties And Action

Carbolic acid resembles creasote so closely in many of its characters and medicinal properties, that the therapeutic applications are the same in the case of both of these substances. Many, however, consider carbolic acid to be more efficacious in obstinate discharges than creasote; and also less irritating in its crystalline form when applied to very sensitive organs, such as the pulp of a tooth.

In its pure state it is escharotic; when diluted, it is rubefacient, anaesthetic and antiseptic. Internally administered, it is sedative and carminative, possessing the power of allaying vomiting and gastric irritability.

Its powers as an antiseptic and germicide are not now considered to be equal to those of some other substances, such as bichloride of mercury, iodine, aristol, etc., although it is yet regarded as a useful and important agent. It is irritant to the skin and other tissues, and capable of being absorbed to a dangerous amount. Eisentein regards carbolic acid as an antipyretic as inferior to salicylic acid, and others regard boric acid as possessing equal antiseptic properties. As a local anaesthetic, carbolic acid exerts a very soothing influence upon painful tissues ; hence it is beneficial in odontalgia, and for pulp dressing. On account of its solubility, a variety of solutions of special value can be formed with it, which are especially serviceable as antiseptic applications.

The application of large quantities of carbolic acid to an extensive surface is, however, dangerous, as cases of fatal poisoning have resulted by the absorption of this acid; hence, care is necessary in its use as an external application.

Its nauseous odor and taste and its caustic action render it objectionable, unless greatly diluted, for internal administration. To obviate such objections, it is recommended to use it in the form of sulpho-carbolates.

When applied to the skin or to mucous membrane, it produces a burning sensation, of short duration, and the eschar is at first whitish, afterward becoming brown or black, and surrounded by a zone of inflammatory redness; and, notwithstanding its power to coagulate albumen, is rapidly diffused into the blood. Carbolic acid exists in the blood as a carbolate; and the blood itself does not appear to undergo any change in its corpuscular elements. It is in part consumed in the body, and the products of its combustion are excreted in the urine. Solutions of carbolic acid of adequate strength will check suppuration, and correct the fetor of ulcers, and has a beneficial effect on bone as well as on the soft tissues in necrosis, etc.

Therapeutic Uses

Internally, it is employed for nausea and vomiting due to an irritable state of the stomach, in scarlatina, measles and smallpox, pyrosis, etc.; as a gargle in diphtheria; as an inhalation in chronic nasal catarrh, hay asthma, whooping-cough, phthisis, etc.; as an injection in chronic cystitis, primary svphilis, erysipelas, pleuro-pneumonia and uterine diseases; as a lotion in gangrenous and other ill-conditioned ulcers, carbuncle, poisoned wounds, burns, skin diseases, scrofulous ophthalmia and itching of the skin.


Of crystallized carbolic acid, gr. 1/4 to gr. j, largely diluted. A better form, however, is one drop of the crystallized acid, liquefied by heat, in one ounce of mucilage, three times a day. The dose of glvcerite of carbolic acid (G/yceritum Acini Carbolici), made by rubbing together Dose 421 of carbolic acid with Oss of glycerine, is