An acid obtained from coal-tar oil by fractional distillation and purification.

Characters. - Colourless, acicular crystals; hygroscopic; with a tarry odour and burning taste. Becomes and remains fluid on addition of 6 per cent. of water. Solubility, 1 in 15 of water, 1 in 1 3/4 olive oil, 3 1/2 in 1 of glycerine. It does not redden blue litmus paper.

Dose. - 1 to 3 gr.

Preparations.

1. Glycerinum Acidi Carbolici

Glycerinum Acidi Carbolici. 1 to 4.

2. Suppositoria Acidi Carbolici Cum Sapone

Suppositoria Acidi Carbolici Cum Sapone. 1 gr.

in each.

Sodae Sulphocarbolas. - Sulphocarbolate of Soda. NaC5 H6SO4H1O. (Not Officinal.)

Source. - Sulphocarbolic acid is formed by direct union of Carbolic and Sulphuric Acids. The Sulphocarbolate of Soda by neutralising Sulphocarbolic acid with Carbonate of Soda.

Characters. - Whitish odourless lumps of minute colourless rhombic prisms. Soluble in water.

Dose. - 20 to 60 gr.

Action And Uses. 1. Immediate Local Action And Uses

Externally. - The principal action and uses of carbolic acid in disease depend upon its influence on fermentation and decomposition, which are intimately associated with many pathological processes. When this influence is studied apart from the body, we find that most organised ferments (fungi, bacteria, infusoria) are readily deprived of their characteristic powers by solutions of carbolic acid; whilst chemical ferments, such as pepsin and ptyalin, are much less readily affected. At the same time the products of decomposition, which are almost invariably foul-smelling, are deodorised by the phenol. The exact modus operandi in all these cases is still unknown, as are also the nature of the processes, and the relation of organisms to them. Be the explanation what it may, the power of carbolic acid, or of any substance which can thus arrest molecular processes universally at work in physiology and pathology, must be said to be enormous, both in itself and in its effects.

Carbolic acid is extensively employed in the antiseptic method of the treatment of wounds, associated with the name of its introducer, Sir Joseph Lister. A 5 per cent. solution in water serves as a spray to cleanse instruments, and to wash the skin of the part before operation. A 2 1/2 per cent. watery solution is used to purify sponges and the hands of the operator, and as a lotion. Dissolved in olive oil (1 to 10, 1 to 20, 1 to 50, or still weaker), or 1 part of carbolic acid with 7 parts of castor oil and 8 of almond oil, it is used for lubricating catheters, or as a special dressing. Carbolic acid gauze consists of unbleached cotton gauze medicated with half its weight of a mixture of carbolic acid (1), resin (4), and paraffin (4).

Coming to its physiological action proper on the human tissues, we find that carbolic acid is a local irritant to the skin, causing burning pain, anaesthesia, and finally a caustic effect with formation of a white hard eschar. It may therefore be applied to poisoned wounds and foul ulcers; and in dilute solutions is a stimulating as well as a disinfecting wash to wounds and discharging mucous surfaces or cavities, in the form of a lotion, injection, or gargle. It also relieves some forms of itching and inflammatory skin diseases, and is used with success in ringworm, where it destroys the vegetable organisms.

Apart from the body, carbolic acid is extensively used as a general disinfectant.

Internally.- In the form of vapour, carbolic acid is stimulant and disinfectant, and is used in ulceration of the throat and lungs (phthisis, dilated bronchi, gangrene, etc.), much importance having lately been attached to it in the so-called "anti-septic" treatment of phthisis, In the stomach and bowell it is a powerful irritant poison in large doses; in moderate quantity it arrests fermentative changes in the gastric contents in cases of dilatation of the viscus. Two other points may be noted in this connection; first, that carbolic acid unites with sulphates to form sulphocarbolates, which suggests the use of soluble sulphates as antidotes in poisoning by the drug; and secondly, that phenol is a natural product of the intestine or its contents.

2. Action Ox The Blood

Carbolic acid is rapidly absorbed from the unbroken skin, mucosae, wounds, subcutaneous tissues, respiratory passages, and stomach; and for a considerable time can be found in the blood unchanged. Here it steadily disappears, by conversion into compounds from which it may be again derived; uniting, for example, with sulphates, as already described. The blood is dark and slow to coagulate after poisoning by the drug.

3. Specific Action And Uses

The action of carbolic acid on the organs is of little interest to the therapeutist. It is found in them chiefly as phenol-yielding compounds; and its effects in man are chiefly those of an irritant poison. The heart first falls and then rises in frequency, from disturbance of the cardiac centre. The blood pressure rises at first, returns to the normal, and falls after a fatal dose. Dyspnoea ensues, also central in origin. Convulsions occur in the lower animals through the cord, then paralysis and collapse. The voluntary muscles are not affected by carbolic acid, but the pupil is contracted. Sensibility is not reduced by internal administration of the drug. The temperature falls slightly after medicinal doses, but may rise in cases of dangerous absorption from dressings. Carbolic acid has been given internally in fevers, it is said with good results, but is little used in this country for such a purpose. It may temporarily relieve diabetes.

4. Remote Local Action

Carbolic acid and its products rapidly leave the body, chiefly by the urine. But little of it can be recovered unchanged, for (1) part is lost in the system, being probably converted into oxalates and carbonates; (2) part appears as sulphocarbolic acid (C6H5.H.SO4) in combination; (3) part is constituted by an obscure compound; and (4) the remainder appears to give rise to a peculiar olive-green, brown, or grey discoloration of the urine, which is familiar to surgeons. It is important to note that this change in the urine bears no definite relation to the amount of carbolic acid in the blood, or the danger of poisoning. Fainting and collapse are the principal symptoms of its excessive absorption from a wound or through the skin, with or without rise of temperature. Disappearance of the sulphates from the urine, easily ascertained by ordinary tests, is a sure indication of danger. Albuminuria is sometimes induced.

Carbolic acid also leaves the body by the saliva, which is increased, and it stimulates the flow of sweat although it is not found in it.