Phenol is made synthetically and is also obtained from coal-tar by fractional distillation. It is a crystalline substance, of faintly acid reaction, freely soluble in alcohol, glycerin, and the oils, and in 20 parts of water. The crystals, which consist of about 96 per cent. of pure phenol, melt on warming, and remain liquid on the addition of about 8 to 10 per cent. of water. The official "phenol liquefactum" is made by adding 10 parts of water to 90 parts of the crystals. This forms a stock solution which is easier to handle than the crystals regularly employed; but if water is added to it, the phenol separates as an oily liquid, and does not go into solution again until about 20 times its weight of water has been added. In other words, one can make a solution of official phenol of 5 per cent. or 90 per cent. strength, but not of any strength between. If, however, the phenol is previously dissolved in glycerin, it can be mixed in any proportion with water. Phenol precipitates albumin, gelatin, and collodion, and makes a violet color with ferric salts. Preparations. -

Phenol, 96 per cent. pure phenol in crystal form. Liquefied phenol (phenol liquefactum) - a permanent liquid made by mixing 9 parts of phenol crystals with 1 of water. Ointment, 3 per cent. in white petrolatum. Phenol tends to separate out on long standing. Glycerite, a 20 per cent. solution in glycerin. Dobell's solution (liquor sodii boratis compositus, N. F.), which contains 0.3 per cent. of phenol and 1.5 per cent. each of sodium bicarbonate and borax, with glycerin and water. Pharmacologic Action. - Microorganisms. - Phenol exerts a powerful precipitating effect upon protoplasm. This precipitate is not due to chemic combination, but to change of solvent, i. e., the protoplasmic elements are insoluble in a solution of phenol. There is no chemic action, and the phenol can be washed out of the tissues by a solvent. Since it is not chemically combined, it has greater penetrating power than most of the disinfectants. Even very dilute solutions, 1: 500, cause the prompt cessation of motion of protozoa, leukocytes, spermatozoa, and ciliated epithelium, the protoplasm of the cell becoming granular and the cell soon disintegrating.

Bacteria, as they have a cell wall, are more resistant; yet even these are penetrated more readily by phenol than by most germicides. The susceptibility to the phenol varies greatly with the different kinds of bacteria, and the spores are so resistant that they require to be exposed to strong solutions for hours. Wilbert (1916) shows that a mixture of 1 per cent. of phenol and 9 per cent. of alcohol with water is distinctly more disinfectant than a 1 per cent. solution of phenol in water alone. A solution in oil has diminished antiseptic action; for the phenol has greater affinity for oil than for the water or solution of salts in the tissues, and consequently does not penetrate into the organism. A 5 per cent carbolic ointment made with lard will go rancid in spite of the antiseptic.

Very dilute solutions tend to activate both unorganized and organized ferments; stronger solutions retard their activity, and especially diminish that of the unorganized ferments of the alimentary tract.

Locally, phenol is somewhat anesthetic, tending to allay itching and pain. It is absorbed by the unbroken skin, but much more readily by mucous membranes, and it acts on the sensory nerve-endings to produce numbness, though not complete analgesia. There may also be tingling. This may occur from 1 to 5 per cent. solutions, as when the hands are kept wet with a solution in its surgical use. It thus may considerably lessen pain, but usually does not annul it. The tingling and numbness may last half an hour or more. Strong phenol produces a burn, the pain from which is sometimes not noticeable at first on account of the anesthetic action. The skin becomes white and cold from constriction of the vessels, and numb from paralysis of the ends of the sensory nerves; later it becomes red and very painful, and still later may dry up and peel off, or the superficial tissues may slough off and leave a painful, slowly healing, ulcerated area.

Both weak and strong solutions applied to a finger or toe as wet dressings have frequently resulted in gangrene, the carbolic slowly penetrating the tissues and causing their death, while the anesthetic effect prevents the warning of pain. After a few hours the finger is found to be white and dead, and it subsequently turns black on the surface. It is sometimes necessary to amputate, but usually not. Strong phenol usually causes pain early, so that measures are taken to stop the action, hence gangrene is less likely than from weak solutions.

When applied to a wound, phenol solutions coagulate the blood and protein matters and form a pellicle over the surface. This pellicle protects the germs, so that phenol may have an undesirable effect upon the body cells and no useful one on the bacteria.

On mucous membranes there are the same anesthetic and corrosive actions as on the skin. Weak solutions in the stomach are somewhat anesthetic and may allay vomiting.

Systemically, phenol resembles acetanilid in its action, but the antiseptic and collapse actions predominate, and the antipyretic action is less. At first the heart is stronger from direct stimulation of its muscle; later this is weakened. The vasoconstrictor and respiratory centers are also at first stimulated, then markedly depressed, and in fever the temperature is lowered. But collapse is readily produced, and because of this the drug is not employed for its systemic effect. We must understand these effects, however, because of the frequency of carbolic poisoning.

Fig. 63.

Fig. 63. - Carbolic-acid poisoning. Coagulation of crests of the folds of mucosa in the stomach (MacCallum).

In a study of the effects of the products of intestinal putrefaction on muscle, F. S. Lee found that in a solution of phenol, 1: 2000, a muscle did nearly twice as much work as before, while in solutions of 1: 1000 the muscle readily became fatigued and did less work (Herter).