Origin. - A monobasic organic acid (C6H4(OH)COOH 1: 2) existing naturally in combination in various plants [like Spiraea ulmaria (meadow-sweet), Gaultheria procumbens (wintergreen), etc.], but chiefly prepared synthetically by combining the elements of pure carbolic acid with dry carbonic acid and purifying.

Description and Properties. - Light, fine, white prismatic needles, or a light white crystalline powder, odorless, having a sweetish, afterward acrid taste; permanent in the air. It is soluble in about 308 parts of water, in 2 parts of alcohol at 25 C. (77o F.), and in 14 parts of boiling water. The addition of 2 parts of sodium sulphite or 1 part of ammonium phosphate renders it much more soluble in water.

Test. - The addition of ferric chloride to a saturated solution produces a fine bluish-violet color.

Dose. - 3-60 grains (0.25-4.0 Gm.) [7.5 grains (0.5 Gm.), U. S. P.].

Official Salts

Lithii Salicylas - Lithii Salicylatis - Lithium Salicylate (U. S. P.). - Origin. - Obtained by heating salicylic acid, lithium carbonate, and water until effervescence ceases, filtering, and evaporating. It should not contain less than 98.5 per cent. of pure lithium salicylate (C6H4(OH)COOLi).

Description and Properties. - A white or grayish-white powder, odorless, having a sweetish taste, deliquescent on exposure to air, very soluble in water and alcohol.

Dose. - 5-60 grains (0.3-4.0 Gm.) [15 grains (1 Gm.), U. S. P.].

Sodii Salicylas - Sodii Salicylatis - Sodium Salicylate (U. S. P.). - Origin. Prepared by acting on sodium carbonate with salicylic acid, straining, and heating the solution. It should contain not less than 99.5 per cent. of pure sodium salicylate (C6H4(OH)GOONa).

Description and Properties. - A white amorphous powder, odorless, sweetish, saline taste, permanent in air, soluble in 0.8 part of water, in 5.5 parts of alcohol at 25 C. (77o F.), and in glycerine.

Dose. - 5.60 grains (0.3-4.0 Gm.) [15 grains (1 Gm.), U. S. P.]. Ammonii Salicylas - Ammonii Salicylatis - Ammonium Salicylate (U. S. P.). - Definition. - It should contain not less than 98 per cent. of pure ammonium salicylate (C6H4(OH)COONH4).

Description and Properties. - It occurs in colorless, lustrous, monoclinic prisms or plates, or white crystalline powder, odorless, and having at first a slightly saline, bitter taste, with a sweetish after taste. Permanent in dry air. The concentrated aqueous solution reddens blue litmus. Very soluble in water (0.9 part), slightly less so in alcohol (2.3 parts).

Dose. - Average dose 4 grains (0.250 Gm, = 250 milligrammes), U. S. P.

Physiological Action. - Externally and Locally. - Salicylic acid is antiseptic, parasiticide, irritant to mucous membranes; possesses the power to soften the epidermis; checks perspiration when locally applied (anhydrotic).

Internally. - Digestive System. - Small doses stimulate the stomach; larger doses act as an irritant. It retards proteolysis and also hinders fermentation, and putrefaction in the gastro-enteric canal. The biliary secretion is somewhat increased, particularly as to its solids. The liver secretory cells are in some manner stimulated.

Circulatory System. - Small doses of salicylic acid have no very appreciable effect upon the circulation. Full medicinal doses first cause the heart to beat faster and stronger, increasing arterial tension; later the arterial pressure is lowered, and excessive or toxic doses cause the pulse to become slow and labored. Its tendency ultimately, even in medicinal doses, is to depress, rather than stimulate, the heart. Its effect upon the blood is to restrain the migration of the white corpuscles.

Nervous System. - In small doses it has no cerebral action. In large doses, and in some susceptible persons in full medicinal doses, salicylic acid causes cerebral congestion, indicated by a feeling of tension in the cerebrum, headache, confusion of thought, tinnitus aurium, vertigo, and sometimes delirium. Toxic doses may occasionally produce cerebral convulsions. It lessens the reflexes, but does not affect the motor peripheral nerves. Slight analgesia may be produced.

Absorption. - Salicylic acid is converted by the gastro-intestinal secretions into the sodium salicylate, in which form it enters into the circulation.

Respiratory System. - Small doses stimulate the respiratory center and the pulmonary vagi, making the respiration quicker and deeper. Toxic doses paralyze the center and vagi, causing slow and labored respiration and death from asphyxia.

Temperature. - Febrile temperature is markedly reduced by large doses of salicylic acid. The reduction takes place usually within half an hour after a dose has been taken, and lasts several hours.

Elimination. - It increases the urinary flow as a direct parenchyma stimulant. It appears in the urine as salicyluric acid.

It is a powerful diaphoretic, large doses often causing exhausting sweating. It also increases the secretion of milk and the amount of sugar in that secretion.

Elimination takes place rapidly by all the emunctories (nine minutes in the urine), but chiefly through the kidneys and skin. Traces of salicylic acid may be found for a long time after the administration of a single dose, ten to fifteen days, three days is the average. Metabolism is markedly affected, the sulphates and nitrogen in the urine going up 10 per cent. under its use. Uric acid is particularly increased. What the mechanism is is not yet determined.

Untoward Action. - Erythema, urticaria, or petechiae, accompanied by intense itching, occasionally edema of the eyelids and lower extremities, mental depression, muscular weakness, motor disturbances, sweating, and buzzing in the ears, as mentioned under Poisoning, but to a less degree. Occasionally bleeding is seen. Abortion may be induced by its use. Prolonged administration may also produce anemia.

Poisoning. - There are roaring in the ears, deafness, intense headache, vertigo, and possibly delirium, profuse and exhausting sweating, subnormal temperature, very weak, compressible pulse, feeble and shallow respirations, dimness of vision, ptosis, and often strabismus. Albumin or blood or hemoglobin may be found in the urine. The urine and feces pass involuntarily. Death usually results from respiratory failure, but is extremely rare; 15 Gm. of sodium salicylate has caused severe symptoms, but recovery has followed.