Salicylic Acid, , was originally obtained from Salicin (q.v.), but is now made on a large scale from carbolic acid, to which it is very closely allied chemically. It may also be obtained from oil of wintergreen or oil of sweet birch, which consist mainly of salicylate of methyl. It occurs in small white crystals, slightly soluble in cold water; it has no smell, but is very irritating to the nostrils, and causes sneezing; its taste is sweetish and acid. Salicylic acid is used externally as an antiseptic, and as an application in some skin diseases.
For internal use the SALICYLATE OF SODIUM is preferred, as it is much less irritating to the stomach. It occurs in small white crystals, has a sweetish taste, and is very soluble in water. It is used very largely in acute rheumatism, and controls this disease much more speedily and thoroughly than any other drug. It is of less value in chronic rheumatism. It is also employed as an antipyretic, and has been given with some advantage in gout and in diabetes. It is depressant to the heart, and if given in too large doses may induce marked disturbance of the central nervous system, characterised by buzzing in the ears, deafness, and disturbances of vision. More severe results have been noted, but they are very rare. The dose is 10 to 30 grains.