566 SALICYLIC ACID 



barks. It can also be extracted from the stems, leaves, 

 and rhizomes of violets. In these plants, and in the volatile 

 oils of the winter-green and various Spireas, it occurs as a 

 methyl salicylate. But the commercial source is sodium 

 phenol, through which carbonic acid gas is passed for several 

 hours. The mixture is raised to 482 Fahr., the residue 

 is dissolved in a limited quantity of water, and treated 

 with hydrochloric acid, when salicylic acid is precipitated, 

 and is subsequently crystallised. Commercial specimens 

 frequently contain cresotic acid. 



PROPERTIES. Salicylic acid occurs as a soft, light, colour- 

 less or faintly pink powder, consisting of minute acicular 

 crystals ; but it may be crystallised in bold four-sided 

 prisms. It is odourless, but when inhaled irritates the 

 nostrils. It has a taste at first sweet, but subsequently 

 bitter. It is soluble in 538 parts of water, 120 of olive oil, 

 200 of glycerin, 3 J of rectified spirit, 2 of ether, and 8 of lard ; 

 and its solubility is increased by admixture with sodium 

 borate or phosphate. It fuses at 311 Fahr., volatilises 

 without decomposition below 392 Fahr., but above that 

 is decomposed into phenol and carbonic acid gas. Sodium 

 salicylate, C 7 H 5 3 Na, may be obtained by the interaction 

 of salicylic acid and sodium carbonate. It occurs in small, 

 colourless scales, or in tabular crystals ; odourless, taste 

 sweetish and saline ; soluble in 10 parts water, and in 6 

 parts of rectified spirit. 



ACTIONS AND USES. Salicylic acid belongs to the benzene 

 or aromatic series of carbon compounds, and in chemical 

 constitution and physiological action is allied to benzoic 

 and carbolic acids. It is antiseptic, antiperiodic, antipyretic, 

 irritant, and astringent, and is specially useful in the 

 treatment of acute rheumatism. The acid, its alkaline 

 salts, and salicin have similar actions, but salicin is now little 

 used. 



GENERAL ACTIONS. Salicylic acid, as an antiseptic, is less 

 penetrating, but rather more powerful than carbolic acid or 

 creolin. It prevents fermentation and putrefaction. Watery 

 solutions are more active germicides than the alcoholic or 

 oily ; they have no appreciable action on the intact skin, 

 unless applied for some time ; but on a mucous membrane, 



