300 CONSIDERATION OF CARBON" COMPOUNDS. 



when it distils over with hydrocyanic acid and steam, and 

 separates as a heavy oil in the distillate. 



It is an almost colorless, thin liquid of a characteristic aro- 

 matic odor, a bitter and burning taste, and a neutral reaction. 

 The pure oil is not poisonous, but the crude oil of bitter almond 

 is poisonous on account of its containing hydrocyanic acid. 



Bitter almond water, Aqua amygdalae, amarce, is made by dissolving 

 1 part of the oil in 999 parts of water. 



Salicylic acid, Acidum salicylicum, HC 7 H 5 3 or C 6 H 4 HO.C0 2 H = 

 138. Derived from benzene by introducing one hydroxyl and 

 one carboxyl residue. It is found in several species of violet, 

 and in the form of methyl salicylate in the wintergreen oil (oil 

 of Gaultheria procumbens). May be obtained by fusing potas- 

 sium hydrate with salicine, a glucoside found in the bark ot 

 willow. 



Salicylic acid is manufactured from carbolic acid by passing 

 carbon dioxide through sodium acid carbolate (sodium phe- 

 noxide), when sodium salicylate remains and carbolic acid distils 

 over: 



H 0. 



C 6 H 5 HO. 



Carbolic 

 carbolate. dioxide. acid. 



Sodium salicylate, thus obtained, is decomposed by hydro- 

 chloric acid : 



C 6 H 4 ISraOCO 2 Na 4- 2HC1 = C 6 H 4 HOCO 2 H 4- 2NaCl. 



Sodium salicylate. Hydrochloric Salicylic acid Sodium 



acid chloride. 



Salicylic acid is a white, solid substance, odorless, or ot a 

 slight aromatic odor, having a sweetish, slightly acrid taste, and 

 an acid reaction ; it is but sparingly soluble in cold water, but 

 readily, soluble in alcohol, ether, etc.; it fuses at about 175, and 

 sublimes at 200; it is a valuable disinfectant and antiseptic. 



Salicylic acid assumes a fine violet color with ferric chloride. 



By dissolving the alkaline hydrates in salicylic acid, the 

 various salts may be obtained, as, for instance, sodium salicylate,^ 



