BENZENE SERIES. AROMATIC COMPOUNDS. 377 



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 O 3 or C 6 H 4 OH.CO 2 H 

 = 138. Derived from benzene by introducing one hydroxyl and 

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

 the form of methyl salicylate in the wintergreen oil (oil of Gaul- 

 theria procumbens). May be obtained by fusing potassium hydroxide 

 with salicin. 



Salicylic acid is manufactured from carbolic acid by passing carbon dioxide 

 through sodium carbolate (sodium phenoxide), when sodium salicylate remains 

 and carbolic acid distils over : 



C 6 H 5 OH + NaOH = C 6 H 5 ONa 4- H 2 O. 

 Carbolic acid. Sodium Sodium 



hydroxide. carbolate. 



2(C 6 H 5 ONa) + C0 2 = C 6 H 4 NaOCO 2 Na + C 6 H 5 OH. 



Sodium Carbon Sodium salicylate. Carbolic 



carbolate. dioxide. acid. 



Sodium salicylate, thus obtained, is decomposed by hydrochloric acid : 



a + 2HC1 : C 6 H 4 OHCO 2 H + Nad 

 Sodium salicylate. Hydrochloric Salicylic acid. Sodium 



acid. chloride. 



Salicylic acid is a white, solid, odorless substance, 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 157 C. (315 F.), and sublimes at 200 C. (392 F.). 

 It is a valuable antiseptic. 



By dissolving the alkali hydroxides in salicylic acid, the various 

 salts may be obtained, as, for instance, sodium salicylate, NaC 7 H 5 O 3 , 

 and lithium salicylate, LiC 7 H 5 O 3 , both of which are white, soluble 

 salts. 



Analytical reactions. 



1. Add to solution of salicylic acid or its salts ferric chloride : a 

 reddish-violet color is produced, yet noticeable in solutions containing 

 1 part of salicylic acid in 500,000 parts of water. (Plate VI.,'2.) 



2. Add some cupric sulphate : a bright-green color will result. 



3. Dissolve some salicylic acid or sodium salicylate in methyl 

 alcohol and add one-fourth the volume of sulphuric acid. Heat 



