376 CONSIDERATION OF CARBON COMPOUNDS. 



which is first converted into ben zo- trichloride (trichlormethyl-ben- 

 zene) by passing chlorine into hot toluene : 



C 6 H 5 CH 3 -f 6C1 : C 6 H 5 CC1 3 + 3HC1. 



Benzo-trichloride, when treated with water under pressure, yields 

 benzoic and hydrochloric acids, thus : 



C 6 H 5 CC1 3 + 2H 2 : : C 6 H 5 CO 2 H + 3HC1. 



Benzoic acid forms white, lustrous scales or friable needles, having a 

 slight aromatic odor of benzoin, and an acid reaction; it is but 

 slightly soluble in cold water, but easily soluble in alcohol, ether, 

 oils, etc. 



Benzoic acid, when neutralized with an alkali, gives a flesh-colored 

 or reddish precipitate of ferric benzoate on the addition of a neutral 

 solution of ferric chloride. 



By neutralizing benzoic acid with either ammonium hydroxide, 

 sodium hydroxide, or lithium carbonate, the official salts ammonium 

 benzoate, NH 4 C 7 H 5 O 2 , sodium benzoate, NaC 7 H 5 O 2 .H 2 O, and lithium 

 benzoate, LiC 7 H 5 O 2 , are obtained. The three salts are white, soluble 

 in water, and have a slight odor of benzoin. 



Oil of bitter almond, Oleum amygdalae amarse, C 7 H 6 O or 

 C 6 H 5 COH (Benzaldehyde). As shown by the formula, oil of bitter 

 almond differs from benzoic acid in containing one atom less of 

 oxygen ; in all its reactions it behaves like a true aldehyde, being, 

 for instance, easily converted into benzoic acid by oxidation. 



It does not occur in a free state in nature, but is formed by a 

 peculiar fermentation of a glucoside, amygdalin, existing in bitter 

 almonds, in cherry-laurel, and in the kernels of peaches, cherries, 

 etc., but not in sweet almonds. The ferment causing the decomposi- 

 tion of amygdalin is a substance termed emulsine, which is found in 

 both bitter and sweet almonds. As water is required for the decom- 

 position, the emulsine does not act upon the amygdalin contained in 

 the same seed until water is added, when the decomposition takes 

 place as follows : 



C 20 H 27 NO n + 2H 2 = 2C 6 H 12 O 6 + HCN + C T H 6 O. 

 Amygdalin. Water. Glucose. Hydrocyanic Oil of bitter 



acid. almond. 



The oil is obtained by maceration of bitter almonds with water, 

 and subsequent distillation 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 aromatic 



