580 CONSIDERATION OF CARBON COMPOUNDS. 



ether, oils, etc. Shaken in solution with hydrogen dioxide, benzoic 

 acid is converted into salicylic acid. 



Benzoic acid, prepared by sublimation from gum benzoin, has a 

 slight aromatic odor resembling that of benzoin ; the acid obtained 

 synthetically is odorless. 



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. 



Benzoic acid and its derivatives, taken internally, are eliminated in the 

 urine as hippuric acid, C 6 H 5 CO.NH.CH 2 COOH (benzoyl-amino-acetic acid), 

 and its derivatives. 



Many halogen, nitro- and amino-benzoic acids exist which are interesting 

 in pure and technical chemistry. 



Ethyl para-amino-benzoate, C 6 H 4 (NH 2 )(COOC 2 H 5 ) (Anesthesiri), is a 

 local anesthetic, introduced as a substitute for cocaine. It is a white, odorless, 

 tasteless powder, melting at 90 to 91 C., almost insoluble in cold and diffi- 

 cultly soluble in hot water. It is soluble in 6 parts of alcohol. When placed 

 on the tongue it produces a sensation of numbness. 



Benzoyl chloride, C 6 H 5 .COC1, is obtained by distilling benzoic acid with 

 phosphorus pentachloride. It is a colorless, irritating oil, boiling at 200 C., 

 slowly decomposed by cold water, but more stable than acetyl chloride. It 

 acts on hydroxyl compounds, forming benzoic acid esters, thus : 



C 6 H 5 .COC1 + C 6 H 5 OH C 6 H 5 COOC 6 H 5 + HC1. 



Phenyl benzoate. 



This process of introducing the benzoyl radical is known as " benzoylation." It 

 is greatly facilitated when carried out in the presence of alkali. 



Benzosulphinide, Saccharin, Benzosulphinidum, C 6 H 4 .CO.SO 2 .- 

 NH = 181.77 (Anhydro-ortho-sulphamide-benzoic acid, Benzoyl sul- 

 pJionic-imide). This substance is a derivative of benzoic acid, 

 C 6 H 5 .CO 2 H, obtained by the discoverers from toluene by the trans- 

 formations indicated in the following formulas : 



CH 3 



,CH 3 /COOH /CO, 



C.H / __> C.H/ _> C 6 H / >NH. 



-\so a jra, NSCVNH, Nao/ 



Other methods of preparing saccharin have been devised. 



