326 BENZOIC ACID. 



cinnamic acid, cinnamic acid) by means of dilute nitric 

 acid or chromic acid ; by heating a mixture of equal 

 parts, by weight, of potassium sulphobenzolate and 

 sodium formate to fusion ; by heating benzotrichloride 

 (p. 275) with water to 150 ; by heating a mixture of 

 equal molecules of calcium phtalate and calcium hy- 

 droxide to 330-350 ; by treating hippuric acid and 

 populin with acids or bases ; by the action of acids on 

 cocain ; by the oxidation of albuminoid substances. 



Preparation. By fusing gum-benzoin. The best way 

 is to heat the gum in a shallow basin, over which is 

 placed a paper cone, made of blotting paper : the acid 

 condenses in this cone in the form of needly crystals. 

 More readily by boiling the powdered gum with cal- 

 cium hydroxide, filtering, and concentrating the result- 

 ing solution of calcium benzoate, and decomposing the 

 latter with hydrochloric acid ; the benzoic acid thus 

 separating in crystalline form. It can be purified by 

 recrystallization or sublimation. Most advantageously 

 from hippuric acid. (See Preparation of Glycocol, p. 84.) 



Properties. Lustrous, white, long, very thin, some- 

 what flexible needles and laminae. Fuses at 120, and 

 boils at 250. Difficultly soluble in cold water, easily 

 soluble in hot water and in alcohol. Easily sublimable. 

 Passes over with the vapor of water on heating its 

 aqueous solution. Its vapor and its boiling solution 

 possess a peculiar odor, that excites coughing. 



Most of its salts are soluble in water. Their solu- 

 tions give a reddish precipitate with iron chloride, con- 

 sisting of iron benzoate. 



Calcium benzoate, (C 7 H 5 2 ) 2 Ca + 3H 2 0, crystallizes 

 in lustrous, colorless, radiating prisms. Easily soluble 

 in water. 



Silver benzoate, C 7 H 5 2 .Ag, is very difficultly so- 

 luble in cold water ; crystallizes from hot water. 



Ethyl benzoate, C 7 H 5 O.O.C 2 H 5 . Colorless, viscid, 

 fragrant liquid ; specific gravity, 1.054 ; boiling point, 

 213. 



