338 TOLUIC ACIDS. 



Nitrohippuric acid, C 9 H 8 (]TO 2 )N0 3 ,is formed, when 

 hippuric acid is added to a mixture of equal volumes of 

 concentrated sulphuric and nitric acids ; and separates 

 on the addition of water, and partial neutralization of 

 the acid with sodium carbonate. Fine, white prisms 

 of a silky lustre ; fuses between 150 and 160 ; diffi- 

 cultly soluble in cold water, easily soluble in hot water 

 and in alcohol. Boiled with hydrochloric acid, it is 

 resolved into glycocol and nitrobenzoic acid ; ammo- 

 nium hydrosulphide reduces it to amidohippuric acid, 

 C 9 H 8 (^"H 2 )(N0 3 ), which crystallizes in small, white 

 laminae, difficultly soluble in water. 



2. Acids, C 8 H 8 2 . 

 a. Toluic Acids. 



CO.OH. 



1. Ortho-toluic acid. Is obtained by oxidation of 

 ortho-xylene with dilute nitric acid, and is purified in 

 the same way as para-toluic acid (see below). Also by 

 distilling potassium ortho-sulphotoluenate with potas- 

 sium cyanide, and treating the cyanide thus formed 

 with alcoholic potassa. Long, very fine needles ; fus- 

 ing point, 102 ; difficultly soluble in cold water, easily 

 in hot water. When warmed with chromic acid 

 (potassium bichromate and dilute sulphuric acid), it is 

 burned completely, yielding carbonic anhydride and 

 water. 



Calcium ortho-toluate, (C 8 H 7 2 ) 2 Ca + 2II 2 0, crys- 

 tallizes in easily soluble needles. 



2. Meta-toluic acid (Isotoluic acid). Is produced 

 together with para-toluic acid by oxidation of the 

 xylenes (p. 283) contained in coal-tar ; it cannot, how- 

 ever, be separated from the para-acid. It is obtained 

 in a pure condition by the action of sodium-amalgam 

 on a solution of brommeta-toluic acid. Colorless nee- 



