PHENOL. 295 



mic acid) C 6 H 2 (N0 2 ) 2 (NH 2 )OH. The ammonium salt is 

 produced by conducting sulphuretted hydrogen into 

 an alcoholic solution of ammonium picrate ; by decom 

 posing this with acetic acid the free acid is obtained. 

 Red needles ; fusing point, 165 ; slightly soluble in 

 water, more readily in alcohol and mineral acids. 

 Diamidonitrophenol C 6 H 2 (N0 2 )(N&quot;II 2 ) 2 .OH. Is obtained, 

 like the preceding compound, when aqueous solutions 

 are employed. Dark yellow needles or narrow laminae. 

 Yields salts both with bases and acids. 



Sulphophenolic acid, C 6 II 4 j g Q 2 Q^ Phenol 



dissolves readily in concentrated sulphuric acid, two 

 isomeric acids, parasulphophenolic and metasulphophe- 

 nolic acids, being formed. At the ordinary temperature 

 the meta-acid is formed almost exclusively, but with 

 the aid of heat this is readily converted into the para- 

 acid. The acids can be best separated by the prepara 

 tion and partial crystallization of their potassium salts. 

 Potassium parasulphophenolate crystallizes first in 

 long, hexagonal plates that contain no water. From 

 the mother-liquor, potassium metasulphophenolate is 

 deposited in long, colorless, spicular crystals that con 

 tain two molecules of water of crystallization. The 

 other salts of parasulphophenolic acid are also, as a 

 rule, more difficultly soluble in water than those of 

 metasulphophenolic acid. The para-acid is also ob 

 tained by decomposing diazobenzenesulphuric acid. 

 The free acids are not known in a free state. 



Disulphophenolic acid, C 6 H 3 j , g Q 2 Q^^ Is 



formed by heating phenol or the sulphophenolic acids 

 with an excess of concentrated sulphuric acid ; and by 

 the action of concentrated sulphuric acid on diazoben- 

 zene sulphate (p. 266). The acid, separated from the 

 barium or lead salt, crystallizes in very deliquescent, 

 concentrically-arranged needles of a silken lustre. The 

 solutions of the free acids, as well as those of its salts, 

 are colored ruby-red on the addition of iron chloride. 



