PHENOL. 295 



mic acid) C 6 H 2 (N0 2 ) 2 (OTI 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 K 2 (^"0 2 )(]SriI 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. 



{OTT 

 SO 2 OH Phenol 



dissolves readily in concentrated sulphuric acid, two 

 isomeric acids, parasufyhophenolic 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 , 2 V, 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. 



