NAPHTHALENE. 395 



cipitate in the solutions of these salts, which is rapidly 

 converted into a purple-red, amorphous powder, oxy- 

 naphthylamine, C 10 H 9 XO. 



When nitrous acid is allowed to act on naphthy- 

 lamine, diazocompounds are formed as in the case of 

 anilin. 



Sulphonaphthalic acids, C 10 H 7 .S0 2 .OH. When 



naphthalene is carefully heated with sulphuric acid, 

 two isomeric sulphonaphthalic acids are formed, which 

 may be separated hy partial crystallization of the lead 

 or barium salts. Both salts of a-sulphonaphthalic 

 acid are much more easily soluble in water and alcohol 

 than those of the j3-acid. The a-acid, when heated, is 

 converted into the j3-acid, and hence, when naphtha 

 lene is treated with sulphuric acid at an elevated tem 

 perature (160), the product consists almost entirely of 

 j3-sulphonaphthalic acid. 



Barium a-sulphonaphthalate, (C 10 H 7 .S0 3 ) 2 Ba-h 

 H 2 0. Colorless laminae ; soluble in 87 parts water and 

 350 parts alcohol (of 85 per cent.) at 10. The lead salt, 

 (C 10 H 7 S0 3 ) 2 Pb + 3H 2 0, forms lustrous, colorless laminae; 

 soluble in 27 parts water and 11 parts alcohol at 10. 



Barium -sulphonaphthalate,(C 10 H 7 .S0 3 ) 2 Ba + IPO. 

 Colorless laminae; soluble in 290 parts water and 1950 

 parts alcohol at 10. The lead salt crystallizes in small, 

 hard scales, with varying amounts of water of crys 

 tallization ; soluble in 115 parts water and 305 parts 

 alcohol at 10. 



Naphthalene sulpho chlorides, C 10 H 7 .S0 2 C1, are 

 obtained by gently heating potassium a- and )3-sulpho- 

 naphthalate with phosphorus chloride. The ^.-chloride 

 forms lustrous laminae; easily soluble in ether; fusing 

 at 66 ; the ^-chloride is more difficultly soluble in 

 ether, and fuses at 76. 



Disulphonaphthalic acid, C 10 H 6 (S0 2 .OH) 2 ,is formed 

 by continued heating of naphthalene with an excess 



