III. NAPHTHALENE-DERIVATIVES. 



THE bodies of this group are derived from naphtha 

 lene C 10 H 8 , in the same way as the aromatic compounds 

 are derived from benzene. Naphthalene is constituted 

 very similarly to benzene ; it consists of two benzene- 

 groups, which are so united that they have two carbon 

 atoms in common : 



CH:CH.C.CH:CH 

 CH:CILC.CH:CH 



A. HYDROCARBONS, C n lI 2n - 12 - 



1. Naphthalene. 

 C 10 H 8 . 



Formation. By the dry distillation of a great many 

 organic substances at a high temperature, particularly 

 when the distillation-products are conducted through 

 a red-hot tube. It is hence contained in coal-tar and 

 wood-tar. It is also formed from alcohol, acetic acid, 

 and a number of other substances, when their vapors 

 are passed through red-hot tubes. 



Preparation. Most advantageously from coal-tar oil 

 by partial distillation and strong cooling of the distil 

 late between 180 and 220. The crude naphthalene thus 

 separated is purified by recrystallization from hot alco 

 hol, or, better, by means of sublimation. 



Properties. Large, lustrous, colorless crystalline la- 

 minse of peculiar odor and burning taste. Fuses at 

 80 ; boils at 218, and sublimes at a lower tempera 

 ture ; insoluble in water, but slightly in cold alcohol, 



