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:CH.C.CH:CH 



A. HYDROCARBONS, C w H 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, 



