NAPHTALINE. 



mately, in the opinion of M. Reichenbach, as a coloiu 

 in dyeing. 



Besides the bodies described, other substances ha\ 

 found among the products of the distillation of woov 

 which the names cedriret, chrysene, pyrene and capnomor \\ , e 

 been given. 



PRODUCTS OF THE DISTILLATION OF COAL. 



The general products of the distillation of coal, which appear 

 in gas-making, are : 1, the residuary carbon or coke; 2, gaseous 

 compounds of carbon and hydrogen, including olefiant gas 

 (page 422) ; 3, a watery liquid, containing salts of ammonia ; 

 and, 4, tar. 



When the tar is distilled with water, an oily liquid comes 

 over, and there remains behind a black resinous substance, or 

 pitch, of the nature of which little is known. The oil is a mix- 

 ture of several bodies, some of which are capable of combining 

 with bases, and some with acids. Particular substances have been 

 isolated, to which the names, leucol, pyrrol, cyanol, carbolic acid, 

 rosolic and brunolic acids are applied, but the most remarkable 

 product in coal-tar is naphtaline, which is sometimes found 

 sublimed pure, in white crystalline plates, in the gas apparatus. 



NAPHTALINE. 



Formula : C 20 H 8 . M. Laurent has observed that this sub- 

 stance is best obtained from tar which is somewhat old. The 

 tar is boiled in air till it is deprived of water, and then dis- 

 tilled in a retort with a copper adopter or connecting tube, and 

 glass receiver. The first portion of oil distilled is of a yellowish 

 colour, which becomes dark coloured in air, and allows much 

 naphtaline to fall when cooled to 14 or 10 Fahr. If re-dis- 

 tilled, and the last portions received apart, they yield naphtaline 

 in large quantity when cooled. To purify naphtaline, it is crys- 

 tallized twice from alcohol, taking care to press the crystals 

 each time in folds of cotton cloth. If the oil is submitted for 

 some time to a current of chlorine, it yields afterwards an 

 increased product of naphtaline. 



