ohtained In the distillat'ion of Wood^ ^c. 1 1 



But If we compare the most brittle specimens of the pitch with 

 common specimens of asphaltum, the differences, except as far as 

 smell and taste are concerned, are not so apparent, and the reason 

 of this will be obvious on considering their fundamental similarity 

 of composition. The chief ingredients of both are carbon and 

 hydrogen. By the application of heat, the proportions of these 

 substances are altered in both cases, the hydrogen being abstracted 

 in the greatest ratio, to form the new compound (the oil) in which 

 hydrogen predominates. The ultimate result of both is charcoal. 

 Asphaltum will be found to combine pretty nearly in the same way, 

 with all the substances I have above enumerated as combining with 

 the pitch. Its essential difference however consists in its solubility 

 in naphtha, and by this test they are readily distinguished. '" 



I'he chemical difference to which these different properties of 

 substances so similar are owing, will be evident on considering some 

 of the circumstances before related. The disproportion of acetic 

 acid and carbonic oxide produced from the wood pitch, when com- 

 pared with the produce of the bitumen, proves that it contains oxy- 

 gen and azote in proportions different from those in which the same 

 substances exist in the bitumens ; and that in particular it contains 

 a considerable quantity of the former. The result would not repay 

 the toil required to investigate these proportions, which are probably 

 also subject to considerable variation. 



It is obvious that this substance is a new compound, formed by 

 the action of fire on vegetable elementary matter ; but all that we 

 can determine of its nature is, that in conformity to modern chemical 

 nomenclature, it is formed of carbon, hydrogen, oxygen, and azote. 

 The carbon and hydrogen constitute its basis, as they do that of 

 the bitumens, and the large proportion of oxygen appears to give 

 it the peculiar properties by which it is distinguished from them. 



B 2 



