846 BITUMEN. 



It crystallizes by sublimation in long thin prisms, resembling 

 benzoic acid, which are inodorous, have a weak taste, fuse at 

 221, are soluble with difficulty in water, have an acid re-action 

 and form salts with bases. (Laurent.) 



Paranapht aline, C 30 H 12 ; accompanies naphtaline in tar, and 

 is deposited by the distilled oil when greatly cooled in crystal- 

 line grains. It is distinguished from naphtaline by its sparing 

 solubility in boiling alcohol. It is also less fusible and less 

 volatile, fusing at 356 and boiling above 572 (300 centig.). 

 Its best solvent is oil of turpentine. It contains carbon and 

 hydrogen in the same proportion as naphtaline, but on taking 

 the density of its vapour, it is found that 3 volumes of naph- 

 taline represent only 2 of paranaphtaline ; the density of the 

 latter is 6732. (Dumas and Laurentj Ann. de Chim. 1, 187). 



SECTION V. 



BITUMEN. 



A tarry matter, known as bitumen, is found native in various 

 parts of the world, sometimes so consistent as to be termed 

 pitch or asphalt, and often liquid and thin, as the native petro- 

 leum or naphtha of Persia and Rangoon. The latter, however, 

 always holds much fixed matter in solution. 



According to the recent observations of MM. Pelletier and 

 Walter, natural naphtha consists of several liquid and one 

 solid compound, paraffin namely, which it contains ready 

 formed. The liquid compounds are hydrocarbons, which these 

 chemists name naphtha, naphtene and naphtol. They are 

 separated from each other by distillation, as they have different 

 boiling points. 



Naphtha, C 14 H 13 ; boils between 185 and 194, is decom- 

 posed by sulphuric and nitric acid, particularly with the aid of 

 heat, less affected by chlorine; iodine dissolves in it. The 

 density of its vapour is by observation 3400, by calculation 

 3390. 



Naphthene, C 16 H 16 ; is denser than naphtha, oily, and boils 

 at 239. The density of its vapour is by observation 4000, by 

 calculation 3920. Naphtene thus forms, from its composition, 



