'374 PBINCIPLES OF CHEMISTRY 



districts as, for instance, by the slopes of the Caucasian chain, on 

 inclines lying in a direction parallel to the range T-an oily liquid issued 

 from the earth together with salt water and hot gases (methane and 

 others) ; it has a tarry smell and dark brown colour, and is lighter than 

 water. This liquid is called naphtha or rock oil (petroleum) and is 

 obtained in large quantities by sinking wells and deep bore-holes in 

 those places where traces of naphtha are observed, the naphtha being 

 sometimes thrown up from the wells in fountains of considerable 

 height. 52 The evolution of naphtha is always accompanied by salt 

 water and marsh gas. Naphtha has from ancient times been worked 

 in Russia in the Apsheron peninsula near Baku, and is also now 

 worked in Burmah (India), in Galicia near the Carpathians, and in 

 America, especially in Pennsylvania and Canada, &c. Naphtha does 

 not consist of one definite hydrocarbon, but of a mixture of several, 

 and its density, external appearance, and other qualities vary with the 

 amount of the different hydrocarbons of which it is composed. The 

 light kinds of naphtha have a specific gravity about O8 and the heavy 

 kinds up to 0-98. The former are very mobile liquids, and more vola- 

 tile ; the latter contain less of the volatile hydrocarbons and are less 

 mobile. When the light kinds of naphtha are distilled, the boiling 

 point taken in the vapours constantly changes, beginning at and 

 going up to above 350. That which passes over first is a very mobile, 

 colourless ethereal liquid (forming gazolene, ligroin, benzoline, &c.), 

 from which .the hydrocarbons whose boiling points start from rnay ; 

 be extracted namely, the hydrocarbons C 4 H }0 , C 5 H 12 (which boils 

 at 30), C 6 H U (boils at 62), C 7 H 16 (boils about 90), &c. Those 

 fractions of the naphtha distillate which boil above 130, and contain 

 hydrocarbons with C 9 , C 10 , Cj,, &c., enter into the composition of the 



refining by repeated fractional distillation, which can be very conveniently done by 

 means of steam rectification that is, by passing the steam through the dense 

 mass), depends not only on the predominance of saturated hydrocarbons in the 

 former, and naphthenes, C,,H 2)i , in the latter, but also on the diversity of composition and 

 structure of the corresponding portions of the distillation. The products of the Baku 

 naphtha are richer in carbon (therefore in a suitably constructed lamp they ought to give 

 a brighter light), they are of greater specific gravity, and have greater internal friction 

 (and are therefore more suitable for lubricating machinery) than the American products 

 collected at the same temperature. 



52 The formation of naphtha fountains (which burst forth after the higher clay strata 

 covering the layers of sands impregnated with naphtha have been bored through) is with- 

 out doubt caused by the pressure or tension of the coriibustible hydrocarbon gases 

 which accompany the naphtha, and are soluble in it under pressure. Sometimes these 

 naphtha fountains reach a height of 100 metres for instance, the fountain of 1887 near 

 Baku. Naphtha fountains generally act periodically and their force diminishes with the 

 lapse of time, which might be expected, because the gases which cause the fountains find 

 an outlet, as the naphtha issuing from the bore-hole carries away the sand which was 

 partially choking it up. 



