254 Notes on Petroleum 



gen tlian the Albert coal analysed by Wetlierell ; while the 

 idrialine or bitumen found with the mercury ores of Idria, ap- 

 proaches very nearly in composition to the bituminous coals 11, 

 12 and 13, with which many asphalts maybe said to be isomeric. 

 It is bowever probable that those oxygenized bitumens, unlike the 

 coals, are products of the oxydation of naphtha or petroleum, by 

 a process similar to that by which resins are derived from vege- 

 table hydrocarbons. These formulas must be taken as repre- 

 senting not the true equivalents, but only the proportions of 

 the elements in the bodies in question, which are in most 

 cases mixtures of various substance. This is especially true of 

 naphtha, which may be taken as the representative of pure unoxy- 

 dised petroleum, and which is separated by distillation into oils 

 of very different boiling points. The late analyses by TJelsmann 

 of the rectified rock oil from Sehnde near Hanover, gave the for- 

 mula Ci 8H20, and according to De la Rue and Miiller the 

 greater part of the Rangoon petroleum consists of hydrocarbons 

 in which the number of equivalents of hydrogen is a little greater 

 than the carbon ; one gave C2 6H2 s. Associated with these are 

 however portions of bodies containing a less proportion of hydro- 

 gen, so that we may conceive the mean composition of petroleum 

 to be represented, as in the preceding table, by equal equivalents 

 of hydrogen and carbon ; many forms of solid bitumen also, as 

 ozokerite and hatchetine, have the same general composition. 



By referring to what has been said above it will be seen that 

 the final result of the third process of decomposition of woody 

 fibre, in which the air being excluded, the oxygen is shared be- 

 tween the carbon and hydrogen, would be CaoHs. A similar 

 result would be obtained, with the simultaneous evolution of 

 marsh gas, if we suppose 6 CO2 + 8 HO + 3 CH2 to be removed 

 from an equivalent of woody fibre, leaving CisHe ==€2 oHs = 

 C24H9.S, which approaches the composition of most bituminous 

 coals and of idrialine. A farther elimination of marsh gas would 

 leave a residue of pure carbon, and thus, as Bischof has sug- 

 gested, vegetable matters may be converted into anthracite with- 

 out the intervention of a high temperature. 



The elimination of the whole of the oxygen in the form of car- 

 bonic acid would leave a compound with a large excess of 

 hydrogen, of which it would be necessary to remove a portion 

 in the form of water or marsh gas in order to reduce the residue 

 to the composition of petroleum. We know of no combination 



