226 RESEARCHES UPON THE CHEMICAL, PROPERTIES OF GASES. 



Mendeleeff points especially to the absence of large quantities of nitrogen com- 

 pounds in j)etroleum as an argument in favor of the hypothesis. 



, The objection has been urged against this hypothesis, that petroleum, if thus 

 produced, should be abundant in the primary rocks from which it is usually absent. 

 The originally heated condition of these rocks would have prevented the condensa- 

 tion of oil, however, and, although the vapors may have passed through the earlier 

 rocks, there is no reason to expect that condensation should have occurred before 

 reaching much higher strata. 



While on geological grounds difficult to prove or disprove, it meets with one fatal 

 objection. The composition of natui'al gas in Pennsylvania does not justify the sup- 

 position that superheated steam and carbon have been concerned in its formation. 

 We should certainly look, in such a case, to iind natural gas composed mainly of free 

 hydrogen containing small quantities of paraffins, olefines and carbon monoxide. 

 When it is considered that paraffins alone cannot under any known circumstances be 

 produced from the oxidation of carbide of iron by steam, the hypothesis does not 

 seem to be tenable. 



It is true that varying conditions of temperature might have produced a great 

 variety of hydrocarbons, but no evidence has yet been obtained that paraffins alone 

 result from such a reaction. In an experiment made with ferromanganese and dilute 

 sulphuric acid, the gas evolved was found to contain 6 per cent, of olefines,* It is 

 further to be noticed that this hypothesis requires that water should take part in the 

 process, yielding up its hydrogen, while, according to the older geological hypothesis, 

 the water may have served mainly to cover and give protection from atmospheric 

 oxidation, if it has been concerned at all in the reaction. 



Water contains dissolved oxygen, and in descending to the iron carbides, must 

 have given off' its dissolved oxygen long before reaching the region at which actual 

 formation of hydrocarbons could occur. Hence, on this hypothesis, oxygen should 

 be found in natural gas in larger quantity than the chemical tests indicate. In fact 

 in rocks of moderately high conducting power, a wide interval would exist between 

 the depth at which water boils and the much greater depth at which water vapor 

 could oxidize metallic iron in quantity. It is doubtful whether water could have 

 traversed this interval so as to reach the latter depth at all. 



Engler {Ber., Vol. XXI, p. 1816, and Yol. XXIf, p. 592) has published the 

 results of interesting investigations upon the distillation products of menhaden fish 

 oil. By conducting the distillation at a high pressure (25 atmospheres), this 

 author produced a mixture of hydrocarbon oils from which a large number of normal 



* Experiments by F. C. P. 



