10 



THE GASES IN ROCKS. 



ide might then be produced by the reducing action of metallic iron or fer- 

 rous oxide upon steam and carbon dioxide at high temperature, according 

 to the reactions 



3Fe + 4H 2 = Fe 3 O 4 + 4H 2 



3Fe -I- 4CO 2 = Fe 3 O 4 + 4CO 



The origin of the marsh-gas is assigned in this paper to the action of 

 water at high temperature upon metallic carbides, or similar compounds, 

 in the earth's interior, as suggested by Mendeleef 1 and the more recent 

 studies of Moissan. 2 



A year after the publication of Tilden's article, criticism of his paper, 

 and in fact of the work of all previous investigators in this line, was made 

 by M. W. Travers, who undertook to prove that the different gases, not 

 excluding even argon and helium, did not exist in the gaseous state in min- 

 erals, but were formed by chemical interaction between the non-gaseous 

 materials in the combustion-tube. 3 The key to his position lay in the two 

 reversible reactions 



3FeO + H 2 = Fe 3 4 + H 2 



3FeO + CO 2 = Fe 3 4 + CO 



His table revealed a certain relation between the hydrogen and carbon 

 monoxide produced, and the quantity of ferrous oxide and water present 

 in the mineral. It is shown in table 6. The figures for FeO and H 2 refer 

 to the percentages in the rock; the gases are expressed in cubic centimeters 

 per gram of rock. 



TABLE 6. 



Four of these (including the mica of meta-sedimentary origin) were 

 secondary minerals whose gas may have been produced entirely by chem- 

 ical reactions in the tube, without having very great bearing upon the 

 problem of the gas-content of primary minerals and rocks which have not 

 undergone extensive weathering and alteration. The only rock tried, the 

 gabbro, may be pointed out as unique in yielding only hydrogen without 

 either of the oxides of carbon or nitrogen. 



Armand Gautier, 4 in 1901, came to the conclusion that the gases which 

 he obtained from several igneous rocks did not escape from inclusions, for 

 the most part, but were products of chemical reactions at raised tempera- 

 tures. A small quantity of gas was obtained by heating granite powder, 

 moistened with pure water, up to 300 in a vacuum. By heating the same 



1 Mendele'ef, Prin. of Chem., transl. of Kamensky and Greenaway, vol. 1, pp. 364-365. 

 2 H. Moissan, Proc. Roy. Soc., vol. 60 (1896), pp. 156-160. 

 3 M. W. Travers, Proc. Roy. Soc., vol. 64 (1898), pp. 130-142. 

 *A. Gautier, Comptes Rendus, vol. 132, pp. 58-64, 189-194. 



