130 Dr. M. W. Travers. The Origin of the Gases 



" The Origin of the Gases evolved on heating Mineral Substances, 

 Meteorites, &c." By MORRIS W. TRAVERS, D.Sc. Communi- 

 cated by Professor W. RAMSAY, F.R.S. Received November 

 14, Read November 24, 1898. 



The study of the gases evolved on heating mineral substances has 

 been made the subject of a number of investigations, and the results 

 have formed a basis for speculations as to the origin and history of 

 these substances. 



In a paper entitled " The Gases enclosed in Crystalline Rocks and 

 Minerals,"* Professor Tilden has suggested a theory to account for the 

 evolution of gases by mineral substances under the influence of heat. 

 He considers that the gases, which are given off on heating certain 

 rocks and minerals, are actually present in those substances in the 

 gaseous state, enclosed in small cavities under high pressure. To 

 account for their presence in these cavities he makes the suggestion, 

 " that the rock crystallised in an atmosphere rich in carbon dioxide 

 and steam, which had been, or were at the time, in contact with 

 some easily oxidisable substance, at a moderately high temperature. 

 Of the substances capable of so acting, carbon, a metal, or the pro- 

 toxide of a metal, present themselves as most probable." 



Beyond the fact that minerals give off gases when heated, there is, 

 except in the case of carbon dioxide, no direct experimental evidence 

 to show that these substances really contain the gases in the free state. 

 In many cases no cavities can be seen in thin sections of the mineral, 

 and as a mineral yields about the same quantity of gas when ground 

 to a fine powder as when it is only broken into small pieces, the cavities 

 must be assumed to be very minute if they exist at all. I do not con- 

 tend that it is impossible for a rock to contain considerable quantities 

 of gases enclosed in cavities, but I propose to prove experimentally, 

 that at least in some cases where a mineral or rock yields gases other 

 than carbon dioxide on heating, those gases are produced during igni- 

 tion, by the interaction of its non-gaseous constituents. I shall first 

 consider the formation of carbon monoxide and hydrogen from 

 minerals and rocks which contain as active constituents only water, 

 carbon dioxide, and ferrous oxide. 



A glance through the results of the analyses of some such substances, 

 and of the gases evolved by heating them, will show that the quantity 

 of hydrogen and carbon monoxide produced bears a certain relation to 

 the quantity of ferrous oxide and to the quantity of water given off on 

 heating the substance. In the following table the quantities of ferrous 

 oxide and water are expressed in terms of weight per cent. the gases 

 in cubic centimetres per gram of mineral. 



* ' Boy. Soc. Proe.,' vol. 60, p. 453. 



