evolved on heating Mineral Substances, Meteorites, c(V. 131 



Mineral. Locality. FeO. H 2 O. H 2 . CO. CO 2 . 



Chlorite ......... Zoptan, Moravia 10*6 4*6 2-180 0*494 0-123 



Serpentine 1 ... Zermatt ......... 2*7 9*5 0*800 none none 



Gabbro ......... Isle of Skye ...... 6*1 1-5 0*490 none none 



Mica ............ Westchester, 1-4 0'13 ~~(H)8 0'150 



Pennsylvania 



Foliated talc 2 ... Greiner, Tyrol ... 0'4 4'5 0*04 0*070 



Felspar 3 ......... Peterhead ......... 2*1 1*00 0*214 1*201 



1 Analysis by Miss E. Aston, Q.uart. Jour. Greol. Soc.,' 1896, vol. 52, p. 456. 



2 The talc lost only 0'06 per cent, of water when heated in the hard glass tube, 

 ren.ainder came off at a very bright red heat. 



3 The felspar contained free iron. 



The estimation of the ferrous iron was conducted in the following 

 manner. The sulphuric acid (30 per cent.), previously boiled and 

 cooled in a corked flask, was poured into the bottom of a thick-walled 

 glass tube. The mineral was weighed out into a small test-tube with 

 a glass rod sealed to the bottom of it to support it above the sulphuric 

 acid in the large tube during exhaustion. The tube was drawn out at 

 the end as in fig. 1, attached to a Topler pump by a rubber tube, 

 exhausted, and sealed at the capillary. After heating to 170 till the 

 mineral was entirely decomposed the tube was again attached to the 

 pump as in fig. 2, the point of the capillary was broken inside the rubber 

 tube and the gas contained in it was pumped out and analysed. The 

 tube was afterwards cut open and the ferrous sulphate was estimated by 

 titration with a solution of potassium permanganate. In the case of the 

 mica it was necessary to use strong sulphuric acid to decompose the 

 mineral. 



In general, the gas contained in the sealed tube consisted only of 

 carbon dioxide. In the case of the felspar from Peterhead granite, and 

 of certain helium-yielding minerals, the gas also contained hydrogen. 

 I shall deal with these minerals separately. 



That the minerals, which on heating give hydrogen and carbon mon- 

 oxide, give neither of these gases when decomposed by means of dilute 

 sulphuric acid, is almost sufficient evidence to show that the gases are 

 not present in the minerals in a free state, either occliided, or enclosed in 

 cavities. That the amount of hydrogen and carbon monoxide pro- 

 duced by heating a mineral is, as I have shown, proportional to the 

 amount of ferrous oxide, water, and carbon dioxide present in it, may 

 be taken as evidence that the gases are produced by the interaction of 

 these substances when the mineral is heated, according to the equa- 

 tions : 



2FeO + CO, = FeO+CO 



