44 



THE GASES IN ROCKS. 



In order to ascertain the quantitative effect of the presence of ferric 

 oxide in moderate amount, 0.77 gram of pure Fe 2 O 3 was mixed with 20.04 

 grams of diabase powder, tinting this latter a reddish brown. An analysis 

 of the resulting gas and of the original diabase gave the figures shown in 

 the following table: 



TABLE 30. 



1 Analysis No. 86. 



A comparison of these results shows that, while the yield of hydrogen 

 was diminished by the ferric oxide to less than half of what it would have 

 been, the carbon monoxide was not affected. The ferric oxide apparently 

 only went down to a state of equilibrium, and was not in sufficient quantity 

 to offset the copious evolution of hydrogen from the diabase. The brown 

 color, however, was replaced by green. 



To get rid of the iron, and particularly ferrous iron, material from the 

 same diabase specimen was treated with concentrated nitric acid for 66 

 hours. Much gas came off at first, nitric oxide, perhaps from the action 

 of the acid on pyrite, being very conspicuous. The powder, washed repeat- 

 edly on a filter until all the acid had been removed, was dried in an oven 

 overnight and then heated at 115 in an air-bath for half an hour. Two 

 and a half hours at red heat, in vacuo, then expelled only 0.23 volume of 

 gas from the diabase powder. Its composition is given in table 31. 



TABLE 31. 



A similar test was made with dilute sulphuric acid, in a vacuum. In 

 this experiment, the gas driven off by the acid during the first 2 hours 

 was collected and analyzed. Table 32 shows this to have been chiefly 

 carbon dioxide. 



