STATES OF THE GASES. 47 



According to these two determinations, this quartz evolved respectively 

 7.4 or 6.2 times as much hydrogen as could have been generated by the 

 reaction 3FeO + H 2 O = Fe 3 O 4 + H 2 . 



If the iron existed as pyrite, four times as much hydrogen as could 

 come from ferrous oxide might have been produced in accordance with 

 the equation 



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



On the basis of this equation the excess of hydrogen from the quartz 

 is much reduced. 



First determination: 



102.72 gms. quartz contain .............................. 0.00485 gm. Fe 



Fe (as FeS 2 ) required to give 1 c.c. hydrogen ............... 00187 gm. 



Hydrogen possible from reaction ......................... 2.60 c.c. 



Hydrogen actually obtained ............................. 4.81 c.c. 



Hydrogen not from this reaction ......................... 2.21 c.c. 



Second determination: 



102.72 gms. quartz contain .............................. 0.00580 gm. Fe 



Fe (as FeS 2 ) required to give 1 c.c. hydrogen ................ 00187 gm. 



Hydrogen possible from reaction ......................... 3.08 c.c. 



Hydrogen actually obtained ............................. 4.81 c.c. 



Hydrogen not from this reaction .......................... 1.73 c.c. 



These computations assume not only that all the iron in the quartz 

 was combined as pyrite, and that it was completely oxidized to magnetite, 

 but that the hydrogen sulphide produced was entirely dissociated into 

 hydrogen and sulphur. But the iodine titration in the gas analysis revealed 

 0.36 cubic centimeter (at and 760 millimeters) of sulphur gas whose 

 odor was that of hydrogen sulphide rather than sulphur dioxide. If this 

 were H 2 S, it would diminish the amount of hydrogen which could have come 

 from the reaction by 0.36 cubic centimeter; if, however, it were sulphur 

 dioxide the volume of possible hydrogen would be swelled by 0.72 cubic 

 centimeter in accordance with the reaction 



S + 2H 2 O = SO 2 + 2H 2 



But as there was certainly much more hydrogen sulphide than sulphur 

 dioxide absorbed by the potassium hydroxide solution, it will be safe to 

 balance the possible SO 2 formed, by the H 2 S undissociated, and ignore 

 these corrections, which would probably reduce, rather than increase, the 

 quantity of hydrogen which might result from pyrite. 



If the iron had all been locked up in the mineral chalcopyrite (CuFeS 2 ) 

 the hydrogen might be accounted for, but chemical tests failed to detect 

 the copper which this supposition would require. Just how much hydrogen 

 might be expected from iron nitride (Fe 2 N) is not certain, since, in the 

 presence of superheated steam, the nitrogen is more likely to unite with 

 hydrogen and come off as ammonia rather than as free nitrogen, and 

 ammonia is not dissociated short of the electric spark. That most of the 

 iron in the quartz is in the form of a nitride is highly improbable. Iron 

 carbide also would not yield sufficient hydrogen. 



Another mineral apparently containing very little iron, but which 

 yielded considerable hydrogen, was the beryl of analyses 101 and lOla. 



