438 PROCEEDINGS OF THE AMERICAN ACADEMY. 



From a number of experiments, which it is not necessary to repro- 

 duce here, it seemed that 1500° C. was about the highest temperature 

 at which equilibrium could be measured. This conclusion was based 

 on the quantity of white powder found on the walls of the furnace after 

 runs at different temperatures. Some further experiments at about 

 this temperature showed that it would be impossible to differentiate 

 between the pressure of carbon monoxide and occluded gases that 

 came out of the carbon spiral and the charge on heating in a vacuum. 

 It was therefore decided to heat the charge in some indifferent gas, 

 which could be drawn off and analyzed for the amount of carbon mo- 

 noxide present. Hydrogen was of course the only gas available. Ni- 

 trogen could not be used on account of the fact that it is absorbed by 

 calcium carbide forming calcium-cyanamide. Hydrogen would have 

 no action on carbide, 11 but it does enter into an equilibrium with 

 carbon monoxide according to the reaction 



H 2 + C^H 2 + CO 



which is the reaction of water-gas formation. If an appreciable quan- 

 tity of water were produced from hydrogen and carbon monoxide this 

 would react with the carbide and form acetylene and in analyzing for 

 carbon monoxide by absorption in cuprous chloride solution, acetylene 

 would be mistaken for the former. It can be shown, however, that the 

 quantity of water vapor formed is too small to have any effect. The 

 free energy of this reaction is given by the equation 12 



LF=- 27950 + 31.76 T+ 4.58 T log 



^H 2 



where T is the absolute temperature and the p's are partial pressures. 

 At equilibrium aF = 0, therefore placing the right-hand side of the 

 equation equal to zero, and substituting for Tits value 1773° absolute, 

 we find that for 1500° C. 



^ H '° = 0.000324. 



^CO^H, 



If PU2 equals about 90 centimeters of mercury as it does in the follow- 

 ing experiments, 



Ph.,o 



= 0.0029 

 Pco 



11 Moisson, "The Electric Furnace," p. 211. 



12 Bodlander, Zeitschr. f. Elektrochem. 1902, 8, 833. 



