2749.     PRING, J. N., AND FAIRLIE, D. M.  Methane Equilibrium.  Proc. Chem. Soc., vol. 27, 1911, p. 305; Jour. Chem. Soc., vol. 101, 1912, pp. 91-103; Chem. Abs., vol. 6, 1912, p. 953.

        Reaction between C and H₂ was investigated at high gaseous pressures in order to find the equilibrium values at high temperatures, and to learn the effects of pressure upon the synthesis C+2H₂=CH₄.  The high pressure greatly hastens attainment of the equilibrium value, even in the absence of a catalyst; disturbance of the equilibrium due to formation of C₂H₄ was greatly diminished by the rapid cooling caused by the water-cooled steel walls of the reaction vessel.  The experiments up to 100 atm. were carried out in a pressure furnace, while for those from 100-200 atm. a new form of furnace of smaller capacity was constructed.  With pressures between 30 and 50 atm., equilibrium was reached in about 2 hr. at 1,200°-1,300°, and in 15 min. at 1,400°, either with or without a catalyst.  At 200 atm. the reaction was still more rapid.  This indicates that finely divided C would at still higher pressures unite with H₂ with extreme rapidity, since the reaction is exothermic, thus the method might be used for preparing CH₄ on a large scale.  CH₄ is the only saturated hydrocarbon formed between 1,100° and 2,100° with pressures up to 200 atm.  In the experiments between 10 and 200 atm., the values of the ratio of the partial pressures of CH₄ and of H₂ were constant, when the same modification of C was used.  At 1,200°, 0.24% and at 1,500°, 0.07% of CH₄ is in equilibrium with H₂ and graphite.  For amorphous C the corresponding values are 0.36 and 0.21% for the metastable equilibrium.  Thus, the change of free energy of the transformation of C into graphite increases rapidly between 1,200° and 1,600°.  The mean specific heat of amorphous C thus, is higher than that of graphite between 0° and 1,200°.  The values of the equilibrium constants obtained in this work will probably give, by calculation, more accurate values of the relative specific heats of C and graphite and of C, H₂, and CH₄ at these high temperatures than could be obtained by any direct measurements.