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.