2751.     ---------------.  [PRING, J. N., AND FAIRLIE, D. M.]  Synthesis of Hydrocarbons at High Temperatures and High Pressures.  8th Internat. Cong. Appl. Chem., vol. 21, 1912, p. 65; Chem. Abs., vol. 6, 1912, p. 3363.

        Apparatus is a modified form of the pressure furnace used previously (abs. 2750).  The main reaction studied:  C+2H₂=CH₄.  Below 1,000° C and H₂ at 1 atm. react so slowly, even in the presence of Pt as catalyst, that equilibrium values are not reached within any reasonably time.  H₂ was brought into contact with a C rod heated to 1,100°-1,600° by passing an electric current through it.  The containing walls of the Ni-steel reaction vessel (750 cc.) were H₂O-cooled.  The CH₄, yielded at any given temperature of the C rod, corresponded to the equilibrium value for this temperature since CH₄ does not decompose in the colder regions of the apparatus.  Furthermore, the amount of C₂H₄ formed as a by-product at temperature below 1,500° is so slight that the reaction C₂H₄+2H₂=2CH₄, which takes place in the cooler parts does not appreciably affect results.  C₂H₂ first becomes noticeable (0.001%) at 1,650°.  Various grades of C and graphite were tried.  The Sodeau apparatus was used in analyzing the products.  Amorphous C gave higher % CH₄ than graphite.  Upon long heating of the former the values dropped owing to the gradual change into graphite.  Partly purified amorphous C heated 3 hr. at 1,275°, H₂ at 100 atm., gave equilibrium values:  21.5% CH₄, 0.25% CO, and 0.002% C₂H₄.  Pt-coated amorphous C, preliminarily purified in Cl₂, after 2.5 hr. at 1,100°, 20 atm., gave 6.35% CH₄ and 1.1% CO.  Acheson graphite, 1,200°, 2.5 hr., 105 atm., 17.5% CH₄ and no CO.  Other graphites, 1.6-4.7% CH₄.  At 1,200°-1,300° and at 30-50 atm., equilibrium is reached in about 2 hr.; above 1,400°, in about 15 min.  The reaction velocity at 200 atm. exceeds by far that at 1 atm.  The results are in agreement with the mass action law.  At 1 atm. the equilibrium value of CH₄, in presence of graphite, is 0.25% at 1,200° and 0.07% at 1,500°.  With amorphous metastable C the values are 0.36% at 1,200° and 0.18% at 1,500°.  At n atm., the CH₄ pressure is n times that at 1 atm.  From the data obtained, the authors calculate approximately the heat of reaction for changing amorphous C into graphite, to be 1,480 cal. at 1,200°; 1,950 at 1,300°; 2,450 at 1,400°; and 3,200 at 1,550°.  It follows that the mean specific heat of amorphous C above 1,100° is higher than that of graphite, and that difference increased rapidly with the temperature.  No saturated hydrocarbon other than CH₄ was produced in any of the experiments.