Modern Gasworks Practice

462 MODERN GASWORKS PRACTICE nuclei of a still more complex nature, leading eventually to carbon itself. The molecule of solid carbon in all probability consists of a very large number of carbon atoms arranged as a honeycomb of Condensed, benzene nuclei. These complex substances, still containing some hydrogen, are black and infusible, and their physical properties are very closely akin to those of pure carbon itself. Rhead and Wheeler, it may be noted, have pointed out that both graphite and amorphous carbon yield on oxidation a compound with the characteristic benzene nuclei in its Constitution. Some of the reactions which are responsible for naphthalene formation and which have been given by various authorities 1 are set down below:— (1) 5 C2H4 = C10H8 + 6 H2. (2) (a) 2 CH4= C2H2 + 3 H2. (6) 3 C2H2 = C6H6. (c) 2 C6H6 = C10H8 + 2 C + 2 H2. (3) (a) 2 C6H6 = C12H10 (Diphenyl) + Hs. (&) C12H10 + C2H4 = C14H10 + 2 H2. (4) 3 C6H6 — C14H10 + 4 C + 4 H2. (5) («) C6H6 + C2H4 = C6H5C2H3 + H2. (b) C0H5C2H3 + C2H4 = C10H8 + 2 H2. The most important work on the subject is undoubtedly that carried out by J. W. Cobb,2 who has studied the mode of decomposition of single constituents of the gas, chief attention liaving been given to benzene and toluene. The results obtained by this investigator are more fully referred to in the cliapter on Carboni-■zation, but briefly his conclusions clearly indicate that there is a tendency for hydrogen, which is the predominant product of carbonization, to reduce the single-ring benzene compounds to benzene, but at the same time to preserve the benzene nuclei intact. A similar action of hydrogen on the attached groups of more complicated ring Compounds most probably accounts for the production of naphthalene and atithracene. Hence the formation during high temperature conditions of the horizontal retort of a considerable quantity of the aromatic hydrocarbons and naphthalene, with. a •corresponding decrease in the yield of paraffins and phenols. VAPOUR PRESSURE OF NAPHTHALENE A knowledge of the vapour pressure of naphthalene in coal gas is of primary importance to gas engineers, for this permits an estimate to be made of the actual ■quantity of naphthalene which gas at a definite temperature will carry, and the quantity it will deposit when cooled from a higher to a lower temperature. The amoimt of naphthalene required to satur ate a given volume of gas at definite temperatures has been determined by both Allen 3 and Schlumberger.4 The results of these two authorities have been carefully checked by J. S. G. Thomas between temperatures of 0° and 60° C., and while Thomas is in substantial agreement with the figures given by Schlumberger, he differs at temperatures below 30° C. from results obtained by Allen. 1 American Gas Institute News, Sept., 1917. 2 Gas World, Sept. 7, 1918, p. 127. 3 J. Soc. Chem. Ind., 1900, 209. 4 J. für Gasbeleuchtung, 1912, p. 1257.