2562 JONES AND WHEELER :CCXXXVIII.-The Compositioyh of Coal. Part 11.By DAVID TREVOR JONES and RICHARD VERNON WHEELER.IN a previous communication (this vol., p. 140) the result of distil-ling bituminous coal in a vacuum a t a temperature of 430° wasrecorded. It was noted that there did not appear t o be muchdifference in character between the liquid distillates obtained a tthat temperature and a t 350O. It seemed desirable t o examinefurther the character of the oils obtained a t a temperature notexceeding 350O.It will be remembered that on distillation a t 430° in a vacuum,bituminous coals yielded, besides gaseous products and water, about6.5 per cent. of their weight of tar. On distilling this tar, abouthalf remained a s pitch, boiling above 300O. The oils boiling below300° consisted mainly of unsaturated (ethylenic) hydrocarbons,40 t o 45 per cent.; naphthenes (C,H,,) and liquid paraffins, form-ing together about 40 per cent.; phenols, 12 to 15 per cent; andaromatic compounds, about 7 per cent.An examination of the corresponding oils obtained from thedistillates from coal in a vacuum atl 350°, details of which aregiven in the experimental part of this paper, showed them to con-tain the same compounds in similar proportions.The occurrence of aromatic compounds in the oils obtained a t thislower temperature requires explanation.I n accordance with a general theory respecting the compositionof "coal," put forward to explain the rapid formation of thevarious types of compounds found in coal distillates, the presencein coal was assumed of hydrogenated aromatic nuclei (or " bound ''molecules), which, i t was suggested, suffered decomposition, elimin-ating hydrogen, a t temperatures not much below 400°-the hmTHE COMPOSITION OF COAL.PART 11. 2563perature at which dihydronaphthalene has been found to decom-pose, thus:I n the light of the results recorded in the present paper, somemodification of this theory is required, so far as it affects thearomatic compounds.The mechanism of decomposition of santonous acid, Cl6HlOOs, asoherved by Cannizzaro (Gaaaetta, 1884, 13, 385), suggests an alter-native. This acid decomposes between 300° and 350°, yieldingchiefly 1 : 4-dimethyl-5 : 8-dihydro-&naphthol and propionic acid, inthe following manner :CMe CH, CMe Ci12/\/\ /\/\\/\/ \/\/Hoe$! # FH*CHMe*CO,H ~ Ho'g $ 1;' + CH,Me*C02HCH c CK, H C CHCMe CH, CMe CH,I n an analogous way, the formation of naphthalene derivativesfrom hydrogehated nuclei in coal can be explained:CH CH+ RH./\/\\/\/QH Q QHRCH C CH,CH CHAccording to this decomposition, elimination of hydrogen doesnot necessarily occur.Additional evidence of the occurrence of free pa.raffins in coal, t owhich reference was made in our previous paper, has been obtainedby Knecht and Hibbert (Mem.Manchestea Phil. SOC., 1913, 58,No. 2), who, in the course of a research on the soluble portions ofsoot., obtained a paraffin, C2,HS6, which they identified with hepta-cosane. This paraffin appears to be the same as that described byus as having a molecular weight intermediate between the valuesrequired for CfGHj4 and C271156 (Zoc.cit., pp. 141 and 143)2564 THE COMPOSITION OF COAL. I'ART 11.EXPERIMENTAL.One and a-half kilos. of a Durham bituminous coal, in piecesabout 0.3 cm. cube, dried a t 105O, were distilled in a vacuum a t350° in the manner dmcribed by Burgess and Wheeler (this vol.,p. 131). The temperature was maintained without interruptionduring ten days, a t the end of which time gas had practically ceasedt o be evolved. The coal was allowe'd to cool, removed f p m theretort,, well stirred, and replaced. Heating as before was thencontinued during seven days.The total amounts of tar, oil, and water collected were:Tar (No.1 receiver) ..................... 13.6 gramsOil (No. 2 receiver) ..................... 6-2 .. Water (No. 2 receiver) .................. 8.3 ..The yield of tar and oils a t 350° was thus 1.25 per cent. of theweight of coal used.The tar in No. 1 receiver had D:iO*9639. The aqueous solutionobtained on washing this tar gave with ferric chloride the colourreaction characteristic of o-dihydroxybenzenes, probably due t ocatechol, a substance that has been found by Bornstein to exist intfhe tars obtained on coking coal a t a low temperature.The oil in No. 2 receiver (which had been kept cool throughoutthe distillation by a solution of solid carbon dioxide in ether) hadThis oil was not further examined separately, but wasadded t o the €ar in No.1 receiver. The lower aqueous layer inNo. 2 receiver was found to contain hydrochloric acid, as was thecase in distillations of the same coal a t 430O.On washing the mixed t a r and oils with a solution of sodiumhydroxide, their volume decreased by 17 per cent. owing t o theremoval of phenols.The mixture was washed successively with (1) a dilute solutionof sodium hydroxide, (2) dilute sulphuric acid, (3) a solution ofsodium carbonate, and (4) water; and, after having been dried overanhydrous magnesium sulphate, was distilled. The compositionsand specific gravities of suc&ssive fractions of the neutral oils aretabulated below :0.8358.Fraction. 1. 2. Residue. - Boiling point ............ 170- 250" 250-300'DiE ........................0.8211 0.9066 0.998Hydrogen ............... 12.46 10-71 8.68Carbon ..................... 87.73 88.86 89.4 9Carbon+ hydrogen 100.19 99.57 98-17Fractions 1 and 2 were further examinedPHOTOKINETICS OF SODIVM HYPOCHLORITE S9LUTIONS. 2565Fraction 1 on being washed with concentrated sulphuric acidsuffered a reduction in volume of 44 per cent.., due t o t'he removalof olefines. Treatment with fuming nitric acid and weak fuiningsulphuric acid effected a further reduction in volume of about6 per cent., due, for the most part, t o the removal of aromaticcompounds. The oil remaining, after washing, drying, and distil-ling from sodium in a vacuum, had the following composition:Carbon ..................... 85.39Hydrogen .................. 14.93Carbon+hydrogen .. 100.32Naphthenes, (CnHZn), require C = 85.7 ; H = 14.3 per cent.Fraction 2, treated in the same manner as fraction 1, suffered areduction in volume of 56 per cent., due to the removal of olefines,and of 6 per cent., due t o the removal of aromatic compounds. Theresidual oil contained :Carbon ..................... 85- 44Hydrogen .................. 14.5 6Carbon + hydrogen 99.99The presence of aromatic compounds (naphthalenes) was estab-lished by aspirating the vapour from the oils, when heated a t looo,through an aqueous solution of picric acid, when yellow crystals of apicrate were deposited.EYKMEALS,CUMBERLAND