The composition and distribution of such widely traded materials as obsidian, lapis lazuli, and copper have been studied, but many other materials have yet to be considered. This paper presents a broad study of a series of bituminous asphalts from Southwestern Iran. They were obtained from local natural sources, processed, transported, and fashioned into a variety of artifacts during the entire period from 6000 to 1500 B.C. We have examined a number of asphalt artifacts and some source materials by separating the bitumen and mineral portions, and examining each by classical techniques. During the millennia of burial, most of the hydrocarbons and much of the resins were lost from the bitumens, leaving a preponderance of asphaltenes. We have characterized the sources in terms of the proportions of limestone and in the mineral matter. Production increased markedly just before 3000 B.C., but without change in patterns of production and use.
Because of the lack of complete and accurate thermal decomposition data upon normal paraffins between hexane and hexadecane, the behavior of n-octane in the neighborhood of 570" C. and at atmospheric pressure was studied. The noctane was isolated from petroleum in quantities large enough to permit the determination of the amounts of essentially all its pyrolysis products. The effect of temperature, extent of decomposition, and nature of the apparatus in which pyrolysis was effected were studied. A slight revision of the free-radical theory improves somewhat its agreement with the experimental data. The effect of a carbonized surface upon the pyrolysis was studied, and the bearing of these results upon the theory of thermal decomposition is discussed. The liquid products obtained were thoroughly examined for evidences of rearrangement of olefins and of isomerization of the carbon skeleton. A semiquantitative analysis of all the chemical individuals found among the liquid hydrocarbons is presented. The probable manner in which they were produced, as indicated by the evidence available, is outlined. M ANY thorough researches upon the thermal decomposition of alkanes a t atmospheric pressure have been published recently, but nearly all of this work has been carried out upon the relatively simple gaseous members of the series. A certain amount of attention has been given to much larger alkanes. Hexadecane was extensively studied by Gault (1 7) and an approximately thirty-carbon paraffin by Waterman (50). However, because of the large number of gaseous and particularly of liquid products which result, complete and accurate analyses of all products have not been obtained as in the case of the small homologs. With the notable exception of the investigations of Frey and Hepp (15), little work has been done upon the pyrolysis of alkanes of intermediate carbon content. This is somewhat surprising, since efficient columns for the fractionation of gases (36) and liquids (IS), permitting analysis of the complex mixtures resulting from the decomposition of relatively small amounts of hydrocarbon, have been available for several years. To bridge this gap, the present work was undertaken; the compound chosen was n-octane.Several workers have reported preliminary studies upon n-octane pyrolysis; their results are condensed in Table I.The data are of little value because of the few accurate determinations of time and extent of decomposition. Such gas analyses as are reported show little concordance. Moldavskir (SO) observed that pressure exerted a marked influence on the pyrolysis and that iron exhibited a catalytic effect. Hugel and Szayna (19) obtained evidence of splitting at all carbon-to-carbon linkages of the molecule in nickel and iron apparatus. Decomposition in the presence of added catalysts has also been reported (IO, 28, 99, 35, 64). Much more thorough work by Dintzes and associates (6-8) coincided with the present study; similar experimental conditions were employed, with the single exception that decomposition was car...
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