WATER GAS AND ITS RESIDUE By J. C. GODBEY, A. M. I THESIS Presented to the Faculty of Vanderbilt University for the Degree of Doctor of Philosophy JUNE, 1910 TENN. CONTENTS PAGE ACKNOWLEDGEMENT 5 INTRODUCTION 7 PART I. HISTORICAL 9 Water Gas Developement of the process of Water Gas Making 1 . The Present Method of making" Water Gas. The Composition of Water Gas. The Residue in Making Gas. The 1 * Gas Oil". PART II. EXPERIMENTAL 24 Comparison of the Physical Properties of the Tar and Oil. Distillation of the Tar. Distillation of the Oil. Effect of Light and Air on the Fractions. Specific Gravity Rate of Evaporation. Index of Refraction. Solvents. Effect of Lowering the Temperature. Chemical Analysis of the Tar. Distillation of the Tar. Analysis of the Distillates. The Residue. CONCLUSIONS 48 V V ACKNOWLEDGEMENT This work was begun in the laboratories of Van- derbilt University, and was carried on under the super- vision and with the assistance of Dr. J. T. McGill, to whom I wish to express my sincere gratitude and my appreciation of his untiring interest in my work. 330515 INTRODUCTION The manufacture of water gas is rapidly becoming a prominent industry. As a means of lighting and heating, the gas has already been accredited an equal rank with coal gas, and bids fair to supplant it. The present system of carburetting has removed the dan- gers of poisoning from an odorless gas, and has also produced a yellow flame suitable for lighting purposes. Ix can be cheaply manufactured on a small scale as well as on a large one. The one serious drawback, how- ever, is the comparatively useless residue which results from the process and which is known as water gas tar. Certain conditions in the manufacture of the gas result in a large yield of tar. Other conditions may produce a residue containing a high percentage of lamp black. The density of the tar seems to depend upon the kind of oil used, and the amount of tar varies ac- cording to the length of the "run." These complica- tions and the seeming relationship existing between the oil used in the run and the residue have suggested a comparison of the physical and chemical properties of the oil and the tar. These investigations were begun in the laboratories of Vanderbilt University in May, 1909. The material was secured at the plant of the Nashville Gas Com- pany and was taken from time to time during a space of nine months. It consisted of a number of specimens of oil used on different days and the residue on those days. The portions used for the comparative results of the physical properties of the oil and the tar were taken at the conclusion of a day's operating to make -7 sure that the tar had come from a certain known oil with which it might be compared. These precautions were taken because there seemed to be a difference in the oils used at different times. The oil used at the Nashville plant is all secured from the Standard Oil Company, and comes mostly from Indiana. In the preparation of this paper much information has been furnishd by Mr. T. J. Cunningham, editor of the American Gas Light Journal; Mr. D. J. Collins, of the United Gas Improvement Company; Mr. 0. 0. Thwing, chief engineer of the Western Gas Construc- tion Company; Mr. C. H. Houk, of the Standard Oil Company, and by many others. I wish to especially thank Mr. Blake, Assistant Superintendent of the Nashville Gas Works, and Mr. Johnson, Manager of the Nashville Chemical Company, for their cooperation and assistance, and for the many courtesies extended by them during these investiga- tions. 8 PART I HISTORICAL A WATER GAS. DEVELOPMENT OF THE PROCESS OF MAKING WATER GAS. Water gas had its beginning in a discovery by Cavendish. In 1784 he published his conclusions that "water consists of dephlogisticated air (oxygen) united to phlogiston (hydrogen)." 1 He further demonstrated that water is decomposed by passing it over redhot charcoal. Since hydrogen was one of the resulting gases, the product of the decomposition was combusti- ble. In the same year Mange, 2 Watt, 2 , Priestley 2 and Lavoisier 2 had also experimented with the decomposi- tion of water and had arrived at the same conclusions. It was almost a half century later, however, before a process for making water gas was perfected and pat- ented. In 1830, Donovan 3 patented a process for the decomposition of steam by passing it over redhot coke or charcoal. The gas was afterwards enriched with volatalized oils. Before this time several methods were employed for passing steam into coal gas retorts, but 'Phil. Trans., 1784, pp. 13-3 and 137. 2 Life of Cavendish Wilson. 3 Am. Glas Lt. Journ., Vol. XLI., p. 209. 9 Donovan's discovery is the first process for making carburetted water gas of which we have any mention. From 1830 to 1865 was a period of rapid develop- ment. Many different forms of apparatus were pat- ented, and some of the processes were given practical trials. Those of Selligue, 1 Jlobard, 1 White 1 and le Prince 1 probably being among the earliest of these. The first internally fired generator was patented by George Lowe 2 in 1831. The coke was heated redhot in a retort and allowed to fall into the generator, where the heat was raised by a natural draft, the top and bottom doors being left open. The doors were then closed and steam was admitted at the top. The water gas was taken off either from the bottom or at various heights where the fire was hottest. In 1859, Langlois 3 patented a process similar to that of Kirkham 4 (1852) . Tubular retorts were used, being heated by a natural draft admitted wherever the fuel bed needed it. Steam was allowed to enter at the top and the resulting gas passed into a mixing chamber, where it was carburetted. Schaeffer and Walcker, 5 of Berlin, took out a patent in 1860 for "a new process for the manufacture of water gas." The process, in the main, consisted of vertical retorts heated from below. The water, as steam, was admitted at the top, being decomposed as it 3 W.agner's Jahresbericht, Vol. V., p. 639. 2 Am. Gas. Lt. Journ., Vol. XLL, p. 209. 3 Wagner's Jahreshericht, Vol. V., p. 639. Mahresbericht der Chemie, Vol. 1859, p. 745; Annal de Chim. et de Phys., Vol. LI., p. 322; Polyt. Centralblat, 1859, p. 119. "Journal fur Gasbebuchtung, 1862, p. 63. Dingl. Journal, Vol. CLXIIL, p. 348. iPepert. de 'Chim. Appl., 1862, p. 245. Polyt. Centralblat, 1862, p. 623, u. 657. 10 passed downward. It was then taken off from below and carburetted with oil. The Fages 1 process employed the same kind of gen- erator as the Wilkinson and was known as the "Gaso- gene" process. It was patented in 1860. The appa- ratus was installed at Narboune and produced from 1,000 to 1,200 cubic meters of gas in twenty-four hours. Gillard's 2 system was also used at Narboune, but came several years later. In August, 1863, W. H. Gwynne 3 patented a process to be used in New York City. The steam, which was admitted at the top, was superheated by passing through pipes in the bench of double retorts. The gas was conducted directly into coal gas mains. The pro- cess was experimented with at Elizabeth, N. J. W. H. Strong, 4 in 1877, took out a patent for a process to be used in Brooklyn, N. Y. The vertical retort was used in this system also, but the steam was admitted at the bottom and passed upward through the heated coke. November 9, 1881, P. Jensen 5 patented a water gas apparatus in London. It consisted of one generator and two regenerators. These were heated very hot by the combustion of a portion of the water gas which had been produced. While one regenerator was thus heated, the steam was superheated in the other. The hydrocarbons were added by means of a shower of coal dust automatically regulated. 'Genie Industrielzeit, 1879, p. 385. Polyt. Centralblat, 1880, p. 1101. 2 d'Hurcourt, Deutsche Industrielzeit, 1868, p. 254. 'Wagner's Jahresbericht, Vol. X., p. 697. *Patentschrift, December, 1877. Deutsche Industrielzeit, 1879, p. 385. Industriel Blotter, 1879, Vol. XXVII., p. 417. Mourn. Soc. Chem. Ind., Vol. VIII., p. 533. 11 J. B. Archer 1 secured a patent for a new process on May 11, 1886. Steam was superheated to 1000 F. and then passed through an inter jector, where it draws with it a quantity of oil. The steam and oil are then heated to 2400 F., when they are converted into per- manent gas. The apparatus is composed of three con- centric, cylindrical casings enclosed in brick work and having the various necessary connections. In April, 1889, J. von Sanger and T. Cooper 2 pat- ented an apparatus with the producers arranged in groups. These producers could be operated with soft coal. The arrangement was presumed to lower the cost of water gas. The Tessie du Motay 3 process was one of the first practical systems. In it was introduced the "up and down run," which became a very valuable feature. The steam was decomposed in the presence of redhot coke. The "hydrogen," as the gas was incorrectly called, was stored in a tank or holder from which it was pumped ii-to an evaporator, where it was mixed with naphtha vapors. The water gas and the vapors were then "fixed." The increase in the cost of naphtha soon made the gas too costly for practical purposes. In 1900, J. G. T. Bormann, 4 of Berlin, patented a process in which the combustible gases were produced in a generator charged with ignited coke supplied with air enriched with oxygen. The gases were conveyed through a serpentine pipe arranged in the brick work of a chamber heated by a furnace. Steam was intro-* duced by another similarly set pipe, both pipes being Mourn. Soc. Chem. Ind., Vol. V., p. 471. Mourn. Society Chem. Ind., Vol. VIIL, p. 873. 3 Zeits Angew. Chem., 1894, pp. 137-142. Journ. iSoc. Chem. Ind., Vol. XIX., p. 614. 4 Journ. of Soc. of Chem. Ind., Vol. XXL, p. 102. 12 maintained at a temperature over 1200 C. This gas which entered the chamber was mainly carbon monoxide and hydrogen, the former acting with the steam to produce carbon dioxide and hydrogen. The hydrogen was drawn up into the upper part of the superheater, and then, together with the carbon diox- ide, was carried to a second generator containing incan- descent fuel, which received the carbon dioxide and the oxygen of the air through a grate in the side of the generator. The carbon dioxide was reduced to car- bon monoxide in this generator and a gas composed mostly of carbon monoxide and hydrogen was thus formed. Part of the gas produced in the first generator was utilized to heat the oxygen-producing apparatus. In 1902, E. Fleischer 1 patented a process for mak- ing "three quarters water gas." It had two separate blasts which were used in succession. The first pro- duced carbon dioxide and the second carbon monoxide. Ordinary coal was used in the generator. G. Horn 2 employed the vertical retort, but varied its height according to the kind of combustible used. It could be arranged for either finely powdered coal or a spray of oil. Superheated steam was passed through a side of the decomposing chamber, made of grating. The process was patented in May, 1903. The chief feature of the system was the continued production of water gas. Other processes having this feature were those of F. Bauke and C. Fuchs 8 (1903) and H. Kop- pers 4 (1901). 1 U. ,S. Pat. 701,556. Mourn, of Soc. Chem. Ind., Vol. XXV., p. 1212. 8 Pr. Pat., 329,028. Eng. Pat., 13,047. 13- In May, 1903, L. Guenot 1 patented an apparatus v/hich automatically regulated the change from "make" to "blast" by the rise and fall of the gas holder. At the lower end of the producer were two inlet pipes and at the top one outlet pipe leading to a flue. These three pipes were connected by water-sealed bells attached to a lever. The rise and fall of this lever regulate the valves. The chief feature of the Thurman 2 process (1904) is the way in which the generators are connected in pairs during the "blast" and in series during the "make." If carburetted gas is to be made the inlet valve for the hydrocarbons is also connected to the air valve. The air and water gas which remain in the bot- tom of the generator and the ash pit are expelled with steam at the end of each phase. The process almost exclusively used at the present time is the T. S. C. Lowe 3 process. He first perfected the vertical, internally-fired generator with the direct- ly-connected carburetter and superheater and the hy- draulic seal. He began his experimenting as early as 1875, and is still continuing it. The Nashville plant employs the Lowe system, which will be described fully under "The Present Method of Making Water Gas." Opposition 4 was very bitter against water gas be- fore 1885. It was even legislated against in some States and cities. But the present methods of car- buretting and of mixing the gas in coal gas mains has J Under Internat. Com., May 14, 1903. 2 Fr. Pat., 342,578. Journ. Soc. Chem. Ind., Vol. XXIII., p. 930. 3 Wagner's Jahresbericht, Vol. XXV., p. 1204. Journ. Soc. Chem. Ind., Vol. XIX., p. 614. Mourn. Soc. Chem. Ind., Vol. XIX., p. 614. Science, Vol. V., p. 303. gradually overcome this opposition. In the year 1909 80%' of the gas used in the United States was water gas. THE PRESENT METHOD OF MAKING WATER GAS. The apparatus used in the manufacture of water gas are divided into two classes ; first, those that pro- duce the blue water gas only, which is used just as produced or carburetted separately ; second, those that produce carburetted gas directly. The plant on Four- teenth Street, New York City, is an example of the former; the one at Nashville, Tennessee, employs the latter. The blue water gas system produces no residue. We will, therefore, confine the description to the car- buretted water gas apparatus. For convenience it may be divided into six parts: (1) The Gnerator, (2) Carburetter, (3) Superheater, (4) Hydraulic Seal, (5) Scrubber, and (6) Condenser. Figure I is an illustration representing these divisions and also showing the many minor parts, such as fans, sprays, drains and connections. The Generator. The purpose of the generator is to produce the pure water gas which burns with a non- Liminous flame, or a faintly bluish one, and possesses no odor. The pure gas is simply hydrogen and carbon monoxide theoretically in equal proportions. The gen- erator is a cylindrical steel shell of varying size and lined with a double layer of fire brick, and having a grate to support the fuel which is poured in at the top. In the side and near the bottom are doors for removing ashes and to serve as manholes when repairs are needed. The generator is filled with coke to a 'Sci. Am., Vol. LXLVIL, p. 263. -15- depth of seven to ten feet. This is fired to an incan- descent heat. Steam is then sprayed upon the carbon, which has a great affinity for oxygen, hence H2 is lib- erated from the HteO and C and combine to form CO and 02. The amount of the C02 depends upon the degree of heat, depth of fuel, and amount of H2O admitted. The per cent must be kept low since the presence of the inert 002 lowers th candle power and reduces the calorific value of the gas. It is generally estimated that every per cent of 02 reduces the power one candle. There are three reactions that take place: 2H20+C=C02-f2H2. H20+C=0+H2. C02+C=CO+CO. It was demonstrated by Dr. Bunte, 1 of Germany, that the reaction producing 002 takes place from 600 700 C 2 , and that it is only at a temperature of 1000 C that CO is formed. Hence the spray of steam roust be of short duration, because it tends to lower the temperature of the coke in the generator and produce C02. To restore the high temperature a blast of air is forced through the coke by means of a fan run at a regular speed. The oxygen of the air unites to form, first, C02, then CO as it comes in contact with the upper layer of coke. And the proportion of C02 again depends upon the amount of air admitted in the "blow," depth of fuel and temperature. There is always more CO during the latter part of the "blow." It is also essential that the steam be very dry so that no water l Sci. Am., Vol. LXLVII., p. 263. -See also Journal of the Chem. Soc., Vol. XLVIII., p. 1636. -16- is sprayed upon the coke to cool it. A trap for freeing the steam from water is generally employed and the pipes are well wrapped with asbestos. The Carburetter. In shape and size the carbu- retter is very much like the generator. It is filled with firebrick arranged in checker work. The gas passes from the generator into the carburetter and the heat of the "blow" is utilized to raise the temperature of the bricks. When the temperature is thus raised a spray of oil is admitted and, being vaporized, mixes with the water gas to enrich it. The Superheater. The superheater is very much like the carburetter and is a continuation of the "fix- ing'* process. At its top is the stack valve, which is opened during the "blow." The superheater is heated by the same process and at the same time as the car- buretter. The Seal. From the fixing chamber the gas passes into the seal. This is a tank of water kept hot by a continuous flow from the boiler. The gas bubbles through the hot water which serves to cool out some of the residue which settles to the bottom. The gas is somewhat cooled, also. The Scrubber. As the gas bubbles through the seal it passes into the scrubber. This is a cylindrical tank filled with wooden trays kept moist by a spray of water. Here the greater part of the tar-like residue is "scrubbed" out of the gas by contact with the trays. It settles to the bottom of the scrubber and is carried off by drains. The Condenser. The last process before purifica- tion, through which the gas passes, is the condenser. In it the gas comes in contact with rows of water-cooleej pipes which free it from any remaining tar and cool it for the relief holder. In the condenser, and also in the "washer," it loses still more of the tar and heavy oil residue. The last cleaning process is to free the gas from EteS by passing it through a tank of iron oxide and sawdust. Finally it is carried to the relief holder and ready for distribution. THE COMPOSITION OF WATER GAS. Water gas varies in composition according to the process of manufacturing. Some times the gas is made and subsequently carburetted as in the Dellwick- Fleischer process 1 (1896). Usually, however, the car- buretting is carried on as the gas is made. The follow- ing analyses show the composition of the gas: 1. The Dellwick-Fleischer, Uncarburetted. 2 Carbon dioxide 4.65 Heavy hydrcarbons .05 Oxygen 20 Carbon monoxide 39.65 Marsh gas 82 Hydrogen 50.80 Nitrogen 3.83 2. The Carburetted. 3 Carbon dioxide 3.4 Illuminants 12.3 Oxygen 5 Carbon monoxide 29.1 Hydrogen 30.3 Marsh gas 21.3 Nitrogen .3.1 'Am. Gas. Lt. Journ., Vol. XCI., p. 222. Wagner's Jahresbericht, Vol. XLIII. 2 Sci. Am., Sup. Vol. LJL, p. 21706. 3 Cci. Am., Vol. LXXXIV., pp. 39 and 102. -18- 3. The Carburetted. 1 Hydrocarbon vapors 1.2 Carbon dioxide 3. Heavy hydrocarbons 12.6 Oxygen 4 Carbon monoxide 28.0 Hydrogen 31.4 Methane 20.2 Nitrogen 3.2 THE RESIDUE IN MAKING WATER GAS. The residue is called tar because of its resemblance tc coal tar. It is, however, of a much lower specific gravity and a much less viscosity, besides many other differences. In the process of gas-making the tar is given off at four places. First, that which cools out in the hydrau- lic seal; second, the portion that condenses in the scrubber ; third, the part that collects in the condenser, and, fourth, that which cools out in the "purifier." In each case the cooling is carried on by means of a flow of water. A steady stream of water passes through the seal and hence there is much water in this residue; the scrubber is constantly washed with a spray of water which mixes with the condensed tar. The pres- ence of this large quantity of water is one of the chief sources of difficulty in trying to utilize the residue or in attempting to work with it. There is very little difference in these various resi- dues when the process is correctly operated. That which condenses out of the seal often contains more or less of the gas oil which has gone through the process un cracked. Various means are used to detect the oil. The greatest percentage of tar comes out in the scrub- 'Jnternat, Library of Tech., Vol. XX., Sec, 52, p. 2, -19- ber. It collects on the wooden trays some times in such quantities as to impede the process of gas-making. As it cools it runs down into a receiver, where it is col- lected at the bottom of a tank from which the cooling v/ater of the scrubber constantly overflows. Being heavier than the water, the tar sinks to the bottom. Specimens from this tank were used in the experi- mental part of this research. The tar from the condenser is the same as that from the scrubber. Some little residue cools out in the puri- fying process, but this is contaminated with the iron and sawdust. The character of the residue may depend largely upon two things: First, the kind of oil used in the "run"; second, the way in which the process of gas- making is regulated. If the "run" is long and the "blow" short, the quantity of tar will be large and of a lower specific gravity. It will contain more heavy hydrocarbons and more of the original oil. If the "run" is short and the blow long, the tar will be less in quantity, of a higher specific gravity and a greater viscosity. More free carbon in the form of lampblack will be present and the quality of the tar will be much inferior. The gas will also be less in quantity and poorer in quality. The greatest of care must be exercised in deter- mining the length of time of the "run." In some plants a specially constructed pyrometer is used to keep the temperature constant and uniform. But more often the operator depends upon his ability to judge of the temperature with the eye. As yet very little use has been found for the tar. It is usually pumped into a tank above the furnace and -20- used to spray the coke with which the furnace is fed. It burns with a heavy smoky flame. THE "GAS OIL." The oil used to enrich water gas is a product of petroleum. It is almost universaly furnished by the Standard Oil Company, and consists of the residue which remains after the illuminating oils have been distilled off. It is a very dark, heavy oil, with the odor of lubricating oil. It is supposed to come off above 250 C, but the incomplete process of distillation leaves some of the lower boiling fractions. Crude petroleum contains almost all of the paraffin series as follows: Gases Methane Formula C H4 C 75.00 H 25.00 Boiling Point Sp. Gr. .559 Ethane .C2 H6.. .80.00. . . .20.00. . . . . .5516 Propane 3 H8 81.81 18-19 20 C 1.522 Butane . C4 Hio. .82.80. . ..17.20. . 1C . . . .6(0C Liquids Pentane C5 Hi2 83.33 16.67 37C .628 Hexane C6 Hi4 83.72. 16.28 . 69C . .664 Septane .07 Hi6. .84.00. . . .16.00. . . . 97.5C.... . . . .699 Octane Nonane Decane Undecane . . . Dodecane. . . . .08 Hi8. .C9 H20. .ClO H22. .Cn H24. .Ci2 H26. .84.21. . .84.38.. 84.51. . .84.61.. .54.70. . . .15.79. . ..15.62.. . .15.49. . . .15.39. . . .15.30. . . . 125C . . 136C . . . . 158C . . 182C . . 198C ... .703 ... .741 ... .757 ... .765 . . . .776 Tridecane Ci3 H28 84.78 15.22 216C .792 Tetradecane Ci4 H3O 84.85 15.15 238 C .812 Pentad e cane. CIS [32 84.90 15.10 258 C .825 Hexadecane Ci6 H34 84.94 15.06. . 180C .828 Solids Paramyricyl . Paracryl . 027 Hs6. .630 H62. .85.26.. .85.31.. ..14.74.. . .14.68. . '. ' 370C .... It will be seen from a study of this table that the gas oil would consist chiefly of those compounds above Decane (CioH22), which are either liquids or solids 'Internal. Library of Tech., Vol. XX., Sec. 52. 21 with high boiling points. The gas oil varies in specific gravity from .770 to .859, this corresponds to the spe- cific gravity of the compounds of the Marsh gas series above Decane. The imperfect distillation precludes a complete separation, however, hence the presence of some of the series blow 250 C. The products of crude petroleum used commer- cially are : 'Product. Boiling Point Natural gas Gas Rhigolene 0C Gasoline 50, 70, 98, 110C Kerosene 150, 300C Lubricating Oil Above 300C Vaseline Solid Paraffine Solid The substances known to commerce which are con- tained in gas oil would be kerosene, lubricating oil, vaseline and paraffine. The amount of oil used at a "run" varies according to the length of both the "run" and the "blow." At the Nashville Gas Company's plant about thirty-two gal- lons is used each time. The oil is sprayed into the carburetter after having been heated by passing through pipes incased in steam jackets. The tempera- ture being very high in the carburetters, the oil is at once "cracked." After this instantaneous vaporization it passes on through the various phases of the process. The table on the adjoining page is a facsimile of a daily report at the gas works and is printed by the permission of the Nashville Gas Company. It shows the time consumed in the "run" and in the blow," the amount of oil used each time, the frequency with which the generator is fired with coke. Thirty-eight pounds of coke and four gallons of oil are used to pro- 22 duce 1,000 feet of gas. A daily run will produce 400,- 000 feet of gas and 750 gallons of tar. The tar varies, however, from twelve to fifteen barrels. This report would show better results if the plant were running steadily every day. According to the present system it is operated only when the supply of coal gas is getting short and a quick replenishing of the holder is needed. apew seg J8PIOH janay jajaw uojws xapui maw l!0 10 d -3 unyuMOQJOdn Suiueaio pasn axoo pasn no UO uny '"IW mJ H P% a a a MB o o Ml o O o o O G fl G " a c UJ O a M 3^5 J3 JH J^ o UJ az 0) a c .2 4) 44 c o rt ,0 UH ***C o o ^ be & id ^y *~ * 2 ^ o 3 bo ,0 cd i 1 2 3 * b^ . ^ > u. ce o o .22 rt 13 t 0) 44 3 ark reddish ark reddish O (4 3 1 3 *d ddish brown rt E j*^ *o *d CU 4> IH IH a> /s 'o ^> 9) 4) 0) v _J S 8 S 13 3 3 3 3 ^ B o 3 >> tf) in & >% t /% fS ^s /s 5 G c; 4) ri i S s i S 0) JH" Z3 IS 3 I 1-H ^ D 4) ^* V 4) az 3 O ^J g ^ ^3 2 < h 1 I 1 1 c3 'o OB 1 i 3 o 6 IH _e SOLVENT Water trb. bisulphi arb. tetrach: ride. Benzine Acetone Cuminol troleum UJtl Parafine OI *o o 53 tt O O The various solutions were stoppered and set aside for thirty-six hours. The carbon bisulphide in which the oil had been dissolved became brownish to a slight degree, while the tar solution had become black. When filtered the filtrate came through black. The carbon tetrachloride-oil solution had also deep- ened in color, and the tar solution had become black, filtering black also. The benzine in which the oil had been dissolved changed from a clear solution to a brown ; that in which the tar was dissolved became a deep black with a reddish hue. It filtered black. The cuminol-oil solution also changed from a clear to a brown. The tendency of all the solutions of both the oil and the tar was to darken upon standing. The tar, how- ever, showed a more decided tendency to deepen in color. All of the tar solutions are a deep red or reddish black, while most of the oil solutions are either clear or only slightly brown. Upon filtering the tar solutions the filtrate remains a very deep color, showing that the coloration is not due to particles of carbon held in suspension. This conclusion is verified by the deepening of the color upon long standing rather than a settling out of the carbon as a precipitate should it have been held in suspension. EFFECT OF LOWERING THE TEMPERATURE. An apparatus for surrounding the tar or the oil with ice and salt was prepared (see Fig. Ill) as fol- lows: An inverted bottle (a) having the bottom cut off was used as the outer jacket; a long, parallel- walled 30- -A- funnel (b) was inserted through the stopper; the lower end was connected with an aspirator; (c) over the end of the funnel was placed a filtering cloth; (d) when the temperature of the liquid had been lowered a gentle pressure was exerted by means of the aspirator pump. The temperature thus obtained was not sufficiently low to cause a distinct separation of solids from either the tar or the oil. At C. the tar was unaffected, but the oil had become viscid. At -4 C. the tar was still unaffected, while the oil had congealed to a semi-fluid mass. At -12 C. the tar showed a slight change. The oil, however, had frozen solid and would not spill from an inverted vessel. A slight pressure was then exerted by means of the aspirator and an unsolidified liquid was forced out. A comparative test of this liquid and the frozen portion in the funnel showed no difference in specific gravity nor index of refraction. The various distillates of the tar and oil were then placed in a mixture of salt and ice at -8 C. All of the fractions of the tar remained unaffected. I., II., III. and IV. of the oil were also unaffected, but the higher boiling fractions, V. and VI., froze solid. CHEMICAL ANALYSIS OF THE TAR. ANALYSES ON RECORD. Lieberman and Burg 1 passed the heavy oils of petro- leum through iron tubes heated redhot and obtained hydrocarbons of the aromatic series. They also at- tempted to show a similarity between these hydrocar- bons and coal tar. Experimenting along the same lines 'Berichte der deut. Chem. Gesel, 1878, p. 273, -31- Salzman and Wichelhaus 2 later came to the same con- clusion. L. Premier 3 treated paraffin residues and certain fractions of petroleum coming off at a very high tem- perature with -bromine and found that these high boil- ing products readily absorbed bromine and contained aromatic hydrocarbons. Matthews and Gouldon, 4 in an analysis of the tar from water gas carburetted with Russian oil, obtained the following results: Benzine 1.19% Toluene 3.83% Light Paraffine 8.51% Solvent -Naphtha 17.96% 'Phenols Trace Middle Oils 29.14% Creosote Oils 24.26% Napthalene 1.28% Anthracene (crude) 0.93% Coke 9.80% Total 96.90'% In 1882, Dr. A. H. Elliott 1 began an analysis of v-ater gas tar from gas carburetted with naphtha. He found a large percentage of naphthalene and 2.63% of anthracene, but mentions no other constituents. The following table shows the result of his distilation: Temperature . Weight of Distillate degrees Celsius from 100 Volumes 80-200 9.2 1-3 Oil 2-3 Solid 200-270 11.2 Solid 17.7 Oil 270, Pitch 6.0 Solid 26,5 Oil Last Fraction 1.7 Semi-solid 6.0 Oil Total ..78.3 'Am. Chem. Journ., Vol. VI., p. 248. 2 Berichte der deut. Chem. Gesel, 1878, p. 431. 3 Am. Chem. Phys., Vol. XVIL, p. 5. Journ. Chem. Soc., Vol. XXXVL, p. 1025. 4 Gas World, Vol. XVI., p. 625. -32- The naphtha used to enrich the gas from which the comes in the above analysis is that fraction of petroleum which comes over below 150 C. In the present system of carburetting the oil used is the frac- tion above 250 C. It is that portion of crude petro- leum which remains directly after the illuminating oil distillate has been taken. This oil is known to com- merce as gas oil, and is used at the Nashville Gas Works. DISTILLATION OF THE TAR. In order that larger quantities of the various frac- tions of the tar might be obtained for experimental purposes, a number of distilations were conducted at the works of the Nashville Chemical Company. A f ourteen-gallon still was provided and so arranged that the flames could heat the sides and bottom uniformly. A hole was bored in the top, in which was inserted a glass tube sealed at the lower end. In this tube the thermometer was placed. The still was also provided with a condenser and a long delivery tube. In the final distillation, the fractions of which will be referred to in this discussion, the following fractions were taken: I. Up to 160C. V. 265-295. II. 160-210. VI. 295-335. III. 210-245. VII. 335-365. IV. 245-265. VIII. 365 solid. Water was found to be present in fractions I. and II., but only traces above that, the total percentage be- ing between 8.6% and 9%. In former distillations v, Ith inferior material as much as 19.3% to 20% of water was found to be present and came over with almost every fraction. -33- The water was always decanted before the tar was placed in the still, but some of it was held in suspen- sion. This was liberated only upon heating strongly. Douglas 1 succeeded in dehydrating the tar by heating it in a closed boiler under ten atmospheres pressure, leaving only 1% of moisture. 27.27 liters of the tar were placed in the still and the heating was carried on very slowly at first. The flow from the delivery was kept uniform. Toward the last the water in the condenser was drawn off so that the higher boiling oils would come over freely. The total time consumed in the distillation was nine hours. The following table gives the results of the distilla- tion on the larger scale: Range in Specific Amt. in Cubic Fraction Temp. Gravity Centimeters Percentage Water 1.0020 2350 8,62 1. Up to 160C .8854 1900 6.61 2.160 210C .9219 2350 8.62 3. 210 245C 4. 245 265C .9624 2600 5. 265 295C .9795 2500 6.295 335'C .9940 3650 7 335 365C 1.0342 3700 Residue 5850 Total 25900 90.95 ANALSIS OF THE DISTILLATES. The Water. The water which came over in fractions I. and II. was separated from the tar distillate by means of a separatory funnel. When thoroughly freed from tar Mournal of Gas Lighting, 1891, p. 1130. -34- it had a faint greenish blue color, a weak alkaline reac- tion, and a specifis gravity of 1.0020 at 28 C., water at 28 being taken as the standard. A small quantity was warmed with NaOH in a closed flask with a small de- livery tube. An ammoniacal odor was detected and red litmus was turned blue. 500 cc. of the water was acid- ulated with hydrochloric acid and allowed to stand for twenty-four hours. At the end of that time a deep blue precipitate had settled out. This was filtered, washed with water containing a few drops of hydro- chloric acid and the precipitate dried at 100 C. A portion of the precipitate fulfilled the following test for ferric-ferrocyanide Fe4(FeCy6>3, Prussian blue. It is soluble in concentrated acids but reprecipitated upon dilution; 1 soluble in ammonium tartrate; 2 soluble in oxalic acid, but entirely reprecipitated when exposed for a time to sunlight. 3 When strongly heated it glows and is reduced to ferric oxide, Fe203/ It is insoluble in water, alcohol and dilute acids. 5 These tests were further confirmed by subjecting the brownish residue which remained after the pre- cipitate had been heated to redness, to the following; dissolved in hydrochloric acid and a portion tested with potassium f errocyanide ; a deep blue color. Another portion was tested with potassium-sulpho-cyanide ; a red color. A third portion was made alkaline with ammonium hydroxide ; a deep blue color. These prove the base to be iron. A portion of the precipitate was 1 Watt's Chem. Die., Vol. II., p. 289. 2 Berichte der deut. Chem. Gesel, Vol. VIII., p. 1503. "Berichte der deut. Chem. Gesel, Vol. III., p. 12. *Watt's Chem Dis,, Vol. II., p. 289. B Ibid, -35-^ subjected to Lassaigne's test 1 for nitrogen, sulphur and the Halogens Nitrogen was the only one found to be present. Besides the ferric-ferrocyanide there may be present ferrous ferrocyanide and ferrous-ferricyanide, since ferric salts oxydise ferro- to ferri-cyanides, while ferrous salts reduce ferri- to ferro-cyanides. 2 A small amount of cyanogen which is probably present in the gas as hydrocyanic acid, acts upon the oxide of iron, formed by the action of the oxygen on the sides of the generator and carburetter, to produce iron cyanides. This cools out in the scrubber and hence is found in the tar. The filtrate was then evaporated to dryness and left a brownish residue. A portion of this was heated to redness on a platinum foil. It burned with no flame and left a brownish red residue which was tested for inorganic substances and found to be ferric oxide, Fe2O3, and ferric chloride, Fe2C16. In an analysis of the gas from the gas plant iron was found to be present, 3 probably in the form of iron carbonyl, FeCO, or iron pentacarbonyl Fe(CO)5. Iron carbonyl has also been found in water gas and coal gas which has been compressed in iron cylinders. 4 The existence of a volatile compound of iron has been known since 1891, in which year it was discussed by Dr. F. Quincke before the British Chemical Society. 5 When iron is brought in contact with hydrogen gas and then treated with carbon monoxide the issuing gas is found to contain iron. When this gas comes in 'Carbon Compounds Weston, p. 3. ^Berichte der deut. Chem. Gesel, Vol. VIII., p. 1503. 3 Analysis of Dr. W. H. Hollinshead, 1909. 4 Proc. Chem. Soc., 1891, p. 126. 5 Journ. Chem. Soc., 1891, Vol. LIX., p. 604. -36- contact with aliphatic oils the iron compound is par- tially absorbed, but is decomposed upon exposture to the air, with a separation of iron hydroxide. 1 Further- more, a trace of iron-tetra-carbonyl, Fe 464 has been found in mineral oils. 2 Iron hydroxide being soluble would appear in the filtrate of the water as an iron chloride. A portion of the residue from the evaporated filtrate was partly dissolved in absolute alcohol. After stand- ing a few days the alcohol evaporated, leaving a brown- ish colored residue. Cubical crystals separated out of a water solution of this brownish residue. These when burned gave off a vapor and seemed to indicate the presence of an organic base which has not yet been determined. Fraction I., 160 sp. gr. .8854, 6.61%. 500 cc. of fraction I. was dried with calcium chlo- ride and refractionated, using the hempel three-bulb tube and completing each fraction as in the distillations on a small scale. Fraction Range in Temp. Amt. in C. 'C. 1. 60 100C 65 2. 100 120C 93 3. 120 160'C 184 Residue above 160 C 158 These fractions were again refractionated, giving the following results: Fraction 1 : Fraction Range in Temp. Amt. in C. C. a. 60 80C 2 b. 80' 85C 27.5 c. 85 100C 20 Above 100>C 15.5 Mourn. Chem. Soc., Vol. LIX., pp. 605 and 1090; Treatise on Chem., Roscoe and Schorlmner, p. 1019. Mourn. 'Chem. Soc., Vol. LIX., p. 1093. 37 Fraction 2-1- residue from 1. a. 85 100 C 35 b. 100 105C 10 c. 105 115C 40 d. 115 120C 22 Above 120C 1.5 Fraction 34- residue from 2. a. 120 130C 57.5 b. 130 150'C 83 c. 150 160C 10 Above 160C 32 Fractions la and Ib were tested for carbon bisul- phide according to the method devised by Nickels. 1 A portion of the distillate was treated with a solution of potassium hydroxide in absolute alcohol (1 g. in 20 cc) and the mixture agitated thoroughly. But no potas- sium xanthate, K2C2H5(CO)S2, separated out nor did the solution become yellow. Thiophene, 2 641148. Fraction Ib was tested for thiophenes by means of the indophenin reaction. 3 The mixture of isatin and strong sulphuric acid was turned blue, indicating a trace of thiophene. If present in larger quantities the color would have been a brown. This reaction is also characteristic of thiophenic acid, C4H3 SCOOH, or de- rivatives of thiophene. Benzene, C6H6, b. p. 80-82. Fractions Ib, Ic and 2a were treated with benzene as follows: 4 Thoroughly agitated with concentrated sulphuric acid, keeping thoroughly cooled, until fresh x Chem. News, Vol. XLVIII (1881), p. 148, 250. Ibid, Vol. L (1885), p. 170. 2 Berichte der deut. Chem. Gesel, Vol. XVI., p. 1465. Coal Tar and Ammonia, Lunge, p. 190. Commercial Organic Anal., Allen, Vol. II., ph. 2, p. 164. 4 Ibid, Vol. II., part 2, p. 157. 38 quantities of the acid are not blackened upon continued shaking. Wash with water and sodium hydrate. Again wash and dry with calcium chloride. Distill and collect the portion which comes over below 90 separately. This fraction was redistilled and almost the entire frac- tion came over at 80-82. The fractions were then cooled to C., and this one froze solid. A few drops of this distillate were mixed with 1 cc. of nitric acid (sp. gr. 1.42) and 1 cc. of sulphuric (sp. gr. 1.84) and heated to boiling for thirty seconds. The mixture was poured into cold water, filtered, washed with alcohol and crystallized from alcohol in fine, nearly white needles, which melted at 89.50, the melting point of dinitro benzene. 1 When treated with concentrated H2S04 fraction Ib lost 67% by volume, while fractions Ic and 2a lost nearly 90%. 16 cc. of benzene, m. p. 80-82 was ob- tained from 500 cc. of fraction I., being 0.22% by volume of the tar. Toluene, C;H8, b. p. 111. Fractions 2a, 2b and 2c were thoroughly agitated with concentrated sulphuric acid till fresh acid was no longer darkened, washed with water and sodium hy- droxide and dried over calcium chloride and redistilled. 2 The portion from 110-112 was collected separately. 'Ihe fractions were risdistilled and cooled to C., but no sign of congealing or crystallization appeared after standing twenty-four hours at this temperature. Three drops of the hydrocarbon were mixed with 1.5 cc. of fuming nitric acid and 1.5 cc. of fuming sulphuric ^dent. of Pure Organic Comp., Mulliken, p. 200. 2 Coal Tar and Ammonia, Lunge, p. 623. 39 acid. After thirty seconds the reaction mixture was poured into cold water, filtered, washed with alcohol and recrystallized from alcohol in nearly white needles, which melt at 70.5 C., which is the melting point of dinitrotoluene. 1 When treated with concentrated sulphuric acid fraction 2c lost 66.3% by volume. 2a and 2b lost 95%. 8.8 cc. of toluene was gotten from 500 cc. of distillate 1, or a total of .11% of the tar is toluene. Xylene; CSHio b. p. 138-142. Fraction 3b was treated with 120% of concentrated sulphuric acid and shaken up for thirty minutes. It was then washed with sodium hydroxide and water, dried over calcium chloride and redistilled. Para- xylene 3 being insoluble in cold concentrated sulphuric acid is unattacked but the meta- 4 and ortho- 5 xylenes form soluble sulphonates and can be separated from the sulphuric acid solution. 6 Dilute the solution with water, neutralize with barium carbonate, 'filter off the barium sulphate, concentrate the filtrate by evap- oration, and divide into two parts. Set one portion away and allow the barium salts to crystallize. Treat the remainder with a slight excess of sodium carbon- ated, and concentrate by evaporation. After standing ^Edent. of Pure Organic Comp., Mulliken, p. 202. 2 Am. Chem. Pharm., Vol. LXIX., p. 162. Ibid, Vol. CLXXXVL, p. 331. Journ. Prakt. Pharm., Vol. LXL, p. 74. Ibid, Vol. LXX., p. 300. 3 Treatise on Chem., Roscoe and Scharlemmer, Vol. III., part 4, p. 388. Coal Tar and Ammonia, Lunge, p. 156. Berichte der deut. Chem., Gesel, Vol. IX., p. 405. 4 Ibid, Vol. X., p. 1010. 5 Ibid, Vol. CLIIL, p. 265. Treatise on Chem., Vol. III., part 4, p. 388. 40 for several hours large prism shaped crystals of so- dium ortho-xylene sulphonate 1 C6H2 (CH3)2 SOs Na+ 5H20, crystallize out. A portion of the crystals were treated with hydrochloric acid, nitrated with fuming nitric acid crystallized from alcohol and the melting point taken. 2 Since sodium meta-xylene sulphonate does not crys- tallize it was separated from the filtered solution by means of HC1, nitrated, and the melting point of the nitro compound taken. The portion of the xylene which did not form a sul- phonate was washed with water and sodium hydrate redistilled, and a few drops nitrated 1 as follows : Boiled with 1 c.c. of fuming nitric acid and 2 c.c. concen- trated sulphuric acid, for 1 minute. Poured into cold water, filter, wash with alcohol. These crystals were clusters of white needles, which were trinitro para- xyleneC6H (CH 3 )2 (N02) 3 . 2 The amounts of para- meta- and ortho-xylenes in xylene have been variously estimated. Usually, how- ever, meta-xylene has the largest percentage and ortho- the smallest. Levinstein 5 has found in various sam- ples of crude xylene: Paraxylene 3 10% Metaxylene 70 87% Orthoxylene 2 15% Paraffine 3 10% When a mixture of the three xylenes is treated with bromine containing 1% of iodine, they are converted into the tetra-bromo-xylenes, C6Br4(CH3)2. If treatise on Chem., Vol. III., part 4, p. 388. 2 Ident. Pure Org. Comp., Mulliken, p. 203. 3 Ident. Pure Org. Comp., Mulliken, p. 202. 4 Berichte der deut. Chem., Gesel, Vol. X., 1010; Xi., 22. 5 Ibid, Vol. XVII., p. 444. 41 heated to 160-170 this yields the tetra-brom-phthalic acids quantitatively; C6Br4 (CH3)2-f 6Br2+4H20=C6 Br4 (C02H)2+12HBr. Since these can be readily separated, the composition of the original mixture can be determined in this way. 1 Fraction 3b when refractionated yielded 20 c.c. be- tween 136-142. This is 4% of fraction I or .27% of the tar. Of this amount para-xylene represents .05%. Cumene, C6H3(CH3)3. An effort to determine the presence of trimethyl benzene resulted in a sulphonated product of distillate 3b, but since little is known of cumene, no satisfactory qualitative tests were applied. Cumene has been found in crude petroleum. 2 Ferric ferrocyanide was found to have come over in the low boiling fractions of distillate I. and sepa- rated out of the dilute sulphuric acid solution. Its pres- ence was not detected above fraction 3b. Fractions II. and III., 160-245, 6.82% sp. gr. .9219. 500 c.c. was refractionated as follows : Fraction Range in Temp. Amt. in C. C. 1. 100 160C 67 2. 160 200C 181 3. 200 211C 102 4. 215 235C 95 5. 235 245C 14 Residue above 245C 37 Refractioning. Fraction 1. a. 100 120C 9 b. 120 130C 16.5 c. 130 150 C 22.5 d. 150 16$'C 10.5 Above , 160 C 8.5 'Compt. rend., Vol. CI., p. 1218. 2 Am. C. .1 gram of the crystals was treated with picric acid and the melting point of the long hair like needles separating out, was found to be 150.5, which is that of naphthalene pic- rate, CioH4C6H 4 (N03)20 1 . Fractions II. and III. yielded 1.28% of naphthalene, the greater part coming over in fraction 4, which was almost entirely solid. Phenol, C6H50H, m. p. 42, b. p. 183. Fraction III. was agitated with sodium hydroxide, filtered, neutralized with sulphuric acid and tested for phenols with ferric chloride. There was no trace of a coloration. Nor could any deep colored nitro com- pound be produced. The solution was also unaffected by bromine water. Fraction IV., 245-265, 9.53% sp. gr. .9624. 500 c.c. was redistilled and divided into four frac- tions : Fraction Range in Temp. Amt. in C. C. 1. 200 215C 79 2. 215 235C 258 3. 235 245C 54 4. 245 260C 46 Residue above ..260C 73 'Ident. of Pure Org. Comp., Mulliken, p. 200. 43 Fractions 1, 2 and 3 were cooled to 4C, the naphtha- lene pressed out while cold, purified and crystallized., Yield, 1.08%. Fraction V., 265-295, 9.16%, sp. gr. .9795. 500 c. c. was redistilled as in the preceding frao tions. Fraction Range in Temp. Amt. in C. C. 1. 200 ................... 215 15 2. 215 ................... 235 160 3. 235 ................... 245 118 4. 245 ................... 260 9:5 5. 260 ................... 295 85 .79% of naphthalene was gotten from fractions 1, 2 and 3. This makes a total yield of naphthalene from fractions II., III., IV. and V. of 3.13%. Fraction VI., 295-335, 13.38%, .9940 sp. gr. A crystalline solid settled out of fraction VI., which was of a greenish fluorescent color very unlike naph- thalene. It was thoroughly shaken up and 500 c.c. was redistilled. Amt. in C. C. 10 25 20 93 148 27 47 26 14 90 A very small amount of naphthalene separated out of fraction 1. F 1. 2. 3. 4. 5. 6. 7. 8. 9. raction 200 Range in Temp. 215C 215 . . 235C 235 245C 245 260C 260 290C 290 300C 300 320C 320 , 340C 340 360C Residue above . 360 Anthracene, CuHio, m. p. 213, b. p. 351. The greenish, fluorescent solid appeared in fractions 7, 8 and 9. These fractions were cooled in ice at oC 44 for 24 hours and filtered while cold. The crystals were pressed out, freed from oil and dried at 100, re- distilled and purified with NaOH. .1 gram was oxi- dized with chromic acid and the residue crystallized from alcohol. The melting point of the compound was found to be 279-280, which is that of anthra- quinone. 1 To further verify the test the anthraquin- o.ae was converted into oxanthranol. When anthra- cene is thus oxydised it yields anthraquinone. Yield of anthracene from fraction VI., 0.26%. Fraction VII., 235-265, 1.0342 sp. gr., 13.57%. Fraction VII. was treated as the other distillates. Fraction Range in Temp. Amt. in C. C. 1. 260 290C 100 2. 290 300C 98 3. 300 32'0C 93 4. 320 340 0l C 60 5. 340 360C 100 6. 360 365 13 Residue above 365C 36 Fractions 2, 3, 4 and 5 were cooled to 0C for 24 hours and filtered while cold. The anthracene was purified as in VI. Yield, .434%, making a total of .694% of anthracene in the tar. The amount of an- thracene oil from which it crystallized was 27.9% of the tar. Paraffins. The high boiling fractions from 240-365 when sul- phonated left a residue which was clear and oily. It was carefully washed free from sulphuric acid and the sulphonates and dried over calcium chloride. The index of refraction was found to be but slightly above that of fraction VI. of the gas oil. The sulphonation was repeated and the index of refraction lowered 45- .0115, which made it almost the same as that of the gas oil. In a discussion of the sulphonation test, Dean and Bateman 1 have this to say: "If a fraction from the distillation of creosote oil be treated under proper conditions with concentrated sulphuric acid it will be converted into a mixture of sulphonic acids, which will readily dissolve in water. If, however, there are par- affin bodies present they will not be attacked to the same degree as the aromatic hydrocarbons and when the products of the sulphonation are treated with wa- ter the paraffin compounds will remain as residual oil." Applying this test the tar seemed to show the presence of unchanged aliphatic compounds of gas oil. The following gives the results of the chemical anal- ysis in tabulated form. Water , 6.61% Ferric ferrocyanide Trace Carbon bisulphide None Thiophene Trace Benzene 22% Toluene 11% Orthoxylene Meta-xylene Para-xylene 05% Cumene Trace Phenol None Naphthalene 3.13% Anthracene oil (270-365) 27.9 % Anthracene V 65% Paraffine High % Residue 21.45% This analysis is not completed, since an effort has been made to discover the presence of only the more common aromatic hydrocarbons. The residue which remains after the six fractions of the tar have been taken is a very black tar which re- sembles "No. 24" of coal tar distillates. It is more "Circular 112, Forest Service Series. -46 brittle, however, and has a much less range of elas- ticity. It becomes very brashy at a freezing tempera- ture, and liquifies at the temperature of a warm sum- mer day. This would preclude its use as a paving material, unless mixed with coal tar. A series of experiments were conducted under the observation of the author at the Nashville Chemical Company, with mixtures of coal tar and water gas tar above 360. A very good grade of tar was pro- duced, but the tendency to separate out on the part of the unchanged paraffn gave some trouble. A high percentage of water was also found to be present, and the difficulties of distillation were greater than in coal tar. There seemed to be present a rather large quan- tity of free carbon in the form of lamp black. This lowered the utility of the tar very greatly. Neverthe- less, the increasing manufacture of water gas and the demand for a substitute for coal tar made by the pres- ent method may finally lead to the commercial utiliza- tion of water gas residue. When the process of its production has been so perfected that the residue is always uniform, and the danger of producing a high percentage of lamp black has been removed, then it will become marketable. -47 CONCLUSIONS 1. The gas oil used in the process of carburetting water gas undergoes a chemical and physical change when converted into water gas tar. 2. Some of the oil goes through the process un- changed, or nearly so, and may be detected in the dis- tillation above 250C. 3. No phenols were found in the fractions below 260C. 4. Benzene, Toluene, Xylene, Naphthalene and An- thracene were found in the tar. 5. The tar varies in density and constituency. This is governed, first, by the gas oil used in the run; sec- or.-d, by the method in which the process of water gas formation is conducted. 6. Because of a low range of flexibility and elastic- ity of the pitch the tar is not practicable as a substitute for coal tar in the preparation of paving compounds, but may be of some utility when mixed with it. 48- RETURN C.RCUIAT.ONOEFARTMENT LOAN~PERIOD HOME USE Gaylord Bros. Makers Syracuse, N. Y. PAT. JAN. 21, 1908 U.C.BERKELEY LIBRARIES 33 UNIVERSITY OF CALIFORNIA LIBRARY