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COALITION (Lat. coalitio, the verbal ...
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See also:COALITION (See also:Lat. coalitio, the verbal substantive of coalescere, to grow together) , a See also:combination of bodies or parts into one See also:Modern conditions. See also:body or whole. The word is used, especially in a See also:political sense, of an See also:alliance or temporary See also:union for See also:joint See also:action of various See also:powers or states, such as the coalition of the See also:European powers against See also:France, during the See also:wars of the See also:French Revolution; and also of the union in a single See also:government of distinct parties or members of distinct parties. Of the various coalition ministries in See also:English See also:history, those of See also:Fox and See also:North in 1782, of the Whigs and the Peelites, under See also:Lord See also:Aberdeen in 1852-1853, and of the Liberal Unionists and Conservatives in Lord See also:Salisbury's third See also:ministry in 1895, may be instanced. See also:COAL-See also:TAR, the See also:black, viscous, sometimes semi-solid, fluid of See also:peculiar See also:smell, which is condensed together with aqueous " See also:gas liquor " when the volatile products of the destructive See also:distillation of coal are cooled down. It is also called " gas-tar," because it was formerly exclusively, and even now is mostly, obtained as a by-product in the manufacture of coal-gas, but the tar obtained from the modern See also:coke-ovens, although not entirely identical with gas-tar, resembles it to such an extent that it is worked up with the latter, without making any distinction in practice between the two kinds. Some descriptions of gas-tar indeed differ very much more than coke-See also:oven tar from pure coal-tar, viz. those which are formed when bituminous shale or other materials, considerably deviating in their nature from coal, are mixed with the latter for the purpose of obtaining gas of higher See also:illuminating See also:power. It may be generally said that for the purpose of tar-distillers the tar is all the more valuable the less other materials than real coal have been used by the gas-maker. All these materialsbog-See also:head shale, bituminous See also:lignite and so forth—by destructive distillation yield more or less paraffinoid See also:oils, which render the See also:purification of the benzols very difficult and sometimes nearly impossible for the purposes of the manufacturer of coal-tar See also:colours. Neither too high nor too See also:low a temperature should have been observed in gas-making in See also:order to obtain a See also:good quality of tar. Since in See also:recent times most gas retorts have been provided with See also:heating arrangements based on the See also:production of gaseous See also:fuel from coke, which produce higher temperatures than See also:direct firing and have proved a See also:great See also:economy in the See also:process of gas-making itself, the tar has become of decidedly inferior quality for the purposes of the tar-distillers, and in particular yields much less benzol than formerly. Entirely different from gas-tar is the tar obtained as a by-product from those (Scottish) blast furnaces which are worked with splint-coal. This tar contains very little aromatic hydro-carbons, and the phenols are of quite a different See also:character from those obtained in the working of gas-tar. The same holds good of oil-gas tars and similar substances. These should not be worked up like gas-tars. The See also:ordinary yield of tar in the manufacture of coal-gas is between 4 and 5% of the See also:weight of the coal. Rather more is obtained when passing the gas through the apparatus of E. See also:Pelouze and P. See also:Audouin, where it is exposed to several shocks against solid surfaces, or by carrying on the process at the lowest possible temperature, as proposed by H. J. See also:Davis, but this " carbonizing process " can only pay under See also:special circumstances, and is probably no longer in See also:practical use. All coal-tars have a specific gravity above that of See also:water, in most cases between 1.12 and 1.20, but exceptionally up to 1.25. The heavier tars contain less benzol than the lighter tars, and more " fixed See also:carbon," which remains behind when the tars are exhausted of benzol and is a decidedly objectionable constituent. All tars also mechanically retain a certain quantity of water (or rather gas-liquor), say, 4% on the See also:average, which is very See also:obnoxious during the process of distillation, as it leads to " bumping," and therefore ought to be previously removed by prolonged settling, preferably at a slightly elevated temperature, which makes the tar more fluid. The water then rises to the See also:top, and is removed in the ordinary way or by special " separators." The tar itself is a mixture of exceedingly complex character. The great bulk of its constituents belongs to the class of " aromatic " See also:hydrocarbons, of very different See also:composition and degreesof volatility, beginning with the simplest and most volatile, See also:benzene (See also:Celle), and ending with an entirely indistinguishable See also:mass of non-volatile bodies, which compose the See also:pitch See also:left behind in the tar-stills. The hydrocarbons mostly belong to the benzene See also:series C„H2,a_8, the See also:naphthalene series CnH2n_12, and the See also:anthracene and phenanthrene series C,,H2n_18. Small quantities of " fatty " (" aliphatic ") hydrocarbons are never absent, even in pure tars, and are found in considerable quantities when shales and similar matters have been mixed with the coal in the gas-retorts. They belong mostly to the paraffins C„H2n+2, and the olefines CnH2n. The " See also:asphalt " or soluble See also:part of the pitch is also a mixture of hydrocarbons, of the See also:formula C„H2n; even the " carbon," left behind after treating the pitch with all possible solvents is never pure carbon, but contains a certain quantity of See also:hydrogen, although less than any of the volatile and soluble constituents of the tar. Besides the hydrocarbons, coal-tar contains about 2% of the simpler phenols C„H2,,_7OH, the best known and most valuable of which is the first of the series, carbolic See also:acid (q.v.) C6H5OH, besides another interesting oxygenized substance, cumarone C8H60. The phenols, especially the carbolic acid, are among the more valuable constituents of coal-tar. Numerous See also:sulphur compounds also occur in coal-tar, some of which impart to it their peculiar nauseous smell, but they are of no technical importance or value. Still more numerous are the nitrogenated compounds contained in coal-tar. Most of these are of a basic character, and belong to the See also:pyridine and the See also:quinoline series. Among these we find a somewhat considerable quantity of See also:aniline, which, however, is never obtained from the tar for commercial purposes, as its See also:isolation in the pure See also:state is too difficult. The pyridines are now mostly recovered from coal-tar, but only in the shape of a mixture of all members of the series which is principally employed for denaturing See also:alcohol. Some of these nitrogenated compounds possess considerable antiseptic properties, but on the whole they are only considered as a contamination of the tar-oils.
Applications of Coal-Tar in the Crude State.—Large quantities of coal-tar are employed for various purposes without submitting it to the process of distillation. It is mostly advisable to de-See also:hydrate the tar as much as possible for any one of its applications, and in some cases it is previously boiled in order to remove its more volatile constituents.
No preparation whatever is needed if the tar is to be used as fuel, either for heating the gas-retorts or for other purposes. Its heating-value is equal to the same weight of best coal, but it is very difficult to See also:burn it completely without producing a great See also:deal of evil-smelling See also:smoke. This See also:drawback has been overcome by employing the same means as have been found suitable for the See also:combustion of the heavy See also:petroleum residues, called " masut," viz. converting the tar into a See also:fine spray by means of See also:steam or compressed See also:air. When the gas-maker cannot conveniently or profitably dispose of his tar for other purposes, he See also:burns it by the above means under his retorts.
Several processes have also been patented for producing illuminating gas from tar, the most notable of which is the Dinsmore process. This process has been adversely criticized by very competent gas-makers, and no great success can be expected in this See also:line.
Coal-tar is very much employed for See also:painting See also:wood, See also:iron, See also:brick-See also:work, or See also: Coal-tar should not be used for tarring the woodwork and See also:ropes of See also:ships, a purpose for which only wood-tar has been found suitable. One of the most considerable outlets for crude tar is in the manufacture of roofing See also:felt. This See also:industry was introduced in See also:Germany upwards of a See also:hundred years ago, even before coal-tar was available, and has reached a very large See also:extension both in that See also:country and in the See also:United States, where most of the gas-tar seems to be devoted to this purpose. In the United See also:Kingdom it is much less extensive. For this manufacture a special fabric is made from pure woollen fibre, on rolls of about 3 ft. width and of considerable length. The tar must be previously dehydrated, and is preferably deprived of its more volatile portions by heating in a still. It is heated in an iron See also:pan to about 900 or Too° C.; the fabric is See also:drawn through it by means of rollers which at the same See also:time squeeze out the excess of tar; on coming out of these, the tarred felt is covered with a layer of See also:sand on both sides by means of a self-acting apparatus; and is ultimately See also:wound See also:round wooden rolls, in which state it is sent out into the See also:trade. This roofing-felt is used as a cheap covering, both by itself and as a grounding for tiles or slates. In the former See also:case it must be kept in repair by repainting with tar from time to time, a top covering of sand or small See also:gravel being put on after every coat of paint. Coal-tar is also employed for the manufacture of See also:lamp-black. This is done by burning the tar in ovens, connected with brick-See also:chambers in which the large quantity of See also:soot, formed in this process, deposits before the gases See also:escape through the See also:chimney. Numerous See also:patents have been taken out for more efficiently See also:collecting this soot. Most of it is employed without further manipulation for the manufacture of electric carbons, See also:printing inks, See also:shoe-blacking, patent See also:leather and so forth. A finer quality of lamp-black, See also:free from oily and empyreumatic parts, is obtained by calcining the soot in closed iron pots at a red See also:heat.
Distillation of Coal-Tar.—Much more important than all applications of crude coal-tar is the industry of separating its constituents from it in a more or less pure See also:form by fractional distillation, mostly followed by purifying processes. Most naturally this industry took its rise in Great See also:Britain, where coal-gas was invented and made on a large See also:scale before any other nation took it up, and up to this See also:day both the manufacture of coal-gas and the distillation of the tar, obtained as a by-product thereof, are carried out on a See also: See also: The last of the great discoveries in that line was the preparation of alizarine from anthracene by C. Graebe and C. T. See also:Liebermann, in 1868, soon followed by patents for its practical manufacture by Sir W. H. Perkin in See also:England, and by Graebe, Liebermann and H. See also:Caro in Germany. The present extension of the industry of coal-tar distilling can be only very roughly estimated from the quantity of coal-tar produced in various countries. Decidedly at the head is Great Britain, where about 700,000 tons are produced per annum, most of which probably finds its way into the tar-distilleries, whilst in Germany and the United States much less gas-tar is produced and a very large proportion of it is used for roofing-felt and other purposes. We shall now give an outline of the processes used in the distillation of tar. Dehydration.—The first operation in coal-tar distilling is the removal of the mechanically enclosed water. Some water is chemically combined with the bases, phenols, &e., and this, of course, cannot be removed by See also:mechanical means, but splits off only during the distillation itself, when a certain temperature has been reached. The water mechanically present in the tar is separated by long repose in large reservoirs. Very thick viscous tars are best mixed with thinner tars, and the whole is gently heated by coils of pipes through which the heated water from the oil-condensers is made to flow. Sometimes special " tar-separators " are employed, working on the centrifugal principle. The water rises to the top and is worked up like ordinary gas-liquor. More water is again separated during the heating-up of the tar in the still itself, and can be removed there by a special overflow. Tar-Stills.—The tar is now pumped into the tar-still, fig. T. This is usually, as shown, an upright wrought-iron See also:cylinder, with an arched top, and with a bottom equally vaulted upwards for the purpose of increasing the heating See also:surface and of raising the level of the pitch remaining at the end of the operation above the See also:fire-flues. The fuel is consumed on the fire-See also:grate a, and, after having traversed the holes bb in the See also:annular See also:wall e built below the still, the See also:furnace gases are led around the still by means of the flue d, whence they pass to the chimney. See also:Cast-iron necks are provided in the top for the outlet of the vapours, for a See also:man-hole, See also:supply-See also:pipe, thermometer-pipe, safety See also:valve, and for air and steam-pipes reaching down to the bottom and branching out into a number of distributing ' The illustrations in this See also:article are from Prof. G. See also:Lunge's Coal arms. Near the top there is an overflow pipe which comes into action on filling the still. In the lowest part of the bottom there is a See also:running-off valve or tap. In some cases (but only exceptionally) a perpendicular See also:shaft is provided, with See also:horizontal arms, and chains See also:hanging down from these See also:drag along the bottom for the purpose of keeping it clean and of facilitating the escape of the vapours. This arrangement is quite unnecessary where the removal of the vapours is promoted by the injection of steam, but this steam must be care-fully dried beforehand, or, better, slightly superheated, in order to prevent explosions, which might be caused by the entry of liquid water into the tar during the later stages of the work, when the temperature has arisen far above the boiling-point of water. The steam acts both by stirring up the tar and by rapidly carrying off the vapours formed in distillation. The latter object is even more thoroughly attained by the application of a vacuum, especially during the later See also:stage of distillation. For this purpose the receivers, in which the liquids condensed in the cooler are collected, are connected with an air See also:pump or an ejector, by which a vacuum of about 4 in., say } See also:atmosphere, is made which lowers the boiling process by about 80° C.; this not merely hastens the process, but also produces an improvement of the quality and yield of the products, especially of the anthracene, and, moreover, lessens or altogether prevents the formation of coke on the still-bottom, which is otherwise very troublesome. Most manufacturers emply ordinary stills as described. A few of them have introduced continuously acting stills, of which that constructed 'by See also:Frederic Lennard has probably found a wider application than any of the others. They all work on the principle of gradually heating the tar in several compartments, following one after the other. The fresh tar is run in at one end and the pitch is run out from the other. The vapours formed in the various compartments are separately carried away and condensed, yielding at one and the same time those products which are obtained in the ordinary stills at the different periods of the distillation. Although in theory this continuous process has great advantages over the ordinary See also:style of working, the complication of the apparatus and practical difficulties arising in the manipulation have deterred most manufacturers from introducing it. The tar-stills are set in See also:brickwork in such a manner that there is no over-heating of their contents. For this purpose the fire-grate is placed at a good distance from the bottom or even covered by a brick See also:arch so that the See also:flame does not See also:touch the still-bottom at all and acts only indirectly, but the sides of the still are always directly heated. The fire-flue must not be carried up to a greater height than is necessary to provide against the overheating of any part of the still not protected inside by liquid tar, or, at,the end of the operation, by liquid pitch. The outlet pipe is equally protected against overheating and also against any stoppage by pitch solidifying therein. The capacity of tar-stills ranges from 5 to 5o tons. They hold usually about 10 tons, in which case they can be worked off during one day. The vapours coming from the still are condensed in coolers of various shapes, one of which is shown in See also:figs. 2 and 3. The cooling-pipes are best made of cast-iron, say 4 in. wide inside and laid so as to have a continuous fall towards the bottom. A steam-pipe (b) is provided for heating the cooling water, which is necessary during the later part ,of the operation to prevent the stopping up of the pipes by the solidification of the distillates. A See also:cock (a) allows steam to be injected into the condensing See also:worm in order to clear any obstruction. The cooling-pipe is at its See also:lower end connected with receivers for the various distillates in such a manner that by the turning of a cock the flow of the distillates into the receivers can be changed at will. In a suitable place See also:provision is made for watching the colour, the specific gravity, and the general appearance of the distillates. At the end of the See also:train of apparatus, and behind the vacuum pump or ejector, when one is provided, there is sometimes a purifier for the gases which remain after condensation; or these gases are carried back into the fire, in which case a water-See also:trap must be inter-posed to prevent explosions. Distillation of the Tar.—The number of fractions taken during the distillation varies from four to six. Sometimes a first fraction is taken as " first runnings," up to a temperature of 105° C. in the still,and a second fraction as " light oil," up to 210° C., but more usually these two are not separated in the first distillation, and the first or " light oil " fraction then embraces everything which comes over until the drops no longer See also:float on, but show the same specific gravity as water. The specific gravity of this fraction varies from 0.91 to 0.94. 'The next fraction is the " See also:middle oil " or " carbolic oil," of specific gravity I•ot, boiling up to 240° C.; it contains most of the carbolic acid and naphthalene. The next fraction is the " heavy oil " or " creosote oil," of specific gravity 1.04. Where the nature of the coals distilled for as is such that the tar contains too little anthracene to be economically recovered, the creosote-oil fraction is carried right to the end; but otherwise, that is in most cases, a last fraction is made at about the temperature 270° C., above which the "anthracene oil " or " See also:green oil " is obtained up to the finish of the distillation. During the light-oil See also:period the firing must be performed very cautiously, especially where the water has not been well removed, to prevent bumping and boiling over. It has been observed that, apart from the water, those tars incline most to boiling over which contain an unusual quantity of " fixed carbon." During this period See also:cold water must be kept running through the cooler. The distillate at once separates into water (gas-liquor) and light oil, floating at the top. Towards the end of this fraction the distillation seems to cease, in spite of increasing the fires, and a rattling See also:noise is heard in the still. This is caused by the combined water splitting off from the bases and phenols and causing slight explosions in the tar. As soon as the specific gravity approaches I•o, the supply of cold water to the cooler is at least partly cut off, so that the temperature of the water rises up to 40° C. This is necessary because otherwise some naphthalene would crystallize out and plug up the pipes. If a little steam is injected into the still during this period no stoppage of the pipes need be feared in any case, but this must be done cautiously. When the carbolic oil has passed over and the temperature in the still has risen to about 240° C., the distillate can be run freely by always keeping the temperature in the cooler at least up to 4o C. The " creosote oil " which now comes over often separates a good deal of solid naphthalene on cooling. The last fraction is made, either when the thermometer indicates 2700 C., or when " green grease " appears in the distillate, or simply by judging from the quantity of the distillate. What comes over now is the " anthracene oil." The firing may cease towards the end as the steam (with the vacuum) will finish the work by itself. The water in the cooler should now approach the boiling-point. The point of See also:finishing the distillation is different in various places and for various See also:objects. It depends upon the fact whether soft or hard pitch is wanted. The latter must be made where it has to be sold at a distance, as soft pitch cannot be easily carried during the warmer See also:season in railway trucks and not at all in ships, where it would run into a single lump. Hard pitch is also always made where as much anthracene as possible is to be obtained. For hard pitch the distillation is carried on as far as practicable without causing the See also:residue in the still to " coke." The end cannot be judged by the thermometer, but by the appearance and quantity of the distillate and its specific gravity. If carried too far, not merely is coke formed, but the pitch is porous and almost useless, and the anthracene oil is contaminated with high-boiling hydrocarbons which may render it almost worthless as well. Hard pitch proper should soften at loo° C., or little above. Where the distillation is to stop at soft pitch it is, of course, not carried up to the same point, but wherever the pitch can be disposed of during the colder season or without a long See also:carriage, even the hard pitch is preferably softened within the still by pumping back a sufficient quantity of heavy oil, previously deprived of anthracene. This makes it much easier to See also:discharge the still. When the contents consist of soft pitch they are run off without much trouble, but hard pitch not merely emits extremely pungent vapours, but is mostly at so high a temperature that it takes fire in the air. Hard pitch must, therefore, always be run into an iron or brick cooler where it cools down out of contact with air, until it can be drawn out into the open pots where its solidification is completed. Most of the pitch is used for the manufacture of " briquettes " (" patent fuel "), for which purpose it should soften between 550 and 8o° C. according to the requirements of the buyer. In Germany upwards of 50,000 tons are used annually in that industry; much of it is imported from the United Kingdom, whence also France and See also:Belgium are provided. Apart from the softening point the pitch is all the more valued the more constituents it contains which are soluble in See also:xylene. The portion insoluble in this is denoted as " fixed carbon." If the See also:briquette manufacturer has bought the pitch in the hard state he must himself bring it down to the proper softening point by re-melting it with heavy coal-tar oils.
We now come to the treatment of the various fractions obtained from the tar-stills. These operations are frequently not carried out at the smaller tar-works, which sell their oils in the crude state to the larger tar-distillers.
Working up of the Light-Oil Fraction.—The greatest portion of the light-oil fraction consists of aromatic hydrocarbons, about one-fifth being naphthalene, four-fifths benzene and its homologues, in the proportion of about too benzene, 30 See also:toluene, 15 xylenes, lo trimethylbenzenes, I tetramethylbenzene. Besides these the light-oil contains 5–15% phenols, 1–3% bases, 0.1 sulphuretted compounds, 0.2–0.3% nitriles, &c. It is usually first submitted to a preliminary distillation in directly fired stills, similar to the tar-stills, but with a dephlegmating head. Here we obtain (I) first runnings (up to 0.89 spec. See also: After this the crude benzol is thoroughly washed with water and dilute caustic soda solution, until its reaction is neutral. The mixing of the basic, acid and aqueous washing-liquids with the oils is performed by compressed air, or more suitably by mechanical stirrers, arranged on a perpendicular, or better, a horizontal shaft. Precisely the same treatment takes place with the next fraction, the " heavy benzols," and the oils left behind after the washing operations now go to the steam-stills. The heaviest hydrocarbons are sometimes twice subjected to the operation of washing. The washed crude benzols are now further fractionated by distillation with steam. The steam-stills are in nearly all details on the principle of the " See also:column apparatus " employed in the distillation of alcoholic liquids, as represented in fig. 4. They are usually made of cast iron. The still itself is either an upright or a horizontal cylinder, heated by a steam-coil, of a capacity of from moo to 2000 gallons. The superposed columns contain from 20 to 50 compartments of a width of 22 or 3 ft. The vapours pass into a cooler, and from this the distillate runs through an apparatus, where the liquor can be seen and tested, into the receivers. The latter are so arranged that the water passing over at the same time is automatically re-moved. This is especially necessary, because the last fraction is distilled by means of pure steam. The fractions made in the steam distillation vary at different works. In some places the pure hydrocarbons are See also:net extracted and here only the articles called : " 90 per cent. benzol," " 5o per cent. benzol," " solvent naphtha," " burning naphtha " are made, or any other commercial articles as they are ordered. The expression " per cent." in this case does not signify the percentage of real benzene, but that portion which distils over up to the temperature of too° C., when a certain quantity of the article is heated in See also:glass retorts of adefinite shape, with the thermometer inserted in the liquid itself. By the application of well-constructed rectifying-columns and with proper care it is, however, possible to obtain in this operation nearly pure benzene, toluene, xylene, and cumene (in the two last cases a mixture of the various isomeric hydrocarbons). These hydrocarbons contain only a slight proportion of thiophene and its isomers, which can be removed only by a treatment with fuming sulphuric acid, but this is only exceptionally done. Sometimes the pyridine bases are recovered from the tarry acid which is obtained in the treatment of the light oil with sulphuric acid, and which contains from lo to 30 % of bases, chiefly pyridine and its homologues with a little aniline, together with resinous substances. The latter are best removed by a partial precipitation with ammonia, either in the shape of gas or of concentrated ammoniacal liquor. This reagent is added until the acid reaction has just disappeared and a faint smell of pyridine is perceived. The mixture is allowed to See also:settle, and it then separates into two layers. The upper layer, containing the impurities, is run off; the lower layer, containing the sulphates of ammonia and of the pyridine bases, is treated with ammonia in excess, where it separates into a lower aqueous layer of ammonium sulphate solution and an oil, consisting of crude pyridine. This is purified by fractionation in iron stills and distillation over caustic soda. Most of it is used for denaturing spirit of See also:wine in Germany, for which purpose it is required to contain 90% of bases boiling up to 140° C. (see ALCOHOL).
Working up of the Middle-Oil Fraction (Carbolic Oil Fraction).—Owing to its great percentage of naphthalene (about 40%) this fraction is solid or semi-solid at ordinary temperatures. Its specific gravity is about 1.2; its colour may vary from light yellow to dark See also: It is at the ordinary temperature a semi-solid mixture of about 20 % crystallized hydrocarbons (chiefly naphthalene), and 8o% of a dark brown, nauseous smelling oil, of 1.04 spec. gray., and boiling between Zoo° and 300° C. The liquid portion contains phenols, bases, and a great number of hydrocarbons. Sometimes it is redistilled, when most of the naphthalene passes over in the first fraction, between 18o° and 230° C., and crystallizes out in a nearly pure state. The oily portion remaining behind, about 60 % of this distillate, contains about 36% phenols and 3 % bases. It has highly disinfectant properties and is frequently converted into special See also:disinfectants, e.g. by mixing it with four times its See also:volume of slaked See also:lime, which yields " disinfectant See also:powder " for stables, railway cars, &c. Mixtures of potash soaps (soft soaps) with this oil have the See also:property of yielding with water emulsions which do not settle for a long time and are found in the trade as " creolin," " sapocarbol," " lysol," &c. That description of creosote oil which is sold for the purpose of pickling railway sleepers, See also:telegraph posts, timber for the erection of wharves and so forth, must satisfy special requirements which are laid down in the specifications for tenders to public bodies. These vary to a considerable extent. They always stipulate (I) a certain specific gravity (e.g. not below 1.035 and not above 1.065); (2) Certain limits of boiling points (e.g. to yield at most 3% up to 150°, at most 30 % between 15o° and 255°, and at least 85 % between 150° and 355°) ; (3) a certain percentage of phenols, as shown by extraction with caustic soda solution, say 8 to to %. Much of this creosote oil is obtained by mixing that which has resulted in the direct distillation of the tar with the liquid portion of the anthracene oils after separating the crude anthracene (see below). It is frequently stipulated that the oil should remain clear at the ordinary temperature, say 15° C., which means that no naphthalene should crystallize out. Working up the Anthracene Oil Fraction.—The crude oil boils between 28o° and 400° C. It is liquid at 6o° C., but on cooling about 6 to ro% of crude anthracene separates as greenish-yellow, sandy crystals, containing about 3o% of real anthracene, together with a large percentage of See also:carbazol and phenanthrene. This See also:crystallization takes about a See also:week. The crude anthracene is separated from the mother oils by See also:filter presses, followed by centrifugals or by hot See also:hydraulic presses. The liquid oils are redistilled, in order to obtain more anthracene, and the last oils go back to the creosote oil, or are employed for softening the hard pitch (vide supra). The crude anthracene is brought up to 50 or 6o, sometimes to 8o %, by washing with solvent naphtha, or more efficiently with the higher boiling portion of the pyridine bases. The naphtha removes mostly only the phenanthrene, but the carbazol can be removed only by pyridine, or by sub-liming or distilling the anthracene over caustic potash. The whole of the anthracene is sold for the manufacture of artificial alizarine. Steinkohlentheer," Kraemer and Spreker, in Encyklopadisches Handbuch der technischen Chemie (4th ed., 1905, viii. I). (G. Additional information and CommentsThere are no comments yet for this article.
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