ANDERSON ON THE CONSTITUTION OF X.-Ot&the Con.ditution of Anthracene or Paranaphthalira ad some of its Products of Decomposition By THolrrAs ANDERSON, M.D. F.R.S.E. Profcssor of Chemistry iu the Univcrsity of 01asg:ow. [Abstracted from the Tmnwtions of the Royal Socicty of Edinburgh,vol. xxii part iii.] THEsolid cornpounds of carbon and hydrogen 'form a class of substances to which cliemists have scarcely as yet paid that attention which their importance and interest appear to merit. With tlic exception of naphthahi very little is known regarding them and it is remarkable that the numerous and wried products of decomposition obtained from that singular substnncc sliould not have induced a morc minute examination of the kiridred com- pounds whose existence has \,cell indicated by differcut cliemists.The intcrcst ,attaching to thcsc compouiidu is all the grcatcr because according to their cliscowrcrs several of them are isomeric or at Icast polymeric with iiaplitliiiliti ; and r?. niore careful examination of them might be espectcd to throw some light on their intimate constitiitiou and tlicir relatioils to that body. No fewer than five substances said to be yolyineric with naph-tliah have been described. The arc paranuphthalin or antiwa-ceHe rnetannphthalin or retistcrene pyrene and two substances not yet nztmcd which occur together with benzene and benkopheiione among the products of the destructive distillation of benzoate of lime aid arc apparently quite distinct from one aiiotlm and the other three.All of these substances; except naphttialin have hitherto been obtained in small and some of them in very minute quantity so that. their ccnstitution has been in most instaims fixed by analysis alone ;and the difficulties atteriding the analysis of highly carbonaceous compounds at the time they were made as well as the absence of any control derived from the examination of their products of ciecomposition have naturally occasioned some doubts as to the accuracy of the formulae assigned to them. Paranaphthalin or antlirilcenc which was discovered ly Durn as ANTHRACENE OK PARANAPHTHALIN. and Laurent in the year 1832,* is the only one of these sub-stances whose examination has extended beyond the mere analysis ; and the determination of its vapour-density by the former chemist gave for it the formula C&H12 which the examination of some of its dccomposition-products by the latter was supposed to confirm.A critical examination of Laurent's experiments by no means bcars out this opinion. They are in many respects extremely imperfect were obviously rnade.on a very small quantity of mate-rial and the formulz (mostly deduced from a single analysis) are so improbable that there can be but one opinion as to the neces-sity for submitting the subject to a further investigation. Anthr:iccnc as is well known from the observatious of Dumas and Laurcnt is met with only among the latter portions of the distillation of coal-tar. It has hen little seen by chemists because hitlicrto the distillation has not generally been pushed so far as to yield it in quantity ;but during the last fcm pears thc demand for thc asphalt and the highcr oils having increascd the distillation lias been carried further aiid it has bcen found abundantly in sonic of thc products and even been used in the manufacture of macliiiiery grcilse.I have arciiled myself of the opportunity which ;Lla1ge supply afi'orcled of cxtciiditig the esaminatiori of aiithra-ccnc arid with the result of showing that its constitution diflers from that attrihutcd to it by its discoverers and that it is not ply mcric with naph thalin. Bcforc eiitcriiig 011 the details of my own experiments it mag be advisa1,lc to recapitulate shortly the history of tlic substance. As alrculy atatccl it mas discowred by Dunias arid Laurent worliiiig in coiiccrt in 1832 aiid dcscrilml by the former chemist wllo attributed to it the formula C3()H12,with which his results corrcsporitlccl very closcly.111 1835 Laurcn tt descrilicd under tlic 11;1111c ofyaru,iui,ltf/iuk.se il compound to wliicli hc giws the formixla (&1l8O4 mid lie nppcars to have regarded it as a direct product of' the action of nitl-ic acid on anthraccne. In a subse-quciit pa.pcr$ lie cxtciids his investigation in this direction and descrilm iia~f'cwcr than fivc ilifYcrciit iiitro-compounds and assigns to tlicni wry prohlemntical forniulz. In this-paper he agaiu refer3 to i';~r'"'i.2l)litli:tlesc, Init uiidcr the rinmc of antjiraceizuse giving it tllc f'orriiula C,H,O, aid stating that it is not it pro-* Allll.CI1. l'!lJS. 1 137. I.Ann. Cli. I'iiyj. Ix. 2%. $ Thill. Ixxii. 415. ANDERSON ON THE CONSTITUTION OF duct of the direct action of nitric acid on antbracene but formed by the decomposition of a nitro-compound in a manner precisely similar to that in which naphthase is obtained from nitronaph-thalin. He mentions that a substance of similar properties is obtained from several of the nitro-compounds he prepared but leaves it an open question whether it is in all cases the same or whether it differs in constitution according to the nitro-compound from which it is produced. He also describes a chlorine substitu- tion-product and adopts the name of aathracene-a change even then advisable and which the results of my investigation show to be quite indispensable Crude anthracene is in the form of a soft yellow mass not unlike palm oil but with a greenish tinge and harder consistence; in this state it contains a little naphthalin and a considerable quantity of oil of high boiling point which 'causes it to leave a greasy stain on paper and to melt easily when rubbed between the fingers.It has a decided though not strong smell due partly to the naphthaiin but still more to the oil with which it is con-. taminated aid which it loses ou purification. It is soluble though not abundantly in alcohol but dissolves with tolerable facility in ether turpentine and still better in benzole. Methy-lated spirit was in the first instance used for its purification.The first solution on cooling deposited thick oily globules with a small quantity of crystals ;but after several successive quantities of apirit had been used crystals were deposited free from oil but still retaining the yellow colour of the original substance and- apparently owing to the removal of the oil-were much less soluble in new quantities of spirit. By repeated crystallisations it was found possible to obtain t'he anthracene quite colourless ; but the process was too tedious to be employed for preparing it on the larger scale. Other solvents and more particularly benzole were likewise tried ; but though preferable the complete removal of the colouring matter is difficult with them also and it was found necessary to begin by distilling the crude substance in a small iron still.The first portions which passed over during the process contained much naphthalin and oil but were quite free from colour. As the distillation proceeded however the colour gradually increased and at the end a small quantity of' a dark green substance remained in the retort. The first portions of the distillate were pressed to remove the oil and the last portions redistilled so as to get rid of thc colour as completely as possible ANTHBACENE OB PABANAPETHALIN. and the purification finished by repcated crystallisation from benzole and sometimes by sublimation. Antliracene is depositcd from its solution in perfectly colourlesa scales gencrally of very small size even when large solutions have been allowed to cool.Those obtained from spirit are generally the best and wheo suspended in the solution have a fine satiny lustre which they lose to some cxtent when dried. From benzole the crystais are somewhat granular and less brilliant in appear- ance. By sublimation it is obtained in thin plates resembling those of naphthalin but smaller and of inferior lustre. When quite pure it has no smell but it is apt to retain a trace of oil which communicates to it a faint ernpyreumatic odour. It ie entirely devoid of taste It is not volatile at ordinary tempera- tures but is slowly volatilised in the water-bath. At higher tem- peratures it sublinies freely. It melts at 416" F. into a trapspa- rent colourless liquid which on cooling solidifies into a foliated crystalline mass and aic a higher temperature distils unchanged.It is insoluble in water sparingly soluble in alcohol but more so in ether benzole and the volatile oils. The alkalies are without action upon it but sulphuric acid dissolves it and acquires a green colour with formation of a sulpho-acid; and nitric\ acid even when moderately dilute acts rapidly upon it. Chlorine and bromine form substitution-products. The analysis of anthracene at ' first prcscnted some difficulties. When oxide of copper was employed in the usual way the carbon was always deficient while chromate of lead gave an accurate result with that element but a marked excess on the hydrogen.* Oxide of copper and clilorate of potash were therefore resorted to and with success.The results correspond exactly with the formiila C,,H,,. This is precisely the constitution of a substance described some years since by Fri t zsch et as a new carlm-hydrogen obtaiiictl from coal-tar with which also its properties closcly agree. A careful comparison of the two substances made by Professor Fritz sclie arid myself during I have had freqlient occafiion to obAerVe that in the analjsia of carbo-hydrogene with chron~:~te of Ic.id a considerable CXCPSH of hydrogen is oftcn olitnined. I at first attributed this to impurities in the chromate btit analyees made with a pure material ~peciallymade for the piirpo~e,showed the game cxcees. I have not examined into the cause of ttik phenomenon. t J. pr. Chern. Ixxiii. 282.ANDERBON ON THE CONSTITUTION OF I) visit b paid to Glaagow some time since satisfied us that hi8 substance really ie anthracene. The picric acid compounds of the two are completely identical and have 8 fine ruby-red colour which distinguishes the compounds in question from those ob-tained from the other carbo-hydrogens. An analysis of the com- pound obtained from anthracene gave the formula C&HIO.CJX (NO,),O, which is that given by Fritzsche for his compound. ACTION ACIDON ANTlIRACENE. OF NITRIC Anthracene is but little acted on by cold nitric acid hut the boiling acid even when moderately dilute attacks it with con-sideFable rapidity the products depending upon the strength of the acid and the length of time during which the action is continued.Vxantlrracene C,,H,O,.-When anthracene is boiled for some day8 with nitric acid of sp. gr. 1.2,red fumes are evolved and a resinova mass is obtained which becomes hard and gritty ou cool-ing. The same change may be more rapidly effected with acid of ap. gr. 1*4 but the product is then liable to be contaminated with aome other compounds. The substance was washed with water and purified by crystallisation from alcohol or bexizole. It is theu obtained in crystals which when deposited from alcohol are long silky needles but from benzole are shorter and more compact. They are of a light buff colour and have neither taste nor smell ; they are insoluble in water sparingly soluble in alcohol and more so in benzole. They arc completely soluble in boilirig nitric acid of sp.gr. 1.4,and are deposited unchanged on cooling. Concen-trate& sulphuric acid in the cold dissolves them with orange colour which becomes deep red on heating and on dilution with watcr the oxanthraccne is deposited unchanged. Oxanthrwenc aiiblimcs when heated and is deposited unaltered in fine needles of conei-derable length. It may be distilled without decomposition over quick-lime. Its volatility may be taken advantage of as a mcans of preparing it as it is only necessary to boil anthracene in a retort with nitric acid and to continue the heat until the acid has distilled over and the oxnntliracene sublimes any other compounds formed at the same time hcing decomposed. Oxanthracene is derived from arithraccne by tlie removal of -two equivalents of h$lrogeii and tlie addition of four of oxygen.It belongs to a class of substaiiccs of which thcre are very few ANTHRACENE OB PABANAPATHALIN. examples and for which we have no satisfactory system of nomen-clature. I have given it the provisional name of oxanthracene as recalling its mode of formation. Binitr0xanthracene.-Whe6 anthracene mas boiled for a long time with nitric acid with occasional addition of -fuming acid red fumes continued to be given off and a resinous eubstance waa gradually produced. The substance was washed with water and dried. It appeared to be a mixture of some of the laat substance with R new compound which was obtained by heating it wiih a small quantity of alcohol aud cooling.It is deposited as a red powder which shows but little disposition to crystalbe. Analysb gave results affording a distant approximation to the formula C,,H6 (N0J204, which probably represents its constitution ;but as itu properties showed nothing of interest I did not prosecute its purification further. Anthracenic Acid.-When the nitric acid and the washingsof the preceding compound are carefully evaporated over the water- bath a pellow crystalline acid is obtained. It is very soluble ir water arid gives crystallisable salts with ammonia and potash and precipitates the salts of lead and baryta. The further invest@ tion of this substance is reseired for a future communication. ACTION ON ANTHRACENE. OF BROMINE Bromine acts rather slowly upon anthracene in the cold.The two substances when mixed together concrete into a resinous- looking mass the interior of which is not comp!etely siturated with bromine and it was found most convenient to expose the aiithracene in a thin layer under a bell glass along with a capsule containing bromine. After a day or two’s exposure the anthracene agglutinates into a mass which must be removed reduced to powder and reintroduced ; and this treatment is repeated as long as bromine is absorbed. This mass which has a brown colour dissolves in benzole and on cooling deposits hexbromide of anthracene in crys-tals which are purified by solution in benzole or ether. It is thus obtained in small hard white granular crystals apparently rhom- boidal. They are sparingly soluble in alcohol ether and benzole.Nitric acid acts upon them but slightly. When heated with strong sulphuric acid they fuse and bromine and hydrobromic acid are expelled. On digestion with alcoholic potash they imme- diately becoinc ycllow and arc converted into another compound. ANDEBBOX ON THE CONBTITUTIOI OF When heated to 348' F. they become brown and at 3610 fuse and give off bromine. Analysis gave the results &peeing nearly with the formula C,,H,,Br6. The substance is produced hy the direct absorption of six equivalents of bromine. Tetrdrominated Anthracene.-When the preceding compound is treated with an alcoholic solution of potash it swells up con-siderably and acquires a bright sulphur-yellow colour the solutiou containing bromide of potassium.This change occurs in the cold but it is more couvenient to heat the solution. The yellow powder is collected on a filter wmhed dried and crystallized from boiling benzole; It is thus obtained in long yellow needleu having a fine silky lustre. It is very sparingly soluble in cold alcohol ether and beuzole-more so when hot. Boiling benzole is its best solvent but evem of this it requires above a hundred times its weight. It melts at 460" F. and gives a dark-coloured mass which has undergone partial decomposition. The portions used for analysis were crystallieed from benzole and then washed with ether. Analysis gives for the constitution of the compound C2RHSBr4 a somewhat unusual formula differing from that of most similar compounds.In general when a bromide or chloride of an organic compound is treated with potash one half of the haloid is removed in combination with hydrogen the remainder passing into the radical. In this case howcver only two equivalcnts of hydrogen are removed and the formula of the cpmpouiicl ought in all pro- bability to be written C28€1813r2. Br,. ACTION ON ANTHRACEXE. OF CIILORINE The examination of thc compounds produced by the action of chlorine on anthracene is attended with some difficulty the changes occurring being of a somewhat complicated kind ; more than one substance being gcncrally obtained and thc nature and proporbion of the products depending very greatly on the circumstances of the experinleiit. Chlorine is rcatlily absorbed by anthracene in the cold and if the current is rapid it becomes warm gives off hydro-chloric acid in abundance atid is cventually converted into a hard cake.If the clilorine be passed through it in a slow current the evolution of hydrochloric acid is greatly diminished although it cannot he altogether avoided; and when this is done and the stream of chlorine is not continued too long the principal product is ANTHBACENE OR PABANAPRTHALIN. Bichloride of qnthracene C,,H,oCl,.-The mass obtained by the action of chlorine dissolves readily in benzole and on cooling groups of radiating needles often of considerable length are depo- sited. The bichloride is readily soluble in alcohol but only very sparingly in ether.When crystallised from alcohol it is very liable to lose hydrochloric acid and this change always takes place to some extent which causes a slight excess of carbon and defi-ciency of chlorine in the analysis. Chloranthracene C,,H&l.-W hen anthracene is treated with a rapid current of chlorine continued for a short time only this compound is produced. Jt may also be obtained by decomposing the preceding substance with alcoholic potash. It is soluble in alcohol ether and benzole from the last of which solutions it ie deposited in small hard scaly crystals When chlorine is passed over anthracene kept hot it is absorbed in much larger quantity and hydrochloric acid is abundantly evolved. The compounds thus obtained depend entirely on the length of time during which the current is continued and products analysed at different periods were found to contain very different quantities of carbon an6 chlorine; and as the substances produced differ little in solubility it was found difficult to effect their sepa- ration.When the passage of chlorine is continued for about eight days the product is semisolid and the greater part dissolves easily in cold ether ; and when this solution is evaporated first an oily chloride and then crystals are deposited. The crystals are soluble in benzole alcohol and ether and were found to have a composition agreeing with the somewhat improbable formula C,,H,Cl ; but it is-quite possible that the substance may be a mixture. The oi!y chloride gives more than one crystalline substance when treated with alcoholic potash.The facts now detailed are sufficient to fix the constitution of mthracene and to show that its chemical relations are of con& derable interest. Its formula connects it,with certain substances derived from oil of bitter almonds and more especially with stilbece the carbo-hydrogen discovered by Laurent from which it differs by two equivalents of hydrogen. A similar relation exists between oxanthracene and benzil as is seen by the following corn-parison of their formulae :-Anthracene . . C-8H,o Stilbene . . . CPHIZ Oxanthracene . . CL8H,04 iI Benzil . . . . CzeHloOc