24 



ANILINE, OR COAL-TAR COLORS. 



by Hofmann, and tlie products of the reaction 

 were very complex, the examination was at the 

 time discontinued. But practical men seized 

 and acted on the hint; and M. Verguin, of 

 Lyons, first succeeded in preparing the crimson 

 dye on a large scale, hy acting on aniline with 

 hi-chloride of tin. Its manufacture and appli- 

 cation in dyeing were rapidly developed in 

 France, among others hy Verguin and the 

 Renard brothers, and in England especially by 

 the house of Simpson, Maule & Nicholson. To 

 this color, or to particular hues of it, have been 

 given by different manufacturers a variety of 

 names, such as magenta, roseine, fuchsine (now 

 somewhat commonly, but improperly, changed 

 to fuchsia, and by Prof. Dussauce to futschine), 



&G. 



From the first discovery of a brilliant dye 

 from aniline, it became of course a matter of 

 interest to be able to produce the latter mate- 

 rial in large quantities, and more cheaply than 

 could before be done ; and as these objects 

 were presently accomplished by operating on 

 benzole, it will be important here briefly to 

 trace the relations and show the nature of this 

 substance. 



When bituminous coal, placed in gas-retorts, 

 is distilled by application of a high heat, some 

 40 per cent, of it is volatilized and driven out 

 of the retorts, the remaining 60 per cent, con- 

 stituting the coke ; and the volatilized portion 

 being made to pass through the "hydraulic 

 main " and a succession ojf other condensers, 

 its condensible or liquid and solid matters are 

 chiefly arrested in these, while the mixed illu- 

 minating gases and some impurities pass on to 

 the proper reservoir. The condensed portions 

 altogether constitute the coal-tar. This con- 

 sists mainly of bodies which, when isolated, 

 have the form of oils (the coal-oils), and of a 

 tarry or pitchy residue, from which many 

 solids, crystallizable or otherwise, can be sepa- 

 rated. From the entire coal-tar some forty or 

 more distinct chemical substances (solids, liq- 

 uids, and gases) have, upon analysis of it, been 

 obtained. 



When coal-tar is hy itself placed in a retort, 

 and redistilled, the temperature being slowly 

 and gradually raised, the products that are first 

 for a time obtained are oils, those which pass 

 over at temperatures successively higher heing 

 of different composition, and more and more 

 dense or heavy. The oils which thus volatilize 

 at temperatures reaching to about 212 F., and 

 which are usually collected together, constitute 

 the " light oil " or " crude coal-naphtha." This, 

 in commerce, is more commonly known as 'ben- 

 sole or benzine, although the single oil which 

 (when pure) properly takes these names, forma 

 only a certain percentage of its whole bulk. 

 Among the many products which the entire 

 coal-tar, upon analysis, yields, are the solid, as 

 naphthaline, paranaphthaline, cumidine, paraf- 

 fine, &c. ; the liquid bases, as methylamine, ani- 

 line, chinoline, toluidine, &c. ; the liquid acids, 

 as the rosolic, brunolic, phenic or carbolic, 



&c. ; the liquid neulral bodies, as water, ben- 

 zole, toluole, cumole, &c. ; and gases, as ammo- 

 nia, &c. The quantity of aniline thus directly 

 separable from coal-tar is, however, small, and 

 the process is not remunerative. 



The light coal-oil or naphtha is a yellow or 

 brownish liquid, and when purified, lias a spe 

 cific gravity of from .70 to .85. The amount of 

 henzole proper contained in the naphtha varies 

 in different samples, being in some very small. 

 Benzole, first separated by Faraday from oil-gas, 

 was so named by Mitscherlich (1834), as being 

 procured by him from benzoic acid, distilled 

 with baryta. The fact of its forming a consid- 

 erable portion of coal-naphtha was later shown 

 by Mansfield, an English chemist ; though the 

 practical method of procuring it was brought 

 out on the continent, about 1850. French 

 chemists named the substance benzine; and 

 under this name, and that of "benzine-collas," 

 it became familiarly known as useful for re- 

 moving grease from cloth, &c. Benzole, as 

 obtained from naphtha, is not usually entirely 

 free from mixture with oils homologous with 

 it, as toluole, &c. At ordinary temperatures 

 it is a colorless, highly mobile liquid, of an 

 aromatic odor, and at 59 F. has a specific 

 gravity of about .85. Its composition is repre- 

 sented by Ci 2 Hc. 



Mitscherlich found that the strongest nitric 

 acid readily attacks benzole, one equivalent of 

 its hydrogen becoming replaced by one of 

 hyponitric acid, and a new compound a heavy, 

 yellowish oily liquid being produced, the com- 

 position of which is, therefore, CisEUNO^ This 

 he termed nitro-benzole. In preparing it, the 

 reaction just stated is secured by simply allow- 

 ing a fine stream of benzole and another of 

 concentrated nitric acid to run together in a 

 worm or long glass tube, kept well cooled, the 

 resulting product being then treated with 

 water and carbonate of soda. Nitro-benzola 

 has the odor of oil of bitter almonds, and ha. 

 hence hecome much used, under the name of 

 "essence of mirbane," for scenting soaps and 

 for other like uses. Zinin's mode of procuring 

 aniline from this oil by sulphide of ammonium 

 has been already referred to ; but as it was not 

 economical, many other methods were tried, 

 among these being that by means of nascent 

 hydrogen, set free by zinc and an acid, and 

 that with acetate of iron. By a modification 

 of the last-named reagent, introduced by M. 

 B6champ, the process being distinguished as 

 that with "ferrous acetate," it is, that aniline 

 can he cheaply prepared by the ton, and that 

 all the aniline of commerce is now obtained, 

 In this process, 2 parts of nitro-benzole, 2 of 

 concentrated acetic acid, and 3 of iron filings, 

 are placed together in a retort : the application 

 of heat is unnecessary, the chemical reaction 

 giving rise to sufficient heat to distill over a 

 mixture which is found to contain aniline, its 

 acetate, and some nitro-benzole. Redistilling, 

 and treating the distillate with fused caustic 

 potash, the aniline separates as an oily layer. 



