THE ANILINE COLOURS.*
IN the year 1856 a young English chemist, experimenting with some of the products derived from coal tar, discovered a new dye of unexampled brilliancy and beauty. Though the fact that Aniline in certain combinitions assumed a beautiful blue or violet colour had not escaped the notice of previous experimenters, the credit of rendering an aniline colour available as a dye, it is universally admitted, is due without qualification to Mr. W. II. Perkin. The discovery of mauveine by that gentleman laid the
foundation of an entirely new branch of industry, which within. the brief interval that has since elapsed has expanded and developed itself with a rapidity almost without precedent. Very probably the chemist himself, when conducting his experiment, had no adequate presentiment of the momentous consequences it. involved. Already, however, is the industrial revolution he was then virtually working an accomplished fact. No sooner was Mr. Perkin's discovery made known than it rivetted the attention of chemists in every country. A whole army of experimenters in England, France, and Germany immediately commenced to prosecute further investigations into the subject, and with such energy and effect did they pursue their researches, that presently fresh discoveries and inventions began to be announced with bewildering rapidity. The zeal with which theoretical experimenters cultivated the new field was, however, more than rivalled by the eagerness with which, in manufacturing industry, each new discovery, as it was made, was seized upon and rendered subservient to practical ends. Curiously enough, the original inventor was not the first to bring the new dyes into commerce. It cost him two years of effort before he succeeded in establishing the manufacture of the new material in his own country. In the mean time, he was anticipated by French chemists and manufacturers, who, availing themselves of the process revealed in the English patent, at once began to produce the new dye. "One who only considered the state of the industry at this time in the two countries," remarks Dr. Hofmann, in the report appended to the present volume, "would have said that the invention belonged to France, and had only been imported into England." While, however, the honour of the original invention belongs to England, the credit, not only of achieving the first great industrial success, but also of making the next important advance in the way of invention, cannot be denied to France. Aniline red was first produced in Lyons in 1859, a date distinguished by the sanguinary victories in Italy, from one of which the new dye received its name. "Scarcely three mouths after the production of magenta was commenced in Lyons, it was transplanted to Mulhouse; then, crossing the Channel, it became established in England, at London, Coventry, and Glasgow ; and was not long before it was taken up in Germany." New discoveries and inventions now followed thickly upon one another, and the year following that of the invention of magenta was marked by the production of aniline blue. So rapidly did this new member of the group of the coal-tar colours gain the victory over the blue dyes hitherto in use, that less than a year after its invention it took ten manufactories in Germany, England, Italy, and Switzerland to satisfy the demand it bad already created. The unprecedented rapidity with which the new dyes were adopted in the civilized nations of the West was, however, by no means the only remarkable incident in the history of their early successes. In the words of the report above quoted :—
" Whilst the manufacture of Aniline colours thus became European, their consumption spread still further ; and now could be observed this unique fact in the history of commerce,—the West supplied the East with colouring matters, sending its artificial dyes to the confines of the globe, to China, to Japan, to America, and the Indies,—to those favoured climes which up to the present time had supplied the manufactories of Europe with tinctorial products. This was a veritable revolution. Chemistry, victorious, dispossessed the sun of a monopoly which it had hitherto always enjoyed. At the beginning of this century, when mythological language was in vogue, it would have been said that Minerva had triumphed over Apollo. But it was not sufficient to extract colours from tar and send them to China. . . . In order to apply these colours, the processes being altogether different from those followed by the Chinese, and their employment requiring the assistance of substances which were unknown to them, it was necessary . . . to undertake the education of the Chinese dyers. This difficulty did not for a moment stop the European manufacturer ; he sent to China and Japan not only the workmen who should teach his customers the way to apply the colours with which he supplied them, but also the chemical products necessary for their manipulation, such as sulphuric acid and absolute alcohol, which were before unknown to them. Thus arose considerable dealings with the East, the quantities sold by European manufacturers. in 1864, 1865, and 1866 amounting to several millions of francs."
At the period of the London Exhibition in 1862, but six years after the original invention by Mr. Perkin, chemists had already succeeded in producing nearly all the principal colours from aniline. At that time only aniline black and green were still wanting, but the gap was soon filled up. In the words of our authors, "The gamut of colouring matters derived from aniline is now complete ; we have red, orange, yellow, green, blue, indigo, and violet." One singular result of recent research has been to make rosaniline or aniline red the parent of all the other colours, blue or violet, which he requires. It is to Dr. Hofmann that we owe a more intimate knowledge of the chemistry of these colours. His researches on the subject are among the most brilliant triumphs of chemical analysis, and richly deserve the epithet 'classical' which M. Reimann applies to them. Nor were Dr. Hofmann's researches simply of theoretical value. No sooner had he arrived at the true theory, than he was able to proceed deductively to the creation of new and valuable products which are known as Hofmann's violets. We are strongly tempted here to administer to our readers a small dose of formulae, but must content ourselves with observing that Dr. Hofmann's analysis showed aniline blue to be nothing more than triphenylic rosaniline; in other words, that the substitution of three equivalents of the radical of aniline (phenyl) for three of hydrogen turned magenta into blue ; while the substitution of two equivalents, and, again, of one equivalent, changes magenta into the blue and red shades of violet respectively. The step by which Dr. Hofmann proceeded from the phenylation to the ethylation of rosaniline,—thereby at once conclusively proving the truth of his theory, and producing the charming colours bearing his name,—is one of those beautiful instances of scientific generalization which are only possible to men of theory, and which to practical men appear like feats of genius.
The bare enumeration of the uses to which the new colours are put would exhaust almost all the apace at our command. Not only are they applied to the dyeing of textile fabrics and calico-printing in vast quantities, but for numberless other branches of industry they have almost entirely supplanted the colouring agents formerly employed. Among the purposes, useful or ornamental, to which we find them put, are the tinting of paper, of inks for writing and typography, of paper-hangings ; they are employed in water-colour painting, the colouring of designs and photographs, the lacquering of wood, the tinting of straw for bonnets, and of pearl, bone, and ivory ; the imitation of pearls and precious stones, the decoration of glass and porcelain to imitate enamel, the soaking of the tissues of objects for microscopical and anatomical purposes, the tinting of candles and wax tapers, of white vinegar and syrup of raspberries, the blueing of linen, and the colouring of confectionery :—
"The art of perfumery also has recourse to the Aniline dyes for the coloration of essences, soaps, cold cream, pomades, rice powder, &c. Their application to these different uses is self-evident, and granting the utility (a very questionable one) of the unguents with which the fair sex love to anoint themselves, we are constrained to admit that the introduction of the Aniline dyes to this branch of industry has been of undoubted service. They have superseded the metallic substances,— the preparations of mercury, of bismuth, and of lead,—which were almost all injurious to health. As, however, it is not our wish [add the gallant authors of the French Exhibition Report] to destroy pleasant illusions, we shall not enter into more ample details on so mysterious a subject."
Dr. Reimann's handbook, as the completest practical treatise that has yet appeared in the language, is a work with which no chemist engaged in any branch of the Aniline industry can afford to dispense. While the author gives as much of the theory as any manufacturer is likely to require, his account of the practical operations of the manufacture, including all the most recent pro cesses and improvements, leaves nothing to be desired. The name of the English editor, himself a chemist of note, is sufficient guarantee of the trustworthiness of the work. It was a happy thought to add to Dr. Reimann's technical treatise a translation of the report on the coal-tar dyes in the late Paris Exhibition. It is written in a clear and attractive style, and cannot fail to interest the general reader equally with the technical student.
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