Coal-Tar Colors.

The Living Age 960, 25.10.1862

One of the most prominent features in the Eastern Annex at the Exhibition is the gorgeous display made by the artificial coloring matters derived from coal-tar. Messrs. Perkin and Son, the originators of this new and important branch of industry, exhibit a very complete and beautiful collection, illustrating their manufacture of mauve dye or aniline purple. Commencing with the crude coal-tar, we have a complete series of the different stages of its manufacture, up to a gigantic block of the pure dye itself, upwards of a cubic foot in bulk, and said to be the product of the distillation of two thousand tons of coal. In illustration of the tinctorial properties of this dye, they exhibit a large glass jar, filled with a beautiful violet solution, the color of which is said to be communicated to it by one grain of the dye. As a pendant to this, there is shown on the opposite side a similar jar, filled with thick black coal-tar, - an amount which, by appropriate treatment, would yield one grain of the coloring matter. The centre part of the case is filled with dyed specimens of all kinds, in skeins and fabrics, together with the various mordants used, illustrating the varieties of tint produced by modifications in the dyeing process. This collection is very complete, and has attracted great attention from our intelligent foreign visitors, who for the last month have been devoting themselves, officially or privately, to the examination of the substances in this class.

Specimens illustrating the manufacture of the beautiful magenta dye, a close relative of aniline purple, and obtained from the same source, are contributed by the firm of Messrs. Simpson, Maule, and Nicholson. The most striking object in this case — indeed, we might almost say one of the lions of this department of the Exhibition — is the magnificent crown, formed of enormous crystals of acetate of rosaniline, the chemical name of the pure magenta dye. The remarkable property which this body possesses of reflecting, when in the solid state, the opposite color to that which it gives when used as a dye, is here shown in a striking manner. The color of the crystals is of a remarkably brilliant and rich metallic green, only equalled by the shade observed in the plumage of some birds, and on the bodies and wings of a few insects. The production of a crown like this forcibly illustrates the gigantic scale of operations upon which this firm does business; the value of the substance composing the crown, merely regarding it in the light of a coloring matter, is upwards of £700, and we understand that the solution from which it was crystallized contained more than £2,000 worth of material. The scientific student will feel an interest in examining the enormous size of some of the crystals composing this crown, and of others lying in a dish by its side, and then comparing them with the almost microscopic size of those exhibited in one or two other cases. Most unfortunately the gorgeous brilliancy of the green metallic reflection from this salt is gradually failing under the influence of light, giving place to a somewhat unpleasant brown tarnish. The original color may still be seen upon close examination of those portions of the material which are in the shade, especially if the visitor directs his attention to two smaller crowns which have recently been deposited by this firm on a neighboring counter; but the effect, beautiful as it is even now, bears no comparison to the exquisite lustre which the large crown bore on our first inspection of it, as it was being deposited in its case. In other parts of the collection exhibited by the same firm, are displayed materials illustrating the manufacture, in all its stages, from the coal tar naphtha, nitrobenzol, arsenic acid, up to the salts which possess and confer the color. There is also a specimen of a new yellow dye derived from aniline, respecting which we regret that further particulars are not given, as we understurd it possesses many valuable and muchdesired qualities. It is also to be regretted that these exhibitors have not, like the Messrs. Perkin, shown specimens dyed by these different colors. In addition to the cases already mentioned, there are other specimens of aniline dyes in different parts of the building, including some of the new aniline green or dianthine, respecting which we may remark, that unless the coloring matter possess other valuable properties, such as extra permanency, ease of application, cheapness, etc., we scarcely think that the tint here shown will cause it to prove a formidable rival to the green coloring matters already in use. All these aniline dyes can claim Mr. Perkin as their parent, and thus this gentleman deserves more prominent notice than would even be accorded to him from merely an inspection of his case. That and the one shown by Messrs. Simpson may be regarded as almost complete illustrations of a manufacture which has so rapidly become an important branch of our national industry. These cases will be looked upon with much interest by our readers after the very complete history of the manufacture lately given by Dr. Hofmann before the members of the Royal institution and reported in our pages, and they will not fail to appreciate the intelligence of the chemist who succeeded in converting some of our most nauseous and repulsive byproducts of gas manufacture into these lovely colors, and the commercial skill which has enabled them to be economically prepared on such to scale as to enable England to cease from being a dye-importing, and become a dye-exporting, country.

London Review.

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