COLOURS FROM ANILINE.

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with soap gradually destroys the colour; (c). Reducing agents, as sulphurousacid, protochloride of tin, hydrosulphuret of ammonium, and protosulphateof iron, also rapidly destroy this colour.

Purple of the Ancients.

The use of a purple colour extracted from certain univalve molluscs datesback to a very remote period of antiquity. The tissues, chiefly linen andwool thus dyed, were always held in high esteem, and were extremelycostly. The real art of applying this dye, and the precise kind of mollusc,are to a great extent matters of conjecture. Dr. Sacc has published alengthy, yet very interesting, paper on this subject.* It is a positive faCtthat in different parts of the seas of our globe in hot, temperate, and evencold climates molluscs are found which contain in a peculiar organ a verythick yellowish green liquid, which gradually imparts to tissues a purplishcolour. A Mr. William Cole, of Bristol, obtained a high reputation by thefaCt that he discovered, in the year 1663, the mollusc which had been for sometime used by a dyer of that city to impart to tissues a brilliant and fast purplecolour. Messrs. B. de Jussieu, Reaumur, Duhamel, and Bancroft experimentedin the course of the last and beginning of this century with various molluscsfor the purpose of dyeing tissues.

M. Gonfreville records that in some parts of India a mollusc, known as amurex, is kept alive in sea-water until a sufficient number is obtained;from 4000 to 5000 of these shell fish are required to dye 1 kilo, of wool, forwhich purpose the shells and contents are broken up while placed in sea-water, and left standing for several days afterwards in leaden vessels. Thewool to be dyed is immersed in the liquid, or sometimes the liquid is appliedto the tissue by means of a brush. According to M. de Saulcy, the ancientsderived their purple from the Purpura hemastoma , known to Pliny as Buccinum ,and also from the Murex brandaris , which Pliny called Purpura. At Athensand Pompeii large quantities of these shells have been discovered lying inheaps close to ancient dye-works. The ancients distinguished Tyrian andByzantium purple; the former had the colour of coagulated blood ; the latterexhibited a more violet hue. Both were in every respeCt fast colours.

Colours Derived from Aniline and Kindred Bodies.

Aniline was first discovered in 1826 by Unverdorben among the products ofthe destructive distillation of indigo. Runge extracted from coal-tar a sub-stance which he named Kyanol, which, when treated with hypochlorite oflime, yielded a brilliant blue colour, and which was afterwards proved to beidentical with aniline. Up to 1856 this substance remained a mere laboratorycuriosity, devoid of industrial application. To Runge the honour is, therefore,due of having first drawn attention to the possibility of obtaining aniline fromcoal-tar, and of applying it to the production of tinctorial substances.Fritzsche found that aniline yields with aqueous solution of chromic acid abluish-black precipitate. In 1853, Beissenhirtz described the blue colourresulting from a mixture of aniline, bichromate of potassa, and sulphuric acid.Stenhouse, when experimenting on furfurol, found that aniline and its acetate

* Bulletin de la Societe de Mulhouse, vol. xxvi., p. 305.