APPENDIX.

675

is employed which can be used at will either for cohobation or distillation.Toluen is introduced into this apparatus and quickly brought to a boil, and acurrent of chlorine is brought in contadt with its vapours, which are diredtedinto the cohobator, where the toluen and the chloride of benzyl formed are con-densed and fall back. When a thermometer immersed in the boiling toluenmarks 140° to 150° C., the current of chlorine is shut off and distillationbegins. All that passes over below 170° C. is collected separately, and is againtreated with chlorine. What distils between 170° and 180° is submitted to anew rectification. Finally, what goes over between 174 0 and 176° C. is nearlypure chloride of benzyl.

8. Diphenylamine yields a magnificent blue colour with concentratednitric acid, methyl-diphenylamine, which is obtained by treating diphenylamineby iodide of methyl at temperatures above ioo° C. It yields blue or violetcompounds with arsenic acid, the metallic nitrates, chlorides, iodides,bromides, iodine, chlorate of potash, sesquichloride of carbon, chloral, &c.

g. Cerise.—The trade name of a colour sold by the firms of Geigy, of Basle,and Knosp, of Stuttgardt. It is prepared from magenta residues, and dyesshades more inclining to a scarlet. After the crude magenta has been boiledin water and the pure magenta precipitated with common salt, carbonate ofsoda is added to the remaining liquid, and the precipitate thus obtained iscollected and dried. It is probably a mixture of rosaniline with chrysanilineand chrysotoluidine.

10. Coupier’s Aniline Reds.—Coupier dispenses with arsenic, and obtainsreds—(1) with pure or nearly pure aniline and nitro-toluen; (2) with ordinarycommercial aniline and common nitro-benzin; (3) with nitro-toluen and toluidineor with nitro-xylen and xylidine. In each case he adds perchloride of iron andhydrochloric acid. The two former mixtures yield reds identical with commonmagenta; the third gives a produdt which Coupier names roso-toluidine,toluidine-red, or xylidine-red. The ingredients to be used for the last-mentioned

colour are:—

Nitro-toluen . 95 parts.

Hydrochloric acid .65 ,,

To which are then added—

Toluidine.67 parts.

Perchloride of iron.7 or 8 parts.

The method of conducing the operation on the large scale is as follows:—Any of the above mixtures is placed in an enamelled cast-iron vessel, andheated gradually to 200° C. The progress of the readion is judged by theindications of a thermometer plunged in the mass, by the nature of thevapours given off, and by the appearance of the mixture, of which a specimenis taken from time to time. The produdt, on cooling, becomes a solid, brittlemass, like raw magenta-melt. It is powdered, boiled in water, and thecolouring matter is thrown down by means of carbonate of soda, and purifiedin the ordinary manner.

11. Hofmann’s Xylidin Red is prepared by heating a mixture of purexylidin and pure aniline with an oxidising agent. It is a splendid crimson-red colour, producing shades very similar to those yielded by magenta. It isevidently distindt from Coupier’s xylidin-red.