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DYEING AND CALICO PRINTING.

of a pale yellow colour, and forms beautiful crystals with the alkalies andalkaline earths. The lime-salt is largely manufactured by Messrs. Robertsand Dale, and is known under the trade-names of Manchester Yellow andJaune d’Or. Its tinctorial power is still greater than that of picric acid, towhich it is in many respeCts analogous. Indeed, it may be regarded as apicric acid, in which the radical phenyl is replaced by naphthyl. It producesupon silk, wool, and leather bright shades of a true gold colour, without thegreenish cast of picric acid. These colours bear the steaming process, whichis not the case with those obtained with picric acid.

It was at one time thought that alizarin had been obtained artificially fromnaphthalin. This opinion proved to be unfounded, but artificial alizarin, aswe shall see below, is produced by another of the coal-tar products.

Many of the coloured reactions of naphthalin and its derivatives invitefurther research.

ANTHRACEN COLOURS.

Artificial Alizarin.

Anthracen is a solid body, existing in the heavy oils of coal-tar. It is metwith in the last portions, which distil after napthalin. It is not equallyplentiful in all tars, but is chiefly found in those which are rich in benzol andnaphthalin, poor in toluen. According to Berthelot, toluen at a red heatyields anthracen as the principal product of its decomposition. If theexistence of anthracen in coal-tars is due to the previous destruction of apart of the toluen which they contain, the rarity of the one substance mustcorrespond with the abundance of the other. On the large scale anthracenis prepared as follows :—If coal-tar is distilled in the usual manner it yieldson the average per ton 13 to 14 litres of ammoniacal gas-liquor; 29 to 30of very light oils, containing benzol; go to 100 of light oils, containing alittle benzol. If the distillation is continued, 300 to 312 litres of heavy oilsare collected, and the residue is merely hard pitch. The heavy oils consist ofnaphthalin, phenol, cresol, and similar products, and contain besides more orless anthracen. The last-mentioned body passes over towards the end of theprocess. When the fatty matter which distils over shows a yellowish greencolour, and congeals to a pasty consistence on cooling, it is collected separately.It contains about 20 per cent of anthracen, and is used as the chief materialfor its preparation. The mass is placed in a centrifugal machine to expelthe oil as far as possible. The residue, which still contains much oil, is heatedto about 40° C., and introduced into a powerful hydraulic press, which shouldbe provided with plates capable of being heated like an oil-press. The residue,after pressing, contains about 60 per cent of pure anthracen. In this stateit is a greenish, tolerably dry mass. It is then treated with light tar-oil orwith petroleum-naphtha, boiled and allowed to cool, or extracted by percolation.The light oil dissolves the residue of naphthalin and the heavy oil, whilstpure anthracen moistened with naphtha remains behind. This pureanthracen is again extracted in the centrifugal, placed in a boiler, and heatedto the melting-point, when the residues of the light oils distil over. Thereremains a greenish-white, paraffin-like mass of fine crystalline fradure, con-taining g5 per cent of pure anthracen, and melting at 205° to 208° C. Bysublimation pure anthracen is obtained in small lamellar crystals, which meltat from 212° to 215°. A trustworthy method for determining the amount of