684

DYEING AND CALICO PRINTING.

exposed to the air, when the ammonia evaporates and pure aurin remains.Aurin, heated to i8o° C. with alcoholic ammonia, yields red corallin.

According to H. Fresenius, the rosolic acid obtained by Caro and Wanklyn,on treating an acid solution of a salt of rosaniline with nitrous acid andboiling the residue, is not identical with the phenol-rosolic acid. He pro-poses for it the name of pseudo-corallin.

33. Derivatives of Resorcin.—If resorcin is heated to ig5° C. withanhydrous phthalic acid, we obtain fluoresceine. It crystallises from alcoholin small deep brown crystals. If thrown down by acids from its potassicsolution it takes the form of a brick-red powder. With ammonia it yields ared solution, which even when very dilute displays a magnificent greenfluorescence. Fluoresceine dyes wool and silk a fine yellow without mordant.

In alkaline solution it is converted by zinc powder into colourlessfluoresceine, which recovers its colouration under the influence of oxidisingagents. If heated strongly with sulphuric acid and poured into water, it givesrise to a red deposit, which dissolves in alkalies with a blue colour, and isrendered blue by zinc-powder. The red liquid may be used for dyeing blue onthe principle of the indigo-vat, but the colour is neither beautiful nor fast.Fluoresceine is in many respedts analogous with litmus.

34. Derivatives of Hydroquinon.—If hydroquinon is heated to 130° to140° C. with concentrated phthalic acid two produfls are formed: thephthalein of hydroquinon, which is colourless, and an isomer of alizarin, ofa red colour, to which Grimm has given the name quinizarin.

To obtain the latter body the produdt of the readtion of phthalic acidand sulphuric acid is dissolved in alcohol, and water is added, when quini-zarin is deposited in orange flocks, which when dried at 100° to no° C.become red and crystalline. The ethereal and sulphuric solutions present ayellowish green fluorescence, similar to that of the munjistin of Stenhouse.

Grimm suggests that munjistin and quinizarin bear the same relation toeach other as do purpurin and alizarin. Quinizarin melts at iga° to 193° C.,and sublimes in feathery crystals. Its solution in the alkalies is blue ; itsammoniacal solution and that formed with alkaline carbonates is more violet.It gives a blue-violet compound with magnesia, and a red-lake with alumina.

Quinizarin may be easily confounded with alizarin, and dyes mordantedcotton in the same manner.

35. Derivatives of Pyrocatechin.—If pyrocatechin is heated withanhydrous phthalic acid and with sulphuric acid, on adding water a greenishliquid is produced, which with potash gives a blue colouration that soondisappears. Baeyer thinks that this substance may be analogous to thecolouring matter of logwood.

36. Gallein.—This colouring matter has been noticed on p. 508. Thefollowing additional particulars may be useful. Gallein dyes tissues mor-danted with alumina and oxide of iron in the same manner as the red woods,but the shade is rather more blue. The colours are intermediate between thoseof peachwood and logwood. It is extremely probable that gallein belongs tothe family of the tin&orial wood pigments, and that it is the first member ofthe series which has been artificially prepared.

Gallin produces the same shades as gallein, and shows a marked analogywith hsematoxylin.