646

DYEING AND CALICO PRINTING.

This mixture does not attack the dodtors, but the black produced is lessintense than that obtained by Lightfoot’s process, and the price is a littlehigher. Cam. Kcechlin replaces the ferricyanide of ammonium by ferricyanideof potassium and tartaric acid, and ages at a temperature of 50° to 60° C.

Lauth uses the following mixture :—

Tragacanth mucilage. ^ litre.

Torrified starch.650 grms.

Water.950 ,,

Chlorate of potash .150 ,,

Sal-ammoniac .50 „

Hydrochlorate of aniline.400 „

On the other hand he incorporates—

Wheat starch .500 grms.

Sulphide of copper .150 „

Water.250 „

When required for use the two are mixed together. The pieces are aged at20 0 to 30° C.

The sulphide of copper is prepared by precipitating a solution of sulphateof copper with sulphide of sodium.

Muller prepares a black for printing as follows :—Dissolve—

Water .‘. $ litre.

Chlorate of potash . 20 grms.

Sulphate of copper .30 ,,

Sal-ammoniac ..16 „

Hydrochlorate of aniline.40 „

The mixture is heated in the water-bath to about 6o°. After two or threeminutes the solution swells, and readily boils over. If, after the lapse ofseveral hours, the thick mixture is not an intense black, it is once more heatedto 60° C. The resulting paste is exposed for two days to the open air, thenwashed on a filter long and carefully, until no more saline matter can be dis-covered in the filtrate. A black of a more blue shade is obtained by using, asfinal wash-liquor, 1 litre of water in which 20 grms. of soluble aniline bluehave been dissolved. It is thickened with albumen, of which it requires alarge quantity, printed, and well steamed.

Lightfoot’s method of applying aniline black to animal fibre, or to mixedfabrics, such as delaines, &c., is described as follows, in his Specification ofSeptember nth, 1865 (No. 2327):—“ For mixed goods I wince or steep themin a solution of hypochlorite of lime,—or a mixture of hypochlorite of lime,hydrochloric acid, and water,—for the purpose of preventing the deoxidisingproperties of the animal fibres and substances. When the wool or animalsubstance is thoroughly oxidised to its maximum, and in a fit state to receivethe aniline black, it may be known by the following simple test:—Take a dilutesolution of permanganate of potash in two test-tubes, and into one put a pieceof the oxidised wool, and into the other a piece that has not been oxidised,and apply a gentle heat; the solution containing the one that is in a fit stateto receive the aniline black remains pinky, but the other is decolourised imme-diately. The proportions for preparing the wool are about as follows:—I takefor every pound of cloth, wool, yarn, silk, delaine, feathers, or animal sub-stance (well cleaned), 6 gallons of water at about 100° F., 2J ounces by weight