664

DYEING AND CALICO PRINTING.

Aniline Blues when burnt leave merely the ash of the fabric. On steepinga swatch of the cloth in alcohol we obtain a beautiful blue liquid, notreddened by citric acid. The liquid obtained from a logwood blue turns redat once if mixed with an acid. Dilute acids and solutions of the carbonatesof soda and potash produce no change. Concentrated acids turn the blue toa green, but washing in abundance of water restores the blue, in a somewhatfainter shade. Caustic soda turns the blue to a reddish-brown.

Prussian Blues.—Dilute acids produce no change. Concentrated nitricacid alters the shade to a green, which washing does not re-convert into blue.Solutions of alkalies, both caustic and carbonated, give a rust-colour (oxide ofiron), different from the red shade which caustic soda gives on aniline blues,and incapable of re-conversion into blue by washing in water.

Mixed Blues.—Vat-blue, in order to economise indigo, is sometimesw topped,” and in other cases “ grounded,” with the red woods,—especiallycamwood and sanders,—with cudbear, and even with yellows, as fustic. Inthis case sulphuric and muriatic acids should be applied, at first dilute andafterwards concentrated, noting if the liquid is turned red or yellow. In theformer case wood or weed colours are present. If a vat-blue, grounded withany other colour, is discharged with concentrated nitric acid, the colourremaining is not the clear yellow which unmixed indigo gives under similarcircumstances, but a brownish shade.

Ultramarine Blue (Pigment Styles).—The swatch is steeped for a timein a mixture of ether and alcohol, to remove any resinous matter with whichthe colour may have been fixed, and then moistened with hydrochloric acid.The colour disappears, with the smell of putrid eggs.

C. YELLOWS.

The yellows on whose nature we are able to pronounce are :—

1. Iron buff.

2. Picric acid.

3. Turmeric.

4. Fustic.

5. Weld.

6. Persian beries.

7. Bark (quercitron).

8. Chrome yellows and oranges.

9. Annatto.

I. In order to distinguish between these colours, we begin by ascertainingthe presence or absence of iron-yellow and of picric acid. To effedt this, twoswatches of the cloth are cut off, and the one is steeped in a luke-warm andslightly acid solution of yellow prussiate of potash, and the second in a hotsolution of cyanide of potassium. If the prussiate gives a blue colour we maybe certain that the sample is an iron-buff. If the cyanide gives a red colourationpicric acid is present. Picric acid is extracted by alkalies and albumen.Acids produce no change.

II. If neither of these results appears iron and picric acid are both pro-nounced absent. We then take a fresh swatch and put it in a boiling solutionof 1 part of soap in 200 of water. The following reactions may then takeplace;—