666

DYEING AND CALICO PRINTING.

E, GREENS.

The greens most commonly met with in dyed goods are of three kinds ;—

1. Greens obtained with a mixture of yellow and blue.

2. Aniline (aldehyd) green.

3. Iodine green.

Lao-kao, chlorophyl, &c., are rarely met with. The greens made up ofyellow and blue are .—

1. Indigo and picric acid.

2. Indigo and vegetable yellows.

3. Prussian blue and picric acid.

4. Prussian blue and vegetable yellows.

5. Aniline blue and vegetable yellows,

6. Aniline blue and picric acid.

In these mixed greens the blues form the bottom and, excepting anilineblue, are insoluble in alcohol. All the yellows given are soluble in alcohol.Hence a green, soluble in alcohol with a green colour, must be a mixture ofaniline blue and yellow.

Into a small flask is poured some alcohol at 95 per cent, into which aswatch of the cloth is immersed. The alcohol is raised to and maintained atthe boiling-point for a few minutes on the water-bath. Two results mayfollow:—

1. The alcohol becomes yellow, and the tissue turns gradually more blue.

2. The alcohol becomes green, whilst the cloth grows paler, but without

altering its tone.

In the former case the bottom is indigo or Prussian blue. When the swatchhas given up all its yellow colour to the alcohol, it is taken out, washed inpure water, and placed in a glass with a solution of chloride of lime. If thebottom is indigo, the colour will be attacked, but if Prussian blue, it willremain unchanged. The alcoholic liquid remaining in the flask may containseveral colouring matters. It is divided into portions, which are then testedaccording to the instructions given for yellows.

In the second case we have aldehyd or iodine green, or aniline blue alongwith a yellow. In order to distinguish between these colours, we boil aswatch in dilute hydrochloric acid. The cloth becomes :—

a. Rose or lilac. . Iodine green.

b. Blue, the yellow being discharged .. .. Anilihe blue and a yellow.

c. Discharged, or yellowish. Aldehyd green.

If it be found that the green is a mixture of aniline blue and a yellow, the

nature of the latter may be determined as above directed.

A swatch may be placed in a solution of carbonate of soda, noting whether ablue colour is dissolved out. If so, the blue portion of the green is extra# ofindigo. If the swatch is turned a rusty colour by alkalies, the blue is a Prussian.This is most to be expected on cotton goods. If the green is blackened bysulphuretted hydrogen, and if a blue remains on carefully washing with adilute acid, chromate of lead is one of the ingredients. In this case, for cor-roboration, burn a swatch to ashes in a light porcelain—not platinum—capsule, and extract the ash with dilute nitric acid. If chromate of potashgives a yellow precipitate in the filtered liquid, chrome-yellow was originallypresent.