DETECTION OF DYES. 667

If the green is a chrome-green, such as Guignet’s, oxide of chrome willremain in the ash, which will have a dull green colour.

If the green is arsenical, such as Scheele’s green, a piece of the cloth, onburning, gives a green tinge to the flame. The ash is extra&ed with nitric orhydrochloric acid. The clear solution is freed from excess of acid by evapo-ration at a gentle heat, diluted with a little water, and mixed with ammoniain excess. A blue colour will appear from the copper present in the arsenicalgreens.

On woollen and worsted goods, if soda dissolves off extradl of indigo, theyellow portion will probably be fustic. If the blue is a Prussian or royal, theyellow will generally be bark or flavin.

F. VIOLET.

The violets here indicated are:—

1. Common aniline violet.

2. Iodine (Hofmann) violet.

3. Madder purple.

4. Alkanet violet.

5. Orchil violet.

6. Logwood violet.

7. Cochineal purple.

We first steep a swatch in solution of chloride of lime. If it resist it isalkanet violet. If there is a change of colour we have one of the six others.

A second swatch is then steeped in lime-juice. If the violet be notheightened in tone we have one of the two aniline violets. If it becomes red,or even yellow, we may have madder, orchil, cochineal, or logwood. Todistinguish these a swatch is steeped in chloride of lime, then washed inwater, and placed in an acid solution of yellow prussiate of potash. Asmadder and cochineal purples have oxide of iron for their mordant, whichremains attached to the fibre, Prussian blue is formed in case of these twocolours. If there is no blue colouration, we have orchil or logwood. Itremains then to distinguish between—

1. Madder purple and cochineal purple.

2. Orchil violet and logwood purple.

3. Common aniline violet and Hofmann violet.

A fresh swatch of the cloth is steeped in chloride of lime. It is turned aNankeen yellow if dyed with madder, and is completely discharged if dyedwith cochineal.

A swatch steeped in milk of lime becomes greyish, and, finally, colourlessif dyed with logwood; but changes to a violet-blue if dyed with orchil.

A swatch steeped in hydrochloric acid diluted with three times its measureof water becomes blue-violet, and after washing with water a little redder, incase of common aniline violet. In case of iodine (Hofmann’s) violet, thefabric becomes blue, greenish, and after washing with water a clear lilac, orpearl-grey, according to the original depth of shade.

A red ash (iron mordant) indicates madder or cochineal. A white ash (alummordant) indicates logwood. Absence of ash shows the aniline violets.

A peculiar pigment violet is produced by a mixture of ultramarine and ver-million. If this is treated with dilute acid the blue is destroyed, while the red