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Cotton and linen are dyed red with madder, Cochinéal, which gives so fine a red to wool, by the nitro-muriate of tin, communicates only a dirty red to cotton and linen, by the same means.

Madder reds are of two kinds. 1. The common madder red, which is formed by impregnating the cotton or linen with galls, and afterwards alumed, and then putting them into the madder bath. 2. The Adrianople, or Turkey red. This process was brought from the East. It is more durable and more beautiful than the common red. The cloth is first impregnated with oil, then with galls, and lastly, with alum. It is then boiled for an hour, in a decoction of madder, which is commonly mixed with a quantity of blood. After the cloth is dyed, it is plunged into a soda ley, in order to brighten the colour. The chief difficulty is in the application of the mordant, which is the most complicated employed in the whole art of dyeing.

Cotton may be dyed scarlet by the murio-sulphate of tin, cochineal, and quercitron bark; but the colour is extremely fugitive.

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Of Dyeing Yellow.

The chief yellow dyes are weld, sumach, fustic, turmeric, and quercitron bark.

Weld is a vegetable that grows commonly in this country.

Sumach is a shrub growing naturally in the South of Europe.

Fustic is the wood of a tree which grows in the West Indies.

Quercitron is the bark of a tree which is a native of North America,

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It is not possible to give to cloth a permanent yellow colour without the use of mordants. Alum is the most usual mordant. Wool is dyed yellow by weld, by the use of alum and tartar. Quercitron bark gives nearly the same colour, but more abundantly, and it is rather cheaper than weld. The process is as follows: boil the cloth for an hour or more in a solution of alum, and then immerse it in a bath of quercitron bark. Next add a small quantity of clean powdered chalk, and continue the boiling for eight or ten minutes. The yellow thus given will be as good as that obtained from weld.

If very bright yellows are required, the tin mordant must be used; and sometimes alum is added to the tin.

If an addition of tartar be made to the mordant, the yellow will have a slight tinge of green.

If an orange or an aurora be required, a small portion of cochineal must be added.

Silk used formerly to be always dyed yellow with weld, but quercitron bark is now found to answer equally well, and at less expense. The proportion should be from one to two parts of bark to twelve pounds of silk, according to the particular shade of colour wanted. The bark, powdered and tied up in a bag, should be put into the dyeing vessel whilst the water is cold, and as soon as it becomes blood warm, the silk previously alumed should also be put in and dyed as usual, and when the shade is required to be deep, a little chalk or pearl-ashes may be added towards the end of the operation.

When very lively yellows are required, a little of the murio-sulphate of tin may be employed as a mordant in addition to the alum. Annotto com

municates an aurora colour to silk, the colour of the annotto is extracted by means of alcali.

To dye cotton and linen yellow, proceed as follows. Take a sufficient quantity of the acetate of alumine, formed by dissolving one pound of sugar of lead, and three pounds of alum, and the cotton or linen being properly cleansed, immerse it in this mordant (which ought to be blood warm) for two hours, let it be then taken out and moderately pressed or squeezed over a proper vessel, to prevent the unnecessary waste of the mordant, dry it in a stove heat, and soak it again in the aluminous mordant; it is then taken out, and again pressed and squeezed as before; after which, without being rinsed, it is thoroughly wetted in as much, and only as much, lime-water as will conveniently suffice for that purpose, and afterwards dried. The soaking in the acetate of alumine may be again repeated, and if the shade of yellow is required to be very bright and durable, the alternate wetting with lime water and soaking in the mordant may be repeated three or four times. Thus a sufficient quantity of alumine is combined with the cloth, and the combination is rendered more permanent by the addition of some lime. The dyeing both is prepared by putting 12 or 18 parts of quercitron bark, (according to the depth of the shade required,) tied up in a bag, into a sufficient quantity of cold water. Into this bath the cloth is to be put, and turned round in it for an hour, while its temperature is gradually raised to about 120°, it is then to be brought to a boiling heat, and the cloth allowed to remain in it after that only a few minutes. If it be kept long at a boiling heat, the yellow acquires a shade of brown.

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To dye nankeen yellow, boil the cotton in a solution of carbonate of potash, and then dip it in a solution of the red sulphate of iron.

Of Dyeing Blue.

There are but few substances capable of furnishing blue dyes. The only vegetable products are indigo and wood. Indigo is a rich blue colour procured from the fecula of a species of plant that is cultivated in America, and also in the East Indies. The colouring matter is extracted by water, and is at first green, but immediately absorbs oxygen, and then assumes a blue colour. It becomes at the same time insoluble in water, but is soluble in sulphuric acid.

As indigo has a very strong affinity for wool, silk, cotton, and linen, a mordant is unnecessary in dyeing with it. The colour is very permanent, because the indigo being already saturated with oxygen, to which it owes its blue colour, is little liable to be decomposed. But it is essential that the indigo be applied in a state of solution in order to attach itself to the cloth.

A solution of indigo in the sulphuric acid is used for dyeing wool; this is called Saxon blue, and it gives a very beautiful colour. But it will not do for dying cotton or wool, because their affinity for indigo is not sufficiently great to enable them to decompose the sulphate of indigo.

To dye by the sulphate of indigo, dissolve one part of indigo in four parts of concentrated sul. phuric acid; add to the solution one part of dry carbonate of potash, and dilute the whole with eight times its weight of water.

Boil the cloth for an

hour in a solution of five parts of alum, and three of tartar, for every thirty-two parts of cloth. The

cloth is then to be put into a bath of sulphate of indigo, diluted according to the strength of shade required, and kept till it has acquired the desired colour. The use of the alum and tartar is not to act as mordants, but to facilitate the decomposition of the indigo. The alcali is added to the sulphate for the same reason.

Another use of these substances is, that they protect the cloth from the action of the sulphuric acid, by neutralizing part of it, otherwise the texture of the cloth inight be injured.

This, however, is not the most common method of dyeing by indigo. The usual method is to deprive the indigo of the oxygen which has been combined with the green fecula, and to which it owes its blue colour, and thus reduce to the green state again. It is then capable of being dissolved in water by means of the alcalies or alcaline earths, which act upon

it very readily in that state, To dye wool blue, indigo is mixed with wood, bran, and madder, vegetable substances which readily undergo fermentation ; and the whole is boiled together, stirring the mixture frequently. By this a fermentation takes place, and the oxygen is separated from the indigo. Quick lime or

. alcali is then thrown in, which dissolves the green base of the indigo. The solution of indigo is apt to run into the putrid fermentation, which is known by the putrid vapours which it exhales ; the green colour then disappears, and, indeed, the colouring matter is decomposed. This danger is prevented by adding more lime to correct the putrescent tendency. Sometimes the fermentation does not proceed with sufficient activity, and then more bran

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