Aniline Black.

Scientific American 23, 5.6.1869

Cotton And Silk Dyeing.
According to Mr. Cam. Koechlin, these fibers may be dyed in a solution made of - water, 20 to 30 parts; chlorate of potassa, 1 part; sal ammoniac, 1 part; chloride of copper, 1 part; Aniline, 1 part, and hydrochloric acid, 1 part, previously mixed together.
The fabric or yarn is dried in ageing rooms at a low temperature for 24 hours, and washed afterwards.

Wool Dyeing or Printing.
Mr. J. Lightfoot prepared the wool by a kind of oxidation made as follows: 1 part of bleaching powder is diffolved in 10 parts of water. Then for 1 pound of wool, take about a pint of the above solution, dilute it with siz gallons of water, and add 3 ozs. ofr muriatic acid. In this bath, which is at the temperature of 100° Fah., work the wool during 20 or 30 minutes, and until it has acquired a yellowish tint. Then wash it thoroughly and let it dry.
Wool and mixed fabrics thus prepared may be dyed and printed in the usual way.

Silk Printing.
In this case silk is to be vegetablized (we have already the word animalized) by an immersion in a bath of cellulose dissolved in ammoniacal copper oxide. We think this process quite delicate, on account of the action of ammonia on the silk.

Calico Printing.
The first application of aniline black to calico printing was made by Mr. John Lightfoot. One of the early printing mixtures was made of - Water 5½ qts.; white starch, 1 lb. 14 ozs.; chlorate of potassa, 6 ozs.; hyrochloriate of aniline, 1 lb.; sulphate or chloride of copper, 5.ozs.

The aniline black obtained was very fine and fast; but the great quantity of copper salt employed was found to be injurious both to the fabric and to the metallic printing rollers.

Subsequent experiments made by Messes. C. Koechlin, Cordillor, and Lauth, have led to the substitution of sulphide of copper for the sulphate and chloride of this metal, whose presence seems indispensable to the production of aniline black. A good printing paste, which does not weaken the fabrics and does not corrode the scrapers and the rollers of the printing apparatus, is made as follors:

Host and digest - water, 1 lb.; starch, 2 lbs.; sulphide of copper, 8 ozs. On the other hand, mix and heat - torrefled starch, 2 lbs. 6 ozs. water 4lbs.; gum tragacanth water, 1qt.; hydrochlorate of aniline, 1 lb. 9½ ozs.; sal ammoniac, 3½ ozs.; chlorate of potassa, 9½ ozs. Then mix the two compositions, print, and expose the fabric in the ageing room for 24 hours, and at a temperature from 77° to 104° Fah.

Here is another paste by Mr. Käppelin: Starch paste, 2 1/5 gals., chlorate of potassa, 7pz.; gum tragacanth water 5½ lbs.; sulphide of copper 14 ozs.; sal ammoniac, 9ozs.; a salt of aniline (tartrate) 2 1/5 lbs., which is added last.

Tartrate of aniline does not corrode the steel scrapers,a nd is gradually transformed into hydrochlorate of aniline by the sal ammoniac of the mixture. Nitrate and hydrochlorate of aniline are the only salts of aniline which can produce the black.

After 24 hours' standing in the ageing room, the prints are drawn through a bath containing 2 per cent of carbonate of soda, steamed, and washed.

Acids will turn the color to green, but alkalies will restore the black. A solution of bichromate of potassa intensifies the color; but an excess of this salt is apt to impart a reddish hue.

The best aniline for black is the one which contains a mixture of aniline and toluidine, and which is sought for in the manufacture of reds.

The sulphide of copper is made by dissolving the ordinary temperature 2 parts of sublimed sulphur in 2 parts of caustic soda, at 38° Baumé. After 24 hours' standing and frequent stirrings, the solution is complete, and is thrown into a warm solution of 10 parts of sulphate of copper in 250 parts of water. The precipitate is washed and drained until about 10 pints are obtained, each pint therefore corresponds to 1 pound of sulphate of copper.

Lucas paste. - It contains acetate of copper and hydrochlorate of aniline, without sal-ammoniac, an has been submitted to a peculiar process. When used, this paste, mixed with 6 to 8 times its volume of starch paste. The temperature of the ageing room is about 104° Fah.

Paraf's paste. - It is a mixture of hydrochlorate of aniline, chlorate of potassa, hydrofluosilicic acid, and a thickening. It produces a very fine black when applied with copper or brass rollers, which furnish the copper necessary to the development of the color. If no copper is present, the shade is only a dirty blue. All these aniline blacks are remarkable as being very fast, unalterable by acids or alkalies, and even by chlorine to a certain point. If chlorine is not used in great excess, the black color will reappear; if in excess, the color remains fallow. Aniline black may also be printed simultaneously with madder and most steam colors.

All the compositions for producing aniline black must be acid, and the more acid there is, the more rapid is the production of the black. We ought, however, to remain within proper limits, otherwise the fiber may be weakened.

The degree of acidity of the paste will also vary with the thickenings employed. Gum senegal requires more acidity than torrefied starch, and the latter more so than white starch or gum tragacanth.

In printing aniline black care should be taken not to print upon, or too near other places previously mordanted; the mordant would be acted upon, and if it contains acetic acid, this acid once liberated would prevent the formation of black, which will be only gray.

There is also danger of spontaneous combustion, so rapid is the oxidation going on, when the printed piece is allowed to remain folded and wet. It should be immediately spread out in the ageing room. - Dictionary of Dyeing and Calico Printing.

Ei kommentteja :