Arnotto Yellow on Cotton.

Practical Magazine 17, 1876

(Chemistry applied to the Arts, Manufactures, &c.
Dyeing, Calico Printing, Bleaching, Tanning, and Allied Subjects.)

Arnotto is one of the few colouring matters which can be applied to cotton fibre directly without a mordant, and which are extensively used for cotton printing and dyeing in general. The ordinary methods of applying it are attended with some uncertainty and inconvenience. Sometimes the yellow is too bright or too deep, sometimes pure yellow or reddish yellow, and moreover, the colour will not always stand well.

M. KIELMEYER has observed that a mixture of alcohol and a soda lye dissolves the yellow and red ingredients of arnotto much more completely than either of these solvents alone. Hence he has sought and found a new formula for the yellow of arnotto, which practice has confirmed. It requires only half the lye necessary with other formulae, while it ensures the duration and permanence of the printed colour by reducing to a minimum the injurious influence on the browns and reds, and by brightening the yellow colour.

He puts 66 lbs. of arnotto in 5¼ galls. of alcohol, and adds to it, while continually stirring, 2½ galls. of a soda lye of 1,598 spesific gravity. The whole having a temperature of 113° to 122°F., is left for a night in a copper boiler. The liquid is then drawn off, and the undissolved residuum is collected on a metallic sieve, carefully pressed, and treated with 7¾ galls. of boiling water to free it from all solution of arnotto mechanically adhering to it. The watery bright yellow solution, after having cooled, is added to the preceding alcoholic solution, and the whole is thickened with 13 lbs. of gum tragacanth mucilage.

The shade which is obtained on cotton with this printing co lour, after evaporation and washing, is a very intense orange yellow, which is not dear, for notwithstanding the use of alcohol, the colour costs less than that prepared by the ordinary formulae, because it admits of much less arnotto, which is a direct proof that by this treatment of arnotto there is less reason to fear loss of colour by decomposition.

If a brighter shade is desired, with less orange in it and more approaching canary yellow, as for very thin pocket handker chiefs, aluminate of soda and a decoction of yellow berries are to be added to the diluted colour. The ammoniacal solution of turmeric is not to be recommended, because it cannot be kept in any quantity for more than two or three hours.

- Polytechnisches journal.

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