Method of recovering Indigo, Cochineal, Madder, and other colouring matter from Wool or Woollen Fabrics.

Practical Magazine 14, 1876

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

The wool or woollen goods containing indigo, cochineal, madder, or other colouring materials, are put into a digester capable of resisting a high pressure, and exposed to the action of steam at a very high pressure, till the whole is entirely dissolved. It requires about six hours for 1,000 kilogrammes (2,205 lbs.) with a pressure of 40 to 50 kilogrammes (88 to 110 lbs.) for every 3 square centimetres (about 4½ square feet). When the solution is complete, water is added and boiled for a few moments, to render the mass more fluid. It is then strained through a coarse filter to separate the foreign substances, and through a second filter to separate the indigo, cochineal, madder, and other colouring matters. These colours are washed with water, again filtered, and dried. The solution which has passed through the filters is used either in the manufacture of prussiate of potash or sulphate of ammoniac, or for artificial manure.

- Moniteur Industriel Belge, Jan. 1st, 1876.

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