2677. To Make Carmine by the Langlois Process

2677. To Make Carmine by the Langlois Process. Boiling river water, 4 gallons; cochineal in powder, 1 pound; boil for 10 minutes, then add £ ounce carbonate soda, dissolved in 1 pound water; boil again for 1/2 an hour; cool, add 3/4 ounce alum in fine powder, agitato rapidly until it be dissolved, then let it stand for 20 minutes, after which carefully decant into another vessel. The white of 2 eggs, dissolved in 1 pint water, is now to be added, and the whole well agitated; apply heat until the liquor be clarified, then draw it off, and allow it to repose for 1/2 an hour, or longer, when the clear portion must be decanted, and the carmine that has been deposited at the bottom collected, and placed upon a filter to drain. When it has acquired the consistence of a paste, remove it from the filter with an ivory or silver knife, and finish the drying upon shallow plates, covered with silver paper.

2678. To Make Carmine by Cenette's Process

2678.    To Make Carmine by Cenette's Process. The following is the method employed by Madame Cenette: Finest cochineal, reduced to powder, 2 pounds; pure river water, boiling hot, 15 gallons; boil for 2 hours, then add refined saltpetre, bruised, 3 ounces; boil for 3 minutes longer, and add 4 ounces of salts of sorrel (binoxalate of potassa). Boil for 10 minutes longer, then remove the heat, and allow the liquor to settle for 4 hours, when it must be decanted with a syphon into shallow plates, and set aside for 3 weeks. At the end of this time, the film of mould formed on the surface must be dexterously and carefully removed, without breaking it or disturbing the liquid portion. The latter must be now removed with a syphon, and the remaining moisture drained off, or sucked up with a pipette. The carmine which is left behind must be dried in the shade, and will be found to possess extraordinary lustre and beauty.

2679. To Revive or Brighten Carmine

2679.     To Revive or Brighten Carmine. We may brighten ordinary carmine and obtain a very fine and clear pigment, by dissolving it in water of ammonia. For this purpose leave ammonia upon carmine in the heat of the sun till its color is extracted and the liquor has got a fine red tinge. It must then be drawn off and precipitated by acetic acid and alcohol, next washed with alcohol, and dried. Liquid carmine is a solution of carmine in ammonia.

2680. Adulteration of Cochineal

2680. Adulteration of Cochineal. Genuine cochineal has a specific gravity of 1.25; it is commonly increased in 'weight by slightly moistening it with gum water, and then rouncing it in a bag, first with sulphate of baryta, and then with finely powdered bone-black. In this way its specific gravity is raised to 1.35, by introducing about 12 per cent, of useless matter.

2681. Kirchoff's Method, of Making Vermilion

2681.    Kirchoff's Method, of Making Vermilion. This is said to yield vermilion equal to the Chinese. Rub in a porcelain dish 100 parts mercury with 23 parts flowers of sulphur, moistening the mixture with a solotion of caustic potash. Next treat it with 53 parts hydrate of potash, mixed with an equal weight of water; warm it up and triturate it again. The water must be replaced as it evaporates, and the operation continued for 2 hours. The whole is now to be evaporated to a thin paste, during constant trituration, and the heat removed the moment the color is of a good tint. Even a few seconds too much or too little will injure the result. When cold, the mass is washed with a solution of potash, and afterwards with pure water, and finally dried.