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Prussian Blue (Percyanide when it must be)

Percyanide, when it must be decanted with a syphon into ferrocyanide, or ferroprussiate of iron. Com- shallow plates, and set aside for 3 weeks. At mercial Prussian blue is made by adding to a the end of this time, the film of mould formed solution of prussiate of potash (or of prussiate on the surface must be dexterously and carecake), a solution of 2 parts alum and 1 part fully removed, without breaking it or disturbsulphate of iron, washing the precipitate re-ing the liquid portion. The latter must be peatedly with water to which a little muriatic now removed with a syphon, and the remainacid has been added, and exposing it to the ing moisture drained off, or sucked up with air till it assumes a deep blue color. A purer a pipette. The carmine which is left behind kind is made by adding a solution of persul- must be dried in the shade, and will be found phate or perchloride of iron to a solution of to possess extraordinary lustre and beauty. pure ferroprussiate of potash. (See No. 2679. To Revive or Brighten Car- 2674.) mine. We may brighten ordinary carmine

2676. Action of Prussic Acid on Iron and obtain a very fine and clear pigment, by Solutions. The Germans call prussic acid dissolving it in water of ammonia. For this blausäure, because it produces a blue precipit- purpose leave ammonia upon carmine in the ate in certain iron solutions; but the following heat of the sun till its color is extracted and experiment undoubtedly proves that the prus- the liquor has got a fine red tinge. It must sic acid does not produce the color of that then be drawn off and precipitated by acetic precipitate, since it can be made just as well acid and alcohol, next washed with alcohol, without it. Prepare a saturated solution of and dried. Liquid carmine is a solution of green vitriol in water. Take parts of the carmine in ammonia.