Important: Safety Warning
This page describes trade processes that use dangerously toxic materials such as cyanide solutions, mercury amalgams, or strong acids. These processes require training, equipment, and precautions far beyond what the text describes.
This information has been left in for historical purposes but should not be acted upon.
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Carmine Purple
The dye recently invented, and known as carmine purple, is obtained by the solution of uric acid in nitric acid, care being taken to prevent boiling over and too great an increase of temperature. The mixture should remain standing quietly for some days, after which a thick, pasty, or doughy substance is obtained, which is to be treated with warm water, filtered, and the residuum again treated with warm water.
The filtered liquid possesses a reddish or yellowish color, resulting from the organic substances decomposed by the nitric acid. It is next to be evaporated in a large enameled iron vessel, but not heated to the boiling point, which would destroy the murexido (carmine purple) produced. After the liquid has been evaporated to a syrupy consistency, and has assumed a beautiful brownish-red or violet color, it is to be allowed to cool. The entire quantity of the liquid should never be evaporated at one time, nor heated to the boil-