730 CARMINE 



thrown in, and the decoction is stirred : it changes colour immediately and inclines 

 to a more brilliant tint. At the end of fifteen minutes the cochineal is deposited at 

 the bottom, and the bath becomes as clear as if it had been filtered. It contains the 

 colouring matter, and probably a little alum in suspension. It is then decanted into 

 a copper of equal capacity, and placed over the fire, adding the fish-glue dissolved 

 in a great deal of water, and passed through a searce. At the moment of ebullition, 

 the carmine is perceived to rise up to the surface of the bath, and a coagulum is 

 formed, like what takes place in clarifications with whites of egg. The copper must 

 be immediately taken from the fire, and its contents be stirred with a spatula. In the 

 course of fifteen or twenty minutes the carmine is deposited. The supernatant 

 liquor is decanted, and the deposit must be drained upon a filter of fine canvas or 

 linen. If the operation has been well conducted, the carmine when dry crushes 

 readily under the fingers. What remains after the precipitation of the canninu is still 

 much loaded with colour, and may bo employed very advantageously for carminated 

 lakes. See LAKE. 



There are sold at the shops different kinds of carmine, distinguished by numbers, and 

 possessed of a corresponding value. The difference depends upon two causes, either 

 upon the proportion of alumina added in the precipitation, or of a certain quantity of 

 vermilion put in to dilute the colour. In the first case the shade is paler, in the 

 second it has not the same lustre. It is always easy to discover the proportion of the 

 adulteration. By availing ourselves of the property of pure carmine to dissolve in 

 water of ammonia, the whole foreign matter remains untouched, and we may estimate 

 its amount by drying the residuum. 



Carmine is, according to Pelletier and Caventou, a triple compound of the colour- 

 ing substance and an animal matter contained in cochineal, combined with an acid 

 added to effect the precipitation. The most successful investigator into the colouring 

 matter of the cochineal has been Mr. Warren Do La Hue. This chemist had the 

 opportunity of submitting the living insect to microscopical examination. He found 

 it to be covered with a white dust, which was likewise observed on the adjacent parts 

 of the cactus leaves on which the animal feeds. This dust, which he considered to be 

 the excrement of the animal, has, under the microscope, the appearance of white 

 curved cylinders of a very uniform* diameter. On removing the powder with ether, 

 and piercing the side of the insect, a purplish-red fluid exudes, which contains red 

 colouring matter, in minute granules assembled round a colourless nucleus. These 

 groups seem to float in a colourless fluid, which appears to prove, that whatever may 

 be the function of the colouring matter, it has a distinct and marked form, and does 

 not pervade, as a mere tint, the fluid portion of the insect. To this colouring matter, 

 Mr. De La Rue has given the name of CARMINIC ACID. 



It has been shown by Schutzenberger that the carminic acid in carmine is combined 

 with a nitrogenous base called tyrosine. 



There are some remarkable peculiarities about the production of carmine. The shade 

 and character of the colour are altered by slight, very slight, differences of the tem- 

 perature at which it is prepared ; and with every variation in the circumstance of 

 illumination, a change is discovered in the colour. Sir H. Davy relates the following 

 anecdote in illustration of this : 



' A manufacturer of carmine, who was aware of the superiority of the French 

 colour, went to Lyons for the purpose of improving his process, and bargained witli a 

 celebrated manufacturer in that city for the acquisition of his secret, for which he was 

 t.o pay 1,000. He saw all the process, and a beautiful colour was produced, but he 

 found not the least difference in the French method and that which had been adopted 

 by himself. He appealed to his instructor, and insisted that he must have kept some- 

 thing concealed. The man assured him that he had not, and invited him to inspect 

 the process a second time. He very minutely examined the water and the materials, 

 which were in every respect similar to his own, and then, very much surprised, he 

 said : " I have both lost my money and my labour ; for the air of England does not 

 admit of our making good carmine." " Stay," said the Frenchman, " don't deceive 

 yourself; what kind of weather is it now?" "A* bright sunny day," replied the 

 Englishman. " And such are the days," replied the Frenchman, " upon which I make 

 my colour : were I to attempt to manufacture it on a dark and cloudy day, my results 

 would be the same as yours. Let me advise you to make your carmine on sunny 

 days." ' Experiments on this subject have proved that coloured precipitates which 

 are brilliant and beautiful when they are precipitated in bright sunshine, are dull, 

 and suffer in their general character, if precipitated in an obscure apartment, or in 

 the dark. 



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 

 we leave ammonia upon carmine in the heat of the sun, till its colour is extracted, 



