158 ANIMAL COLOURING MATTERS. 



CHAPTER I. 



OF CARMIN. 



Cochineal ( Coccus cacti) is an insect which inhabits different 

 species of cactus* as the coccinellifer, opuntia, turia, &c. These 

 plants are cultivated in Mexico and some other parts of Ameri- 

 ca for the nourishment of the insect. 



The females are stationary upon the plant. They are collect- 

 ed, killed by heat, and then dried. They occur in commerce in 

 the state of small dark-brown grains ; and are employed in dye- 

 ing scarlet, and in making a beautiful red lake used as a colour 

 by painters. 



Cochineal was first examined by Dr John 1813.f He made 

 a chemical analysis of the insect, extracted the colouring matter, 

 and described its characters under the name of cochenillin. In 

 1818, an elaborate examination of cochineal and of its colouring 

 matter under the name of carmin, was published by Pelletier 

 and Caventou,J and in 1832 the subject was farther prosecuted 

 by Pelletier, who made a chemical analysis of carmin and de- 

 termined its constitution. 



Carmin may be obtained from the cochineal insect in the fol- 

 lowing manner : Digest the cochineal insect in alcohol as long 

 as it communicates a red colour to that liquid. When these so- 

 lutions are left to spontaneous evaporation they let fall a crystal- 

 line matter of a fine red colour. This is carmin, but not in a 

 state of purity. Dissolve these crystals in strong alcohol, and 

 mix the solution with its own bulk of ether. The liquid becomes 

 muddy, and after an interval of some days the carmin is deposit- 

 ed at the bottom of the vessel, forming a beautiful purplish red 

 crust 



Carmin thus obtained has a fine purple red colour. It ad- 

 heres strongly to the sides of J:he vessel in which it is deposited 

 It has a granular appearance, as if it were composed of crystals. 



* A detailed account of this insect, of the wild cactus, and of the mode of 

 rearing these insects, and preparing them for dye stuff, may be found in Ban- 

 croft's Researches concerning the Philosophy of Permanent Colours, i. 236. 



f Chemische Untersuchungen, iii. 210. 



\ Ann. de Chira. et de Phys. viii. 250. Ibid. li. 194, 



