CARMIN. 159 



It is not altered by exposure to the air, nor does it absorb any 

 sensible quantity of moisture. When heated to 122 it melts. 

 If the heat be increased it swells up, and is decomposed, yielding 

 carburetted hydrogen, a great deal of oil and a little water, hav- 

 ing a slightly acid taste. It gives no trace of ammonia ; yet, 

 according to the analysis of Pelletier and Caventou, azote consti- 

 tutes one of its constituents, though its quantity is small. 



Carmin is very soluble in water. The solution may be con- 

 centrated by evaporation to the consistence of a syrup ; but no 

 crystals are deposited. The aqueous solution has a fine carmine 

 red colour. A very small quantity of carmin communicates its 

 colour to a great deal of water. It is soluble also in alcohol ; 

 but the stronger the alcohol the worse a solvent it becomes. It 

 is insoluble in ether. The weak acids dissolve it, probably in con- 

 sequence of the great quantity of water which they contain. No 

 acid precipitates it when pure ; but they almost all throw it down 

 when it is in combination with the peculiar animal matter of the 

 cochineal. All the acids, however, induce a sensible change upon 

 the aqueous solution of carmin. They cause it, in the first place, 

 to assume a lively red colour, which gradually acquires a yellow- 

 ish tinge, and at last becomes quite yellow. When the acids are 

 not very concentrated, the carmin is not altered in its nature, for 

 when we saturate the acid, the solution assumes its original co- 

 lour. 



Concentrated sulphuric acid destroys and chars carmin. Mu- 

 riatic acid decomposes it without charring, and converts it into 

 a bitter tasted substance, which has no resemblance to the origi- 

 nal colouring matter. Nitric acid decomposes it with still greater 

 rapidity. Some needle-form crystals are formed similar in ap- 

 pearance to oxalic acid ; but they do not precipitate lime-water, 

 even when mixed with ammonia. 



Chlorine acts with energy on carmin, giving it at first a yel- 

 low colour, and afterwards destroying the colour altogether^ 

 Chlorine causes no precipitation in an aqueous solution of carmin^ 

 provided the solution be pure. It is therefore a useful reagent 

 to enable us to discover the presence of an animal matter in the 

 solution of carmin. Iodine acts precisely as chlorine, but with 

 less rapidity. 



The alkalies, when poured into a solution of carmin, give it a 

 violet colour. If the alkali be saturated immediately, the origi- 



