218 COLOURING MATTERS IK WIFE. 



rated without decomposition, and even at an ordinary 

 temperature the colouring matter of wine cannot bear 

 any excess of alkali, nor even of ammonia, without 

 becoming speedily brown. 



It cannot therefore be isolated in this manner. 



There is only one method by which I have been 

 able to obtain pure blue colouring matter of wine 

 isolated. Sulphide of lead, freed from apothema by 

 means of boiling water, is extracted with alcohol and 

 strong acetic acid. The colouring matter is sufficiently 

 soluble in it, though more sparingly so than in alcohol 

 and tartaric acid. The alcoholic liquid containing 

 acetic acid is then evaporated, when it first becomes 

 red like wine; then, after evaporation, violet; and lastly, 

 if a little acetic acid be present, of a singularly beautiful 

 blue. Pat is at the same time separated. If the 

 liquid be now evaporated to dryness, the fat extracted 

 with ether, and a trace of the oxide of lead with acetic 

 acid, the colouring matter remains perfectly pure. 



The colour is bluish black, like black lead ; I have 

 never been able to obtain it in crystals. It is quite 

 insoluble in alcohol, water, ether, chloroform, sulphide 

 of carbon, olive and turpentine oil. "Whatever has been 

 maintained to the contrary, it is perfectly insoluble in 

 all these liquids. I have already said that it is blue in 

 the solution. Much blue colouring matter, when put 

 into alcohol with a trace of acetic acid, yields a sin- 

 gularly beautiful pure blue liquid; more acetic acid 

 makes it red. "We may become acquainted with this 



