230 coLouBitfa MATTEKS inr WINE. 



undergo alteration may be proved in other ways. 

 First, by the fact, that the removal of tannic acid 

 by means of albumen, or isinglass, causes colouring 

 matter to be deposited, as in younger wines ; that is, 

 that colouring matter which does not combine with 

 either albumen or isinglass. But a still better ex- 

 ample may be given. Henry has observed that the 

 colour of red wine may be altered by quinine. Qui- 

 nine combines with the tannic acid of the wine, and 

 forms an insoluble salt, which precipitates the colour- 

 ing matter with it. 



It cannot be doubted that colouring matter and 

 tannic acid are combined in the wine. Colouring 

 matter combines with acids, and certainly with tannic 

 acid also. It is undetermined how far this results 

 from the chemical combination of quinine and tannic 

 acid, and how far it is the consequence of the so- 

 called surface attraction. But the experiment with 

 quinine as explanatory of the change produced in the 

 colour of Port wine, in consequence of the formation 

 of apothema of tannic acid by which the colouring 

 matter is withdrawn from the wine, is of sufficient 

 importance to deserve our attention. Red wine needs 

 only to have powdered quinine mixed with it, in order 

 to become perceptibly discoloured, and to deposit a 

 precipitate in which both blue colouring matter and 

 tannate of quinine are found. 



Two circumstances must, however, here be con- 

 sidered. "Wine which has been much discoloured by 



