196 TANNIC ACID IN WINE. 



effect of apothema of tannic acid, small quantities of 

 which are soluble in weak spirit. 



2>. That excepting a trace of yellow-coloured sub- 

 stance, no peculiar yellow substance is to be found in 

 Port wine, nothing, that is, which could proceed from 

 the grape skins. 



c. That therefore no peculiar yellow colouring matter 

 need be sought for in red wine which has been cellared, 

 since tannic acid is found in all wines, which neces- 

 sarily becomes apothema, and this apothema must 

 colour the old wine. 



d. That in this manner the old Trench wines becom- 

 ing yellow is sufficiently explained. 



e. That the liqueur wines, which originally contain 

 but little tannic acid, and cannot therefore form a preci- 

 pitate, nevertheless become yellow in the course of 

 time, and this change in their colour may, perhaps, be 

 accounted for in the same way, namely, by the forma- 

 tion of a small quantity of apothema of tannic acid, 



/. That only such wines as are produced from dark 

 purple grapes (which contain a great deal of tannic 

 acid), the skins of which were allowed to ferment, and 

 which therefore contain tannic acid in excess, can form 

 cakes of sediment, when the fermentation is com- 

 pleted. 



g. That this cake-like sediment is apothema of 

 tannic acid, the excess of which could not be dissolved 

 in the wine ; and this was formed from the tannic acid 

 by the oxygen of the air. 



