208 COLOURING MATTERS IN WINE. 



taining more or less sugar; and lastly, by a differ- 

 ence in the quantity of apothema existing in such 

 wines. Those wines which eventually become darkest, 

 had originally most tannic acid and extractive matter, 

 and as a rule were rich in sugar and gum. This 

 apothema dissolves as well in water as in alcohol, and 

 if sugar does not promote its solution, it does its mix- 

 ing with the liquid in the form of particles which 

 cannot be looked upon as dissolved ; and gum, in par- 

 ticular, produces this effect. The grape juice from 

 which Teneriffe, Madeira, Muscadel, and such like 

 wines are produced, is colourless, just as Cognac is 

 when put into casks ; no peculiar colouring matter is 

 contained in it, and the causes mentioned concur in 

 producing in it, after a time, a colour resembling that 

 of Madeira and other wines of the same sort. 



Several phenomena indicate apothema of tannic 

 acid as the principal source of the yellow colour of 

 white wines. In the first place, if they are prepared 

 from white grapes, the shorter the time during which 

 the juice and the skins are allowed to be in contact 

 whilst undergoing pressing (the tannic acid is con- 

 tained in the skins, not in the juice), the more 

 colourless will be the wine. And besides this, the 

 wine does not remain white, unless the new oak casks 

 (which contain tannic acid) have been carefully 

 washed, for the tannic acid contained in the 

 cask passes into the wine and is dissolved (p. 118). 

 But since it is impossible to prepare white wine, in 



