214 COLOURING MATTERS IN WINE. 



purple grapes, which are rich in albumen and sugar, 

 impart a darker colour to the wine. As a rule, young 

 dark-coloured wines are stronger than others. The 

 darker they are the more tannic acid was originally 

 contained in them; and these are the wines which 

 become yellow in course of time, and lose almost all 

 their tannic acid by the formation of apothema, which 

 withdraws the colouring matter from the liquid. This 

 is the case with Port wine, whilst in many French 

 wines relatively more colouring matter than tannic 

 acid is contained, in consequence of which, though 

 they give rise to apothema, yet they never become 

 yellow without retaining a considerable tinge of 

 bluish red colour. 



The colour must also necessarily be affected by the 

 amount of acid, be it free tartaric, or acetic contained 

 in the wine. The wine will be redder the more 

 free acid it contains ; the brighter it is the less 

 yellow, and the less apothema is formed and exists 

 in solution. A perceptible difference in colour is 

 likewise occasioned by a small difference in the 

 amount of cream of tartar contained in the wine. 

 But the difference of colour does not depend entirely 

 upon these causes. The amount of colouring matter 

 and of tannic acid differs even in purple grape skins ; 

 some are so dark as to be nearly black, others again 

 are light purple, and of course light and dark wines 

 will be respectively produced. 



Lastly, the skins may be left for a longer or shorter 



