COLOURING MATTERS IN WINE. 213 



begins, and at a later period increases ; the amount of 

 colouring matter is not thereby diminished, but the 

 larger proportion of acid in the liquid reddens its co- 

 lour. Another period now begins, during which the 

 tannic acid is slowly converted into apothema, whereby 

 red colouring matter is again precipitated out of the 

 liquid, for example in Port wine ; it thus gradually 

 diminishes, and finally, after a length of time, disap- 

 pears entirely from the wine, which then remains 

 what is called yellow. 



The fact that difference of time causes percep- 

 tible variety in the colour of red wines of the same 

 kind, is thus explained by the various circumstances 

 in which the colouring matter finds itself. 



"We are only acquainted with one kind of colour- 

 ing matter, and there is no reason for supposing that 

 more than one kind exists, however great the variety 

 of colour in wines may be. Let us now consider the 

 variety of circumstances which may influence the 

 colour produced by one colouring matter, before we 

 proceed to describe the colouring matter itself. 



If a particular wine obtains by fermentation only 

 10 per cent, alcohol, whilst another rises to 16 

 per cent., then supposing a sufficient quantity of 

 blue colouring matter present in the skins, the 

 latter, as young wine, will be much darker coloured 

 than the former, since colouring matter dissolves 

 far more readily in alcohol and tartaric acid, than 

 in water and tartaric acid. This explains why 



