COLOURING MATTEES IN WINE. 199 



As we find among so-called yellow wines a va- 

 riety which extends from such as are almost colour- 

 less to the dark brown, we must endeavour to explain 

 this whole series of varieties and as red wines vary 

 from more or less crimson to the darkest purple red, 

 and yet become yellow in the course of time, it may 

 not be superfluous to d\\ ell a little upon these points. 



Endless variety may result from one and the same 

 cause. Supposing the amount of blue colouring 

 matter reddening by means of acids to exist in equal 

 quantities in all red wines, a variation in the quantity 

 of cream of tartar, or of an acid salt, will still cause a 

 difference in the colour. The addition of a single mil- 

 legramme ('015 gr.) of cream of tartar in a bottle of 

 wine makes it redder, or vice versa, darker. But besides 

 cream of tartar, free tartaric acid is found in many, 

 and malic acid in some wines. In proportion to the 

 amount of free tartaric and malic acid will be the red- 

 ness of the wine. The same holds good with respect 

 to acetic acid which is found in all wines. 



But the quantity of colouring matter is also vari- 

 able ; and in proportion to its excess, an equal amount 

 of acids being assumed, the colour of the wine will be 

 darker, since a fixed quantity of acid is necessary to 

 make the colouring matter of wine red. 



In order to understand this subject clearly, it will 

 be advisable in treating of it to begin with the facts 

 derived from experience, and hence, first, that all red 

 wines, without distinction, owe their colour to one and 



