COLOURING MATTERS IN WINE. 233 



m all these liquids. A solution of the yellow colouring 

 matter in ether being at first but slightly coloured, 

 becomes after evaporation, if left to itself, and espe- 

 cially if exposed to the rays of the sun, first rose- 

 coloured, then reddish, and at last violet. 



In proportion as one or other of these colouring 

 matters preponderates, the colour of the wine will 

 vary. Eaure says that he was able to decompose the 

 blue by chlorine without altering the yellow. When 

 tannic acid preponderates over the colouring matter, 

 the wines become discoloured by gelatine ; when the 

 contrary is the case they retain a rose-colour. 



Faure is mistaken respecting the solubility of blue 

 colouring matter in water and alcohol. He probably 

 employed water with the addition of an acid or salt, 

 and it seems that he was not acquainted with colour- 

 ing matter in a pure state. 



The yellow colouring matter which Faure* detected 

 in wine he considers to be a compound of two sub- 

 stances, which he confounds with one another. He 

 first overlooks the apothema which is found in all red 

 wines ; and secondly, is of opinion that the blue 

 colouring matter which, when slightly affected by 

 chlorine becomes brown, is a constituent of wine : it 

 is really the product of oxidation of blue colouring 

 matter (p. 222), which if further decomposed by the 

 addition of more chlorine, becomes pale yellow. This 

 explains how Paure came to imagine that blue colour- 

 ing matter could be decomposed without the yellow 



