COLOUBINa MATTEES IN WINE. 221 



have become turned, are darker coloured, and why a 

 copious addition of potash or lime, completely destroys 

 the colour of wine (p. 125). 



Though the colouring matter is thus easily affected 

 by alkalies, it is proportionably insensible to strong 

 acids. If oil of vitriol be dropped into its solution in 

 alcohol, and tartaric acid, the colour becomes bright 

 and strong red ; excess renders the colour rather violet, 

 but dilution with water restores the pure red. 



Nitric acid when not too strong renders the colour 

 brighter, but heat decomposes it. 



If chlorine water be carefully dropped into the 

 solution it loses its colour and becomes brown. In 

 this new form it is to a certain extent constant, for 

 even if no more chlorine water be added, the brown 

 colour is retained, whilst in case of a further addi- 

 tion, the brown substance is discoloured, and becomes 

 bright yellow. 



This peculiarity is important, since Faure deduces 

 from it that two colouring matters exist in wine. 



There may be two coloured substances contained in 

 it, red colouring matter and apothema of tannic acid 

 (194). But in preparing the blue colouring matter, 

 the apothema was removed, and the reaction, which 

 Faure ascribes to two colouring matters, proceeds from 

 the pure colouring matter of wine. 



Chlorine acts first upon the red colouring matter in 

 the same manner as alkalies, which cause it to turn 

 brown when exposed to the air. The first operation 



