236 coLOUBitfa MATTEES IK WINE. 



berries, and, as far as possible, lie excludes the air when 

 examining them. "We have not found the colouring 

 matter of wine variable, at least not when combined 

 with acid. A watery extract of purple grape-skins be- 

 came mouldy after being for a few days exposed to the 

 air, but it still remained pure red. And in all the 

 examinations we instituted a like result was obtained. 

 The colouring matter cannot in the least bear a raised 

 temperature or the action of alkalies. 



I interpolate these remarks for the sake of explain- 

 ing how colouring matter remains unchanged in all 

 wines. It suffers no alteration; it does not origi- 

 nate the sediment which forms in red wine, since it 

 combines and is deposited with another substance, 

 which gradually becomes insoluble. It has the same 

 properties in young and old wine. 



These observations are of value when considering 

 the manner in which the colour of some red French 

 wines become gradually darker in the course of time. 

 If the colouring matter of wine were gradually to 

 change colour, it would be impossible to separate it 

 pure, and this is nevertheless possible. "Wines which 

 become darker, owe the change in colour to the dimi- 

 nution of their acid contents, and the quantity of 

 acetic acid which has been converted into acetic 

 ether, and to the decomposition of tartaric acid or its 

 compounds alterations which we have already con- 

 sidered (p. 110). 



Nothing more clearly proves the durability of the 



