206 COLOTJBING MATTEES IN WINE. 



the tannic acid of wine to apothema as shall insure 

 the wine's becoming darker, for, indeed, only a very 

 small quantity of oxygen is necessary to effect this. 

 The effect is produced very slowly, and so the wine 

 only seems to darken year by year. The insignificant 

 quantity of tannic acid contained originally in the 

 wine decreases in the same proportion, and at last 

 disappears entirely. 



In some wines the alteration in colour is very 

 speedily effected. Trommsdorff * gives us instances of 

 white Bordeaux and Rhine wines, whose colour when 

 exposed to the air quickly became so dark as to rival 

 that of Malaga. The French wines in which he per- 

 ceived this occur were Haut, Brassac, and Haut Sau- 

 terne, but he once saw the same thing in Liebfranen- 

 niilch, the colour of which in a very short time nearly 

 equalled that of old Jurancon. He thought he should 

 find more tannic acid in the wine, but of course he 

 did not, for if the colour was really produced from 

 apothema of tannic acid, precisely the same amount 

 of tannic acid must have disappeared. 



We are not quite in the dark as to the causes of 

 this phenomenon. The wines which Trommsdorff men- 

 tions had been protected from the air, and when again 

 exposed to it very quickly became dark. We can- 

 not doubt that in this case tannic acid was resolved 

 into apothema, But the question is, why this change 

 was not effected until the wine was exposed to the 



* Neues Journal der Pharm. Bd. 24, St. 2, S. 119. 



