COLOURING MATTERS IN WINE. 207 



air. It is quite certain that these wines had, during 

 their preparation, been very little in contact with 

 air, had been very soon bottled, and had not been fre- 

 quently drawn. If at an earlier period they had been 

 sufficiently exposed to the air, they would gradually 

 have acquired more intensity of colour, and not have 

 altered at once on coining in contact with air. Faure 

 has observed the fact commented upon (p. 118), that 

 so much tannic acid as is necessary to turn wine 

 black when exposed to the air, may be extracted by 

 the wine from the wood of the casks. 



"We have seen, in speaking of Port wine (p. 190), 

 that the oxidizing action of air on the tannic acid 

 of wine is stronger in proportion as the amount of 

 tannic acid exceeds what is commonly met with in 

 liqueur wines. In these latter the resolution of colour- 

 less tannic acid into brown apothema is checked by 

 the sugar. In wine poor in sugar and rich in tannic 

 acid this is quickly chaDged into apothema, the wine 

 becoming deep yellow. In wines which are rich in 

 sugar and poor in alcohol, the production of apothema 

 is slow, since the sugar hinders its formation. 



Xow, if we confine our attention to the variety of 

 colour which may be produced in pure colourless 

 wine, by means of a small portion of a brown sub- 

 stance, we must allow that such variety in the colour 

 may be fully explained, first, by a difference in its 

 solubility in a weaker or stronger alcoholic liquid; 

 secondly, by a difference in its solubility in a liquid con- 



