COLOURING MATTEES IN WINE. 211 



the pale yellow colour of the liquid which flowed from 

 the precipitate with sugar of lead, may be precipitated 

 by means of basic acetate of lead ; that if this precipi- 

 tate be suspended in water, and sulphuretted hydrogen 

 passed through it, a brown substance will be dissolved 

 out from the sulphide of lead, by means of alcohol 

 and tartaric acid, which comports itself in precisely 

 the same manner as that which was deposited in the 

 sulphide of lead previously mentioned. 



The two precipitates of sulphide of lead, when they 

 were afterwards extracted by means of ammonia, 

 yielded nothing more. The apothemata are soluble in 

 alcohol, and such acids as tartaric acid. 



We may remark, as the conclusion of the whole in- 

 vestigation, that no peculiar colouring matter is to be 

 detected in the two liqueur wines mentioned above ; 

 their colours must be ascribed to apothemata, which 

 have been produced from tannic acid and extractive 

 matter, by the action of the air ; that apothema of 

 tannic acid has here lost its distinctive character by 

 the continued action of oxygen, and no longer yields 

 a precipitate when mixed with acid and gelatine. 



Prom white and liqueur wines, I turn to red or 

 reddish, which, whether very dark or bright coloured, 

 differ entirely from such as are called yellow. 



There appear to be some few kinds of grapes which 

 under a purple skin conceal a red juice. I have never 

 seen them, but have found it stated that wine is pre- 

 pared from such grapes without any closer descrip- 



