COLOTJBING MATTEES IN WINE. 229 



ter, by means of alcohol and tartaric acid, can be 

 extracted from the tartrate of lime, which remains 

 undissolved. 



The scaly precipitate from Port wine, extracted with 

 warm alcohol and tartaric acid, gives a yellow tincture 

 like very old Port wine. If this tincture be treated 

 with chalk, boiling produces no brown solution, the 

 apothema has become insoluble, as is the case with 

 humic acid and humin ; the latter is insoluble in 

 water, and the former sparingly soluble. If the sul- 

 phide of lead (from the precipitate obtained from Port 

 wine by means of sugar of lead) be treated with warm 

 water, the apothema of tannic acid is dissolved out, 

 and if the sulphide of lead be then extracted with 

 alcohol and tartaric acid, the colouring matter of the 

 wine is dissolved in it with a red, but not a Port wine 

 colour. But if obtained from old Port wine, the 

 amount is very insignificant : the younger the wine 

 is the more red colouring matter it yields. 



Doubts might justly be raised as to whether the alte- 

 ration in colour undergone by Port wine and other 

 heavily-loaded wine, is entirely the result of the 

 oxidation of tannic acid and extractive matter, and of 

 the precipitation of blue colouring matter, which is 

 carried away with the apothema, which has become 

 insoluble. Pure blue colouring matter may, however, 

 be prepared from the precipitate in Port wine, which 

 does not by precipitation suffer alteration. 



That the colouring matter does not necessarily 



