THE GRAPE. 29 



we examined, a trace of malic, but no citric acid was 

 found. 



Winkler thought he had discovered an acid in the 

 juice of unripe grapes, which he calls "para -citric." 

 But Pasteur* looked upon this as malic acid. 



Until a few years since the opinion was entertained 

 that in the grapes of the Vosges, and exceptionally in 

 a few other kinds, an acid existed, having the same 

 constituents as tartaric acid, but differing from it in 

 its properties. Pasteur, Kestner, and others, have 

 asserted that this, which is called racemic acid, is not 

 so very rare. The last-named found it in insignifi- 

 cant quantities in 1850, in French and Tuscan wine ; 

 by the former it was detected in the tartar of many 

 German wines. Pasteur succeeded in turning tartaric 

 into racemic acid, by warming tartrate of cinchonine, 

 or tartaric ether ; in either case the result is the 

 conversion of tastaric into racemic acid. 



Considering how nearly related acids are to each 

 other, and how possible it is to turn one acid into 

 another, it can astonish no one that racemic acid 

 should be more and more frequently met with in 

 wine. 



The admixture of a small quantity of racemic acid 

 makes no difference whatever in the quality of the 

 wine. And the quality of the wine is only affected 

 by the presence of a large quantity of racemic acid, 

 first, because less lime will then be found in it 



* Journ. de Pliarm. 3 Serie, t. xxiv. p. 75. 



