CHAPTER XXI. 



SUGAR IN WINE. 



Two methods have been adopted for determining the 

 saccharine contents of wine ; the wine has either been 

 freed from alcohol by evaporation, ferment added to 

 the residue, and the amount of sugar calculated 

 from the loss of carbonic acid during fermentation 

 (Tresenius), or it is treated in the manner already pre- 

 scribed for determining grape sugar, by a standard solu- 

 tion of salt of oxide of copper. Fehling, who has 

 repeatedly tried this latter method, remarks, that it 

 gives from J to i per cent, too much sugar, since there 

 are other substances besides sugar in wine, which re- 

 duce the oxide of copper to a sub-oxide. I never 

 directly examined the saccharine contents of wine, as 

 they have been sufficiently analysed by others ; who, 

 however, using a solution of copper, always obtained 

 a constant error to the amount just mentioned (since 

 there are bodies in wines besides sugar, which reduce 

 oxide of copper to sub-oxide) ; and by the method of 

 fermentation a mistake of 4 per cent, may be caused, 

 as is mentioned by Thenard (p. 251). 



Besides this, the saccharine contents of wine may 

 be approximative^ estimated from the wine extract. 



