§ 142. WINE. 279 



/. Alcoholt —Estimate this in 10 or 25 c.c. of the wine, 

 adding a few drops of soda, or enough to change the 

 color of the wine completely, and about 0.06 grm. of 

 tannin ; the soda neutralizes the free acid, and the tannic 

 acid prevents frothing. For the manner of conducting 

 the distillation, see § 87. 



g. Sugar. — This may be determined in 100 grms. of 

 the wine directly, in the usual manner (§ 81), after decol- 

 orizing the liquid by contact with 2-3 grms. of bone-black, 

 and filtering. 



Or, the wine may be decolorized in this manner 

 (Griffin). Dilute the red wine to about half the extent 

 required for the determination of srtgar, add enough milk 

 of lime to make the liquid alkaline, and agitate the mix- 

 ture Avell ; then add about one-tenth as much of a solution 

 of basic plumbic acetate as was taken of the wine, and 

 shake the mixture again ; finally add one-third as much 

 of a solution of alum, containing 1 part of salt in 20 of 

 Avater, as was required of the j^lumbic solution, dilute the 

 mixture to any volume easily divisible into aliquot parts, 

 mix the whole together by violent agitation, let it stand 

 until the solid matters settle, and then decant enough of 

 the supernatant liquid into a dry filter for the determina- 

 tion of the sugar. 



If the wine is a light-colored one, nothing need be 

 added but sodic carbonate until it is alkaline. 



Cane sugar exists in wine only when it has been pur- 

 posely added. It can be estimated, if present, in the 

 usual way (§ 83). 



If the wine is neutralized with lime, and alcohol added 

 to precipitate malic and succinic acids, a little baryta- 

 water will give a precipitate in the filtrate, which is more 

 or less abundant, according to the amount of sugar pres- 

 ent (§ 83). 



A. Gum (and sugar), etc. — Evaporate 100 grms. of the 

 wine to a syrup on the water-bath, exhaust the residue 



