54 COMPOSITION OF AMERICAN WINES. 



If it is desirable to determine the purity of a wine of unknown origin, 

 a search should also be made for preservatives and foreign coloring 

 matter. 



ESTIMATION OF SPECIFIC GRAVITY. 



The specific gravity of wine is determined at the temperature of 

 15.6 by means of the picnometer, small accurately graduated hydrom- 

 eter, Westphal balance, or a Westphal plummet on the analytical bal- 

 ance. If either of the last three forms of apparatus is employed, the 

 apparent specific gravity of dry wines may be corrected to 15.6 from 

 Table III. The small amount of extract does not materially influence 

 the index of expansion. By this means the specific gravity may be 

 determined with considerable accuracy at the temperature of 25 to 

 30. The error is lessened, however, as the temperature of 15.6 is 

 approached. With sweet wines, however, the temperature should not 

 vary materially from 15.6. 



ESTIMATION OF ALCOHOL. 



One hundred cc of the liquid are measured into an Erlenmeyer flask 

 of from 250 to 300 cc capacity, 50 cc of water are added, the flask is 

 attached to a vertical condenser by means of a bent tube, and 100 cc 

 are distilled. Where occasional determinations of alcohol are made, 

 it is found convenient to use an alembic Saleron. This apparatus is 

 made of copper, and can be readily taken apart and placed in a small 

 box. No rubber connections are necessary, so that the setting up 

 only requires a few minutes. The specific gravity of the distillate is 

 determined as given under specific gravity, and the corresponding 

 percentage of alcohol by volume and grams per 100 cc is obtained 

 from Table 1. 



ESTIMATION OF GLYCEROL. 



One hundred cc of wine are evaporated in a porcelain dish on the 

 water bath to a volume of about 10 cc and the residue is treated with 

 about one gram of quartz sand and with from 1.5 to 2 grams of milk 

 of lime (containing 40 per cent Ca(OH) 2 ) for each gram of extract pres- 

 ent, and evaporated almost to dryness. The moist residue is treated 

 with 5 cc of alcohol (96 per cent by volume), the substance adhering to 

 the sides of the dish being removed with a spatula, and the whole mass 

 rubbed to a paste, with the addition of a little more alcohol. The 

 mixture is then heated on the water bath, with constant stirring, to 

 incipient boiling and the liquid decanted into a flask graduated at 100 

 and 110 cc. The residue is washed repeatedly with 10 cc portions of 

 hot 96 per cent alcohol. The contents of the flask are then cooled to 

 15, diluted to the 100 cc mark with 96 per cent alcohol, and filtered 

 through a folded filter. Fifty cc of the filtrate are evaporated to a 

 sirupy consistency in a porcelain dish, on a hot, but not boiling, water 



