XIII. METHODS FOR THE ANALYSIS OF WINE. 



The determinations of most value in judging the purity of win< an- alcohol, 

 glyeerol, extract, ash. total and volatile acids, and reducing sugar. The actual 

 percentage of these substances present is of interest, but much more important 

 are certain relations between them, such as ash to extract, extract to alcohol, 

 alcohol to glycerol, alcohol to acids, and volatile acids to total acids. Examina- 

 tion for preservatives and foreign coloring matter must also be made. In the 

 examination of sparkling wines, remove carbon dioxid by shaking. 



1. Specific Gravity. Provisional. 



Determine at 15.6 C. by means of a pycnometer, a small accurately graduated 

 hydrometer, or a Westphal plummet on the analytical balance. If a pycnometer 

 be used it should be warmed quickly to room temperature after filling and 

 before weighing, to prevent the error due to the collection of moisture on the 

 outside. A small hole filed in the cap will permit the necessary expansion in 

 the volume of the liquid. 



2. Alcohol. Provisional. 



Measure 100 cc of the liquid at 15.6 C. into a distilling flask of from 250 to 

 300 cc capacity ; add 50 cc of water ; attach the flask to a vertical condenser 

 by means of a bent tube and distil almost 100 cc, making up to 100 cc volume 

 when cooled to 15.6 C. Foaming, which sometimes occurs, especially with 

 new wines, may be prevented by the addition of a small amount of tannin. 

 If it be desired to determine the alcohol in wines which have undergone acetic 

 fermentation and contain a large amount of acetic acid, 0.1 or 0.2 gram of 

 precipitated calcium carbonate should be added. This is unnecessary, however, 

 in wines of normal taste and odor. Determine the specific gravity of the dis- 

 tillate as directed under " 1. Specific Gravity," and obtain the corresponding 

 percentage of alcohol, by volume and grams per 100 cc, from Table II, page 203. 

 Multiply the per cent of alcohol by the weight of the distillate (corresponding 

 to the specific gravity in Table II) and divide the result by the weight of the 

 sample (calculated, from the specific gravity) to obtain the per cent of alcohol 

 by weight. 



3. Glycerol. Provisional, 

 (a) IN DRY WINES. 



Evaporate 100 cc of wine in a porcelain dish on the water bath to a volume 

 of about 10 cc and treat the residue with about 5 grams of fine sand and with 

 from 3 to 4 cc of milk of lime (containing about 15 per cent of calcium oxid) 

 for each gram of extract present, and evaporate almost to dryness. Treat the 

 moist residue with 50 cc of 90 per cent alcohol by volume, remove the substance 

 adhering to the sides of the dish with a spatula, and rub the whole mass to a 

 paste. Heat the mixture on the water bath, with constant stirring, to incipient 



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