236 METHODS OF ANALYSIS [Chap. 



GLYCEROL IN DRY WINES. 



7 Method I. (By Direct Weighing) — Tentative. 



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

 of about 10 cc. and treat the residue with about 5 grams of fine sand and 4-5 cc. of 

 milk of lime (containing about 15% of calcium oxid) for each gram of extract pres- 

 ent and evaporate almost to dryness. Treat the moist residue with 50 cc. of 90% 

 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 a water bath, 

 with constant stirring, to incipient boihng and decant the Uquid through a filter 

 into a small flask. Wash the residue repeatedly by decantation with 10 cc. portions 

 of hot 90% alcohol until the filtrate amounts to about 150 cc. Evaporate the filtrate 

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

 transfer the residue to a small, glass-stoppered, graduated cylinder with 20 cc. of 

 absolute alcohol and add 3 portions of 10 cc. each of anhydrous ether, shaking 

 thoroughly after each addition. Let stand until clear, then pour off through a 

 filter, and wash the cylinder and filter with a mixture of 1 part of absolute alcohol 

 to 1| parts of anhydrous ether, also pouring the wash liquor through the filter. 

 Evaporate the filtrate to a sirupy consistency, dry for an hour at the temperature 

 of boiling water, weigh, ignite and weigh again. The loss on ignition gives the 

 weight of glycerol. 



8 Method II. (By Oxidation with Bichromate) — Tentative. 



Evaporate 100 cc. of the wine in a porcelain dish on a water bath, the temperature 

 of which is maintained at 85°-90°C., to a volume of 10 cc. and treat the residue with 

 about 5 grams of fine sand and 5 cc. of milk of lime (containing the equivalent of 

 15 grams of calcium oxid). Proceed from this point as directed under XIX, 6, be- 

 ginning with the clause "evaporate almost to dryness, with frequent stirring". 

 Observe the precautions given concerning the temperature at which all evapora- 

 tions are to be made. 



9 GLYCEROL IN SWEET WINES.— TENTATIVE. 



With wines whose extract exceeds 5 grams per 100 cc, heat 100 cc. to boiling in 

 a flask and treat with successive small portions of milk of lime until the wine be- 

 comes first darker and then lighter in color. Cool, add 200 cc. of 95% alcohol by 

 volume, allow the precipitate to subside, filter and wash with 95% alcohol. Treat 

 the combined filtrate and washings as directed in 7 or 8. 



10 GLYCEROL-ALCOHOL RATIO.— TENTATIVE. 



Express this ratio as x : 100, in which x is obtained by multiplying the percentage 

 by weight of glycerol by 100 and dividing the result by the percentage of alcohol 

 by weight. 



EXTRACT. 



11 From the Specific Gravity of the Dealcoholized Wine.— Tentatife. 



Calculate the specific gravity of the dealcoholized wine by the following formula: 



S = G-1-1 — Ain which 



S = specific gravity of the dealcoholized wine; 

 G = specific gravity of the wine, 3; and 



A = specific gravity of the distillate obtained in the determination of alco- 

 hol, 4 (a). 



