84 METHODS OF ANALYSIS. 



boiling and decant the liquid through a filter into a small flask. Wash the 

 residue repeatedly by decantation with 10 cc portions of hot 90 per cent 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 absolute ether, thoroughly shaking 

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

 wash the cylinder and filter with a mixture of one part of absolute alcohol to 

 one and one-half parts of absolute ether, pouring the wash liquor also through 

 the filter. Evaporate the filtrate to a sirupy consistency, dry for one hour at 

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

 ignition gives the weight of glycerol. 



(b) IN SWEET WINES. 



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

 flask the portion to be used in the determination of glycerol, and treat with suc- 

 cessive small portions of milk of lime until it becomes first darker and then 

 lighter in color. When cool add 200 cc of 95 per cent alcohol, allow the precipi- 

 tate to subside, filter, and wash with 95 per cent alcohol. With the filtrates 

 thus obtained proceed as directed under (a). 



4. Glycerol-Alcohol Ratio. Provisional. 



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

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

 by weight of alcohol. 



5. Extract. Provisional. 



(a) FROM SPECIFIC GRAVITY OF DEALCOHOLIZED WINE. 



Preliminary to its exact determination the extract should be calculated by 

 the formula : 



sp.=l-fa b 



In which " sp." is the specific gravity of the dealcoholized wine, " a " the spe- 

 cific gravity of the wine, and " b " the specific gravity of the alcoholic distillate 

 obtained in the estimation of alcohol. 



Illustration: A sample of Catawba is examined with the following result: 



Sprrific gravity of wine (a) . 1.(>K>12 



Specific gravity of alcoholic distillate (b) . !sr.7 



Difference (a b) .0545 



Specific gravity of dealcoholized wine (1+a b) 1.0545 



Extract (grams per 100 cc) 14.12 



The extract equivalent of " sp." is obtained from Table V, page 218. 



(b) By EVAPORATION. 



(1) IN DRY WINES. 



(Having an extract content of less than 3 grams per 100 cc.) 



Evaporate 50 cc of the sample on the water bath to a sirupy consistency in 

 a flat-bottom platinum dish approximately sr nun in diameter and of about 

 75 cc capacity. Heat the residue for two and one-half hours in a drying oven 

 at the temperature of boiling water and weigh. The sugar-free extract is 



