EXAMINATION OF WINE. 55 



bath, and the residue is transferred to a small glass-stoppered graduated 

 cylinder with 20 cc of absolute alcohol, and three portions of 20 cc each 

 of absolute ether added, with thorough shaking at each interval. Let 

 stand until clear, then pour off through a filter, and wash the cylinder 

 three times or more with a mixture of one part absolute alcohol to 

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

 through the filter. The nitrate is evaporated to a sirupy consistency, 

 dried for one hour at the temperature of boiling water, and weighed. 

 The weight of the residue is multiplied by two for the grams of 

 glycerol per 100 cc. 



ESTIMATION OF EXTRACT. 



In dry wines. Fifty cc of the sample are evaporated on the water 

 bath to a sirupy consistence in a flat-bottom platinum dish about 85 

 mm in diameter and capable of holding about 75 cc. The residue is 

 heated for two and a half hours in a drying oven at the temperature 

 of boiling water and weighed. This weight multiplied by 2 gives 

 grams of total residue in 100 cc. The sugar-free extract is found by 

 deducting the weight of sugar in excess of 0.1 gram from the total 

 residue. In the case of plastered wines, the potassium sulphate in 

 excess of 0.1 gram is also deducted. 



In sweet wines. Twenty -five cc of the sample are treated as described 

 under dry wines. When the extract exceeds 6 grams per 100 cc, 

 however, the extract is to be obtained from the specific gravity of the 

 dealcoholized' wine, which may be calculated from Table II according 

 to the formula: Specific gravity of dealcoholized wine = 1 -f x a/, 

 wherein x the specific gravity of the wine, and x' the specific 

 gravity of the alcoholic distillate obtained in the estimation of alcohol. 

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



Specific gravity of wine (x) 1.0402 



Specific gravity of alcoholic distillate (x') 9857 



Difference (a; -a/) - 0545 " 



Specific gravity dealcoholized wine (1 -\- x x'} 1.0545 



Extract (from Table II) 14.48 grams per 100 cc. 



ESTIMATION OF ASH. 



The residue from the determination of extract is ignited at low 

 redness, until thoroughly charred, extracted with water, filtered, and 

 washed. The filter paper and insoluble material are returned to the 

 dish and burned to a white ash, when the soluble portion is added 

 and the whole evaporated to dryness after the addition of a few cc 

 of ammonium carbonate, heated to a low redness, cooled in a desiccator, 

 and weighed. 



ESTIMATION OF TOTAL ACIDS. 



Expel any carbon dioxid that is present by continued shaking. 

 Transfer 25 cc of the sample to a beaker and, in the case of white wines, 



