FERMENTED AND DISTILLED LIQUORS. 83 



4. DETERMINATION OF EXTRACT. 

 (a) FROM SPECIFIC GRAVITY OF DEALCOHOLIZED WINE. 



Preliminary to its exact determination, the extract should be calculated by the 

 formula: 



in which sp is the specific gravity of the dealcoholized wine, x the specific gravity 

 of the wine, . y the specific gravity of the alcoholic distillate obtained in the estima- 

 tion of alcohol. 



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

 Specific gravity of wine (#) ...................................... 1. 0402 



Specific gravity of alcoholic distillate (:i -/ ) .......................... 9857 



Difference (x x / ) ................................................ 0545 



Specific gravity dealcoholized wine (1-f-a; x'} ..................... 1 . 0545 



Extract (from Table V) .......................... 14. 48 grams per 100 cc. 



The extract content equivalent to sp is obtained from table. 



(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 consistence in a flat- 

 bottom platinum dish about 85 mm in diameter and capable of holding about 75 cc 

 Heat the residue for two and a halt' hours in a drying oven at the temperature of 

 boiling water and weigh. 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 per 100 cc from the total residue. In the case of plastered wines, 

 the potassium sulphate in excess of 0. 1 gram is also deducted. 



(2) In sweet wines. 



When the extract content is between 3 and 6 grams per 100 cc treat 25 cc of the 

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

 however, the result obtained under (a) is accepted, and it is not attempted to deter- 

 mine it gravimetrically. This is because of the serious error connected with drying 

 levulose at high temperature. The table referred to here was obtained by drying at 

 75 C. in vacuo. 



5. DETERMINATION OF ASM. 



Ignite at low redness, until thoroughly charred, the residue from the determina- 

 tion of extract,* exhaust with water, filter, and wash. Return the filter paper 

 and insoluble material to the dish and burn to a white ash, add the soluble portion 

 and evaporate the whole to dryness, heat to a low redness, cool in a desiccator, and 

 weigh. With dry wines complete combustion can often be obtained without leaching. 



6. DETERMINATION OF TOTAL ACIDS. 



Expel any carbon dioxid that is present by continued shaking. Transfer 25 cc of 

 the sample to a beaker, heat to incipient boiling, and, in the case of white wines, 

 add about 10 drops of a neutral litmus solution and titrate while still hot with 

 decinormal sodium hydroxid solution. With red wines, add dirinorinal sodium 

 hydroxid solution until the red color changes to violet, and continue adding a few 

 drops at a time until a drop of the mixture placed on delicate neutral litmus paper 

 ceases to show an acid reaction. 15 The result is expressed in terms of tartaric acid. 



Employ the residue obtained by evaporating 25 co of the \\inc -when tin- extract lias beencalcu- 



ItUfil from specific gravity. 

 b Sei; Appendix, p. 1 >>. 



