158 AMOUNT OF ALCOHOL IN WINE. 



It is useless to take three decimal points, for the 

 observations cannot be made accurately. 



The principle upon which this method rests is 

 simply this, alcohol decreases, arid non-volatile sub- 

 stances increase the specific gravity of wine. If the 

 alcohol be allowed to evaporate, its quantity must be 

 determined, as far as may be, by ascertaining the dif- 

 ference between the specific gravity of the wine and 

 that of the residue to which water has been added. 



It is self-evident that even this method cannot be 

 absolutely accurate, since the solid constituents are 

 differently circumstanced in wine, according as alcohol 

 is present or non-present. The only question of im- 

 portance here is, whether the method be serviceable ; 

 that is, whether the strength of the wine can be de- 

 termined by it with sufficient accuracy. Experience 

 has taught me that it is applicable, and I have no 

 hesitation in preferring it to every other method, when 

 a large number of wines are to be examined. It is 

 only necessary to measure off a certain quantity of 

 wine with a pipette, the contents of which are known, 

 and to ascertain its temperature and specific gravity 

 (which can be done, if preferred, by an areometer), 

 then place this wine in an open glass in a water-bath, 

 till about half has evaporated ; water must then be 

 added to it till its original volume is restored ; it must 

 be reduced again to its original temperature, and its 

 specific gravity ascertained, thence the alcoholic con- 

 tents of the wine can be learned. And indeed the 



