FERMENTED AND DISTILLED LIQUORS. 



93 



in which sp is the specific gravity of the dealcoholized beer, g the specific gravity of 

 the beer, and a the specific gravity of the distillate obtained in the determination 

 of alcohol. In place of this formula, the residue from the distillation of alcohol is 

 sometimes diluted to the original volume, and its specific gravity taken. This is often 

 impracticable owing to the necessity of employing tannin to prevent foaming in the 

 distilling flask, and owing to the coagulation of proteids during the distillation. 



The extract of beer can not be accurately determined by evaporation and drying 

 at the boiling point of water because of the dehydration of the maltose. 



5. DETERMINATION OF ORIGINAL GRAVITY OF WORT. 



The various methods employed to obtain this figure depend on the fact that the 

 sugars yield about half their weight of alcohol when fermented. 

 Employ the formula: 



G=sp+si 



in which G is the specific gravity of the original wort, sp the specific gravity of 

 the dealcoholized beer (see 4), and si the amount of saccharine matter destroyed by 

 fermentation obtained from the following table: 



Saccharine matter lost by fermentation. * 



In this table, 1 a is found by deducting from 1.0 the specific gravity of the 

 alcohol distillate obtained in the determination of alcohol. In case of beer of high 

 acidity, it must be increased by the value of 6 in the formula 



&= 0.9* -0.14, 



in which I is the percentage of acid calculated to lactic acid. The figure 0.14 is 

 taken as the alcoholic equivalent of the average acid content of beer (ordinarily 

 about 0.15 percent lactic acid), and is deducted for that reason. The table here 

 given is that of Graham, Hofmann, and Redwood, b except that it is expressed here as 



Alien, Com. Org. Anal., Vol. I. 



b Report on Original Gravities, 1852; Allen, Commercial Organic Analysis, 3d edition, Vol. I, p. 136. 



