FERMENTATION 583 



Alcoholometry . Unfortunately in Great Britain and her colonies alcohol 

 is measured in " proof " ; a more annoying system could barely have been 

 devised. By proof is meant one which at 62 F. weighs |f of an equal bulk 

 of water ; 40 over proof (O.P.) means that 100 volumes of the spirit contain 

 as much alcohol as 140 volumes of proof ; 40 under (U.P.) means that 140 

 volumes of the spirit contain as much alcohol as 100 volumes of proof. 

 Absolute alcohol is 75-25 O.P., so that to convert volumes of proof spirit to 

 alcohol it is necessary to divide by 1-7525 and vice versa. Proof spirit 

 contains 49 3 per cent, by weight or 57 06 per cent, by volume of alcohol. 

 In France, and also in Germany, the Gay-Lussac scale is used ; this is the 

 most rational one and gives directly the percentage of alcohol by volume. 

 The Cartier scale is an empirical one, 43 beihg absolute alcohol and 22 being 

 proof spirit. The Beck scale is also an empirical one, 43-9 being absolute 

 alcohol and 14-8 being proof spirit. In the U.S.A. the Gendar scale is used ; 

 200 is absolute alcohol, 100 is U.S. proof (i.e., 50 per cent, by volume) and 

 o is water. 



The bubbles used in distilleries as a guide in the test case are based on 

 the Cartier scale ; they are numbered from 16 to 30 ; bubble 25 corresponds 

 to 25 Cartier, but bubble 26 corresponds to 24 Cartier, &c. 



COMPARISON OF THE DIFFERENT ALCOHOL SCALES. 



Beck. Gendar. Bubble 



44 .. 200 



38 .. 190 



34 .. 180 



30 .. 170 .. 17 



27 .. 160 .. 19 



24 .. 150 .. 21 



21 .. 140 ., 23 



18 .. 130 .. 25 

 16 .. 120 . . 27 

 14 ,. no .. 29 



12 .. 100 .. 30 



10 ..90 .. 



9 . , 80 . . 



7 .. 70 .. 



6 .. 60 .. 



5 5 

 4 . . 40 . . 



3 30 



2 . . 2O . . 



I .. 10 .. 



O .. O .. 



Obscuration. The obscuration of a spirit is the difference between 

 the actual proof strength and the apparent proof strength as determined by 

 an immersion alcoholometer. Thus spirit showing 40-0 over proof by the 

 alcoholometer, and of actual strength 43-1 over proof is said to have an 

 obscuration of 3-1. In some cases, however, the obscuration is expressed 

 on the proof spirit, so that for the example quoted the obscuration is 



= 2*17 per cent, on proof spirit. 



