ETHYL ALCOHOL FROM WOOD WASTE. 21 
commercial practice to fill the fermenters. The length of this period 
depends on the size of the coolers and on the temperature of the 
cooling water and of the neutral juice to be cooled; for the extraction 
of sugar is carried on either at 70° to 80° C. or at 40° to 45° C. in the 
diffusion battery, and the solutions cool only slightly while being 
neutralized and settled. 
At 9.30 a. m., September 26, the first-day Brix reading was taken; 
and at 9.30 a. m., September 29, the beers were distilled for analysis. 
This gave a fermenting period slightly in excess of 96 hours (the time 
allowed by the Bureau of Internal Revenue for a sour-mash fermenta- 
tion), for the filling of the fermenters was actually begun at 3 a. m., 
September 25, instead of at 9.30 a. m., September 24. However, the 
error introduced is practically of no significance, for the attenuation 
on the fourth day is usually only 0.2° Brix at the most. The work 
was greatly simplified by this scheme, and most of it could be done 
in the usual laboratory working hours. 
As will be noted on the sugar and alcohol yield sheets, the fermen- 
tation efficiencies are high; that is, higher than the 90 to 94 per cent 
that would ordinarily be obtained, the chief reasons for this are to 
be found in: (1) The alcohol added along with the starting yeast; 
(2) the unfermented molasses in the starting yeast, which subse- 
quently fermented; 36 (3) errors in sugar determinations; (4) errors 
in sampling. 
The fermentable sugars and fermentation efficiencies are calculated 
as follows, and the effect of the above errors and their magnitude 
will be shown. The wood-sugar solution obtained after neutraliza- 
tion and settling, and hereafter called the neutral juice, is analyzed 
before and after fermentation. The solution after fermentation is 
called the beer. The sugar is always expressed in grams of dextrose 
to the liter, although it was actually a mixture of dextrose, possibly 
other hexoses (as in the case of western larch), and pentoses. The 
following formula gives the percentage of the total sugars that are 
fermentable, expressed as dextrose: 
Dx. in neutral juice, grams Dx. in beer, grams 
per liter per liter 
Sp . gr. of juice "~~ Sp. gr. of beer ioo = Percentage of total 
Dx.m neutral juice sugars fermentable. 
Sp. gr. of juice 
The fermentable sugars are defined as all sugars that have disap- 
peared during fermentation, whether the resulting product is alcohol 
or not. If the product is not alcohol, it will appear in the fermenta- 
tion efficiency figure. If the sugar in the neutral juice before fermen- 
w The 18° Brix molasses worked off to about 12° Brix when it was added to the sprout mash. On the 
fourth day, when a sample of the yeast was distilled for analysis, the Brix readings ranged between 4° 
and 5°. 
