66 BULLETIN 983, U. S. DEPARTMENT OF AGRICULTURE. 
size of the material that is to be cooked, as, for instance, sawdust will 
extract more readily than larger material. As the sugars are readily 
soluble, only a short extraction period is necessary — that is, from 5 to 
10 minutes on each cell — making a total extraction period of 50 to 75 
minutes. This period, however, will be governed in part by the 
length of time that it takes the water to drain through each cell, and 
this in turn depends on the size of the cell. 
The cells should not be too large, else the extracting water will not 
pass through the material easily, and there will be a tendency to 
channel. The amount of water used should be such as to make the 
resulting acid extract 11° to 12° Brix, the proper concentration for 
fermentation. The Brix will rise another degree on neutralization. 
As in laboratory work, so in regular practice, a large number of 
extractions or washings with small amounts of liquid will give a 
better extraction or a more thorough washing with a more concen- 
trated extract than will fewer extractions with larger amounts of 
water for each extraction. 
NEUTRALIZATION AND SETTLING. 
After extraction the acid extract is nearly neutralized with lime 
or a high-grade limestone. For this purpose a magnesia stone is 
undesirable. For a number of reasons it has been found preferable 
to cool the acid juice to 100° F. or less before it is neutralized. During 
neutralization the temperature will rise a few degrees. The extract 
is then allowed to stand and settle out the sludge of calcium sulphate. 
As this usually requires from 15 to 18 hours, adequate tank capacity 
is required. 
COOLERS. 
The clear juice is then drawn off and passed through coolers to 
reduce its temperature to from 80° to 90° F., after which it goes into 
the fermenting tanks. The coolers should be of copper, and their 
size will depend upon the temperature of the water supply available. 
As the calcium sulphate in the neutral juice will partially crystallize 
out during the cooling, the coolers should be so designed as to be 
easily taken apart and cleaned. 
FERMENTATION, DISTILLATION, ETC. 
A 96-hour fermentation period is permitted; hence a 4-day fer- 
menter capacity is required. The size of the individual fermenter 
will be determined largely by the outdoor mean temperature and 
other local conditions. The other apparatus is the standard distillery 
equipment in use in grain and molasses distilleries. 
