pletely converted into maltose. The form 
of the mashing apparatus and the tem- 
peratures at which the several operations 
are conducted are modified as may be 
necessary to fit the peculiarities of the 
raw materials. 
In this country maize is the chief 
starchy material used in the manufac- 
ture of alcohol. It is mashed in a sort 
of kettle known aS a vacuum cooker. 
The vacuum cooker is a horizontally 
placed cylindrical vessel made of steel 
boiler plate, and has a capacity of about 
40 gallons for every bushel of grain to 
be mashed in one charge. Just below 
the center of each end it is provided 
with stuffing boxes, through which a shaft 
passes. The latter carries several rakes 
or stirring arms inside the shell; outside 
it is provided with a strong toothed wheel, 
arranged for chain drive. Thermometers 
and try cocks are mounted in each end 
of the shell, and if the cooker is large a 
third thermometer is set in the middle 
of the side. In a row along the bottom 
are several small steam-inlet valves so 
constructed that while steam can pass 
freely into the cooker the contents of the 
latter can not run back into the steam 
pipe when pressure is removed outside. 
At the middle of the top of the cooker is 
a dome fitted with a pipe connection 
which leads to a “cross.” From one side 
of the latter connection is made to the 
steam supply, which must be carried at 
about 50 pounds pressure; from the other 
side connection is made with the vacuum 
pump, and from the top a pipe leads to 
a blow-off valve. On top of the cooker, 
at one end, there is a manhole through 
which water and meal may be introduced, 
and in the bottom, at one end, there is a 
discharge valve which opens into a pipe 
leading to the drop tub. The operation 
of this cooker is as follows: 
Water in the proportion of 20 to 25 gal- 
lons for every bushel of corn is first run 
in and is warmed up to about 120 degrees 
Fahrenheit. The rakes are then started 
and the grain, which should be ground to 
a coarse meal, is added slowly enough to 
keep it from forming lumps. When the 
meal is all in, the manhole is closed and 
26 ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
steam is turned on through the small 
valves in the bottom, the blow-off valve 
being left open. When the temperature 
of the mash has risen to 212 degrees the 
blow-off valve is closed and pressure is 
allowed to rise within the cooker at such 
a rate that the thermometers and a pres- 
sure gauge in the dome indicate a fairly 
constant equalization of temperature in 
the contents. The pressure is allowed to 
rise to about 50 to 55 pounds, correspond- 
ing to a temperature of about 300 degrees 
Fahrenheit, but is maintained at this 
point for a few minutes only, after which 
the steam is shut off and the blow-off valve 
is opened until the pressure is completely 
relieved. The blow-off valve is then closed 
again, and the valve between the cooker 
and vacuum pump is opened. Application 
of the vacuum causes renewed boiling and 
a rapid fall of temperature in the con- 
tents of the cooker, and when the ther- 
mometers read from 140 degrees to 145 de- 
grees Fahrenheit the vacuum is released 
and the malt is added. 
The amount of malt employed is usu- 
ally about one-tenth of the weight of corn 
in the mash. It is ground quite fine and 
is mixed in the small grain tub with 
enough lukewarm water to make it flow 
freely through the pipe which leads to the 
cooker. The length of time allowed for 
saccharification in the cooker will vary 
from fifteen minutes to an hour, accord- 
ing to the temperature—which should be 
held between 140 degrees and 145 degrees 
Fahrenheit—and the amount and diastatic 
strength of the malt. It is advisable not 
to hasten this part of the mashing process 
unduly, and the completeness of the 
starch conversion should always be proved 
Fig. 1. 
A, boiler or kettle of still; B, opening for filling 
Small Laboratory Still. 
or charging; 0, thermometer, sometimes 
omitted; D, connection to condenser; DG, 
inner condenser tube, passing through HF, 
water jacket, with water inlet at #, and 
outlet at F; G, outflow for distillate. 
