THE PRODUCTION OF CORN OIL. 9 
These figures relating to the quantity of germs and oil obtained 
from a bushel of corn are considered fairly representative and will 
be used in a later section on the economics involved in expelling 
the oil. ) 
Before the oil can be expelled the germ material must be cracked 
or ground. The germs from the dry process are ground less fine, 
as a rule, than those obtained from the wet process. The former, 
which contains some bran and husks, can be ground in an attrition 
mill if necessary, but in most cases all germ material is cracked by 
being passed between rollers. 
Without doubt the expeller is recognized as the ideal type of 
machine for removing the oil from corn germs and is almost univer- 
Fic. 8.—Type of drier used in drying corn germs and feed. 
sally used. (Fig. 9.) The dried germ is tempered with steam, which 
heats it and also adds moisture. It might seem that if there were 
less drying in the first place the subsequent addition of moisture 
would be unnecessary, but it is evidently a case of first removing 
the interior moisture and then adding surface moisture when tem- 
pering. On this point operators are agreed. 
The pressure at which these machines are operated determines 
largely the quantity of oil left in the cake. Several factors are in- 
volved which limit the pressure that can safely be maintained. In 
the first place, increased pressure always involves a decrease of ca- 
pacity. Furthermore, the opinion obtains generally that if the pres- 
sure is too great the oil and cake will both darken, which is very 
undesirable. The wear and tear on the machine is also excessive 
under such circumstances, and consequently, as a rule, no effort is 
made to reduce the oil in the cake below 5 per cent when operating 
2467 °—20——2 
