18 BULLETIN 927, I T . S. DEPARTMENT OF AGRICULTURE. 
In this connection, it may be stated that the oils obtained from the 
several lots of seed varied somewhat in color, from a pale golden 
yellow to a deep reddish brown. The lightest colored oil was ob- 
tained from heated seed dried in a rotary drier. This lot, however, 
gave the lowest yield of oil. The uncleaned seed yielded the darkest 
colored oil. Not enough difference was noted in either the yield or 
character of the oils to warrant the assumption that the heating or 
fermenting of seed, such as would probably take place in transit from 
the pulping station to the central reduction plant, would have an 
especially deleterious effect on the oil. 
Solvent extraction of oil-bearing seed is at present receiving the 
attention of oil technologists, principally because of the higher yield 
of oil obtainable. It consists essentially of percolating the material 
with a suitable solvent which dissolves the oil and is subsequently 
recovered from the oil solution and from the residue by distillation. 
Benzol is perhaps the most satisfactory solvent used for this purpose 
at the present time. However, other solvents, such as gasoline, petro- 
leum ether, and carbon tetrachlorid, are of value. 
In the experiment made in the laboratory the seed was ground and 
extracted with benzol by maceration. The solution of the oil in 
benzol was placed on a steam bath and freed from the solvent hj 
vacuum distillation. The yield of oil by this process was 20.7 per 
cent. 
A modified method of solvent extraction is embodied in the so- 
called Cobwell process (fig. 11), which is being applied in garbage 
utilization and for other similar purposes. This process is applicable 
to oil-bearing materials with a high content of water. The process 
operates on the principle that when a wet mass is mixed with a 
volatile solvent and distilled the vapor tension of both water and 
solvent is lowered, whereby the mixture of the two vapors passes over 
into the condensing system. By renewing the solvent from time to 
time as the liquid mixture boils off it is apparent that the later distil- 
lates will become richer in solvent and weaker in water until practi- 
cally all the water has been eliminated. Distillation is then stopped 
and the mass percolated with the solvent, whereby the oil is extracted 
and drained off with the solvent. This solution is pumped into a still 
and heated, which causes the solvent to vaporize and condense in an 
appropriate equipment, while the oil remains behind in the still. 
It is apparent that this process obviates the necessity for seed 
separation, moisture reduction, and drying and at the same time 
yields the oil in one treatment of the raw waste. 
The disadvantage of the process and of the one previously de- 
scribed is that both yield solvent oils, which bring a lower market 
price than pressed oils. 
