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CASTOR-OIL. INDUSTRY. 2 25 
solution of oilinthesolvent. Such extractors are made in various sizes 
and may be from 5 to 8 feet in diameter and from 12 to 18 feet 
long. The solvent and steam are introduced through openings in the 
top; the saturated solvent and steam are drawn off at the bottom. 
Another type introduces steam and solvent through a journal bear- 
ing in the axis at one side and discharges steam and saturated solvent 
through a similar opening in the axis on the other side, first passing 
through a perforated false head which divides the discharge end of 
the tank, nto a small compartment into which the filtered solvent 
collects. The smallest of such units will hold about 3 tons of oleagi- 
nous material to the charge, while the large ones may hold as much 
as 6 tons. The total period of treatment from the time of the com- 
mencement of loading back to the corresponding stage of the suc- 
ceeding batch may be about 12 hours, enabling the units to be used 
twice in 24 hours. The channeling of the batch is obviated by rotat- 
ing the tank at intervals, thus breaking up pockets and other deter- 
rents of good extraction. 3 , 
With the exception of the form of the extractor, the rest of the 
solvent plant is quite standard and simple. The solvent-recovery 
still may be provided with a steam jacket on the bottom with auxiliary 
heating coils, or with a calandria somewhat similar to that used with 
sugar pans (simulating an upright fire-tube boiler) where steam cir- 
culates on the outside of the tubes while the evaporating charge 
boils up inside the tubes and down wider openings provided for the 
purpose. An open steam coil is also provided in the bottom of the 
still for blowing off final traces of solvent at the end of the operation. 
The oil-finishing still is very similar in construction to the solvent- 
recovery still, and where such installation is made its purpose is 
to complete the operation of removing the solvent left unfinished in 
the preceding solvent-recovery unit. Where the latter is used for 
the preliminary separation of oil and solvent, these stills, particu- 
larly the oil-finishing still, should be equipped for operating under 
vacuum, 
The solvent and water separator is usually a tank with a separate 
compartment and overflow for drawing off the water which has set- 
tled from the distilled mixture of solvent and water. Such separation 
must be effected in a quiescent condition, because even a slight agi- 
tation of the layers precludes quantitative recovery. It may be 
necessary to install a preliminary water-solvent separator to take 
up the pumping pulsations in order to obviate the churning effect 
when the vapors and condensed liquor are discharged direct from the 
vacuum pump during any part of the boiling-off operation. 
The other equipment of such a plant consists of storage tanks for 
saturated solvent and oil, for solvent alone, and for oil; also a solvent 
heater, boilers, and conveyors. All storage tanks should be pro- 
