36 BULLETIN 314, U. S. DEPARTMENT OF AGRICULTURE. 
wen 
METHOD. 
The extractor shown in figure 18 was designed upon lines suggested 
by an examination of machines in use by A. E. Schutte and O. N. 
Forrest. It consists of a one-fifth-horsepower 1,100 revolutions per 
minute vertical-shaft electric motor a, with the shaft projecting into 
the cylindrical copper box b, the bottom of which is so inclined as to 
drain to the spout e. A three-sixteenths-inch circular brass plate 94 
inches in diameter is shown in d, and upon this rests the sheet-iron 
bowl e, which is 84 inches in diameter by 23° inches high, and has a 2- 
inch circular hole in the top. Fastened to ihe inner side of the bowl is 
the brass cup f, having a circle of one- 
eighth-inch holes for the admission of 
the solvent, and terminating in the 
hollow axle, which fits snugly through 
a hole at the center of the brass plate. 
The bowl may be drawn firmly against 
a felt-paper ring g, three-fourths inch 
wide, by means of the 24-inch milled 
nut h, for which the hollow axle is 
threaded for a distance of three- 
fourths inch directly below the upper 
surface of the plate. The axle fits snugly over 
the shaft of the motor, to which it is locked 
by a slot and cross pin 2. 
The aggregate is prepared for analysis by 
heating it in an enamel-ware pan on the hot 
plate until it is sufficiently soit to be thor- 
oughly disintegrated by means of a large 
spoon. Care must be taken, however, that 
Fic. 18.—Centrifuge extractor the individual particles are not crushed. If 
a Gees a section of pavement is under examination, 
a plece weighing somewhat over 1 kilogram may be cut off with 
hammer and chisel. The disintegrated aggregate is then allowed 
te cool, after which a sufficient amount is taken to yield on ex- 
traction from 50 to 60 grams of bitumen. It is placed in the 
iron bowl and a ring three-fourths of an inch wide, cut from the 
felt paper, is fitted on the rim, after which the brass plate is placed 
in position and drawn down tightly by means of the milled nut. Hf 
the bitumen is to be recovered and examined, the felt rmg should be 
previously treated in the empty extractor with a couple of charges 
of carbon disulphide in order to remove any small amount of grease 
or resin that may be present, although a proper grade of felt should 
be practically free from such products. The bowl is now placed on 
the motor shaft and the slot and pin are carefully locked. An empty 
bottle is placed under the spout and 150 cubic centimeters of carbon 
