34 BULLETIN 314, U. S. DEPARTMENT OF AGRICULTURE. 
is poured into the filter tube, the te™perature of which has been 
reduced to —20° C. From one to two grams of the well-mixed dis- 
tillate obtained in the manner previously described is then accurately 
weighed in a 100 cubic centimeter Erlenmeyer flask, mixed with 10 
cubic centimeters of Squibbs’ ether, and poured into the filter tube. 
Ten cubic centimeters of absolute alcohol is next placed in the flask 
to wash out the ether solution, poured into the filter tube, and the 
cover carrying the 
thermometer placed 
on the tube. The 
mixture is maintained 
at a temperature of 
— 20° C. for 15 min- 
utes, then the cork 
stopper is removed 
from the outlet of 
the filter tube and 
the filtermg flask is 
replaced. The corks 
supporting the ther- 
mometer are now 
icosened and a strong 
suction is applied to 
the filter fiask until 
all of the solvent is 
drawn. off. The con- 
tents of the filter tube 
are next washed with 
10 cubic centimeters 
of a 1 toi mixture of 
Squibbs’ ether and ab- 
solute alcohol, which 
is chilled to —20° C. 
in the filter tube be- 
fore suction is applied. 
When the washings 
have been removed the vacuum is turned off and the filter tube removed 
from the apparatus. The filter tube is then placed in a clean filter 
flask which also contains a 6-inch test tube in which the dissolved 
paraffin scale is later collected. About 10 cubic centimeters of warm 
petroleum ether is poured into the filter tube and allowed to remain 
until the paraffin scale has been dissolved. Vacuum is then applied 
and the dissolved scale drawn into the test tube. This treatment is 
followed by two washings, one of 10 cubic centimeters and the other 
of 5 cubic centimeters of warm petroleum ether, which removes the 
last traces of paraffin scale. The entire contents of the test tube are 
Fic. 17.—¥F reezing apparatus for determining paraffin scale. 
