52 
BULLETIN 691, U. S. DEPARTMENT OF AGRICULTURE. 
d-~- 
6 — 
Dieters wide at the top, tapering to 3.6 centimeters at the bottom, and is 2.5 
centimeters deep. 
For preparing the felt the necessary appartatus Is arranged as shown in 
figure 6, in which a is the filtering flask, & a rubber stopper, c the 
filter tube, and d a section of rubber tubing which tightly clasps the Gooch 
crucible c. The asbestos is cut with scissors into pieces not exceeding 1 
centimeter in length, after which it is shaken up with just sufficient water to 
pour easily. The crucible is filled with the suspended asbestos, which is 
allowed to settle for a few moments. A light suction is then applied to draw 
off all the water and leave a firm mat of asbestos in the crucible. More of the 
suspended material is added, and the operation is repeated until the felt is so 
dense that it scarcely transmits light when held so that the bottom of the 
crucible is between the eye and the source of light. The felt should then be 
washed several times with water and drawn firmly against the bottom of the 
crucible by an increased suction. The crucible is removed to a drying oven 
for a few minutes, after which it is ignited at 
red heat over a Bunsen burner, cooled in a 
desiccator, and weighed. 
From 1 to 2 grams of the bituminous material 
is now placed in the Erlenmeyer flask, which has 
been previously weighed, and the accurate 
weight of the sample is obtained. One hundred 
cubic centimeters of chemically pure carbon 
disulphide is poured into the flask in small 
portions, with continual agitation, until all 
lumps disappear and nothing adheres to the 
bottom. The flask is then corked and set aside 
for 15 minutes. 
After being weighed, the Gooch crucible con- 
. taining the felt i3 set up over the dry pressure 
flask, as shown in the figure, and the solution 
of bitumen in carbon disulphide is decanted 
through the felt without suction by gradually 
tilting the flask, with care not to stir up any 
precipitate that may have settled out. At the 
first sign of any sediment coming out, the decantation is stopped and the 
filter allowed to drain. A small amount of carbon disulphide is then washed 
down the sides of the flask, after which the precipitate is brought upon the 
felt and the flask scrubbed, if necessary, with a feather or " policeman," to 
remove all adhering material. The contents of the crucible are washed with 
carbon disulphide, until the washings run colorless. Suction is then applied 
until there is practically no odor of carbon disulphide in the crucible, after 
which the outside of the crucible is cleaned with a cloth moistened with a 
small amount of the solvent. The crucible and contents are dried in a hot-air 
oven at 100° C. for about 20 minutes, cooled in a desiccator, and weighed. If 
any appreciable amount of insoluble matter adheres to the flask, it should also 
be dried and weighed, and any increase over the original weight of the flask 
should be added to the weight of insoluble matter in the crucible. The total 
weight of insoluble material may include both organic and mineral matter. 
The former, if present, is burned off by ignition at a red heat until no incan- 
descent particles remain, thus leaving the mineral matter or ash. which can 
be weighed on cooling. The difference between the total weight of material 
insoluble in carbon disulphide and the weight of substance taken equals the 
total bitumen, and the percentage weights are calculated and reported as total 
Fig 
-Apparatus for determin- 
ing soluble bitumen. 
