66 BUIXETIN 1216, U. S. DEPARTMENT OF AGRICULTURE. 
.1 small gas jet. Tlie dish of bitumen should then be set in a 
hot -air oven maintained at lo."° C. for about an hour, after 
which it should be allowed to cool, its general character 
is noted and any testa for bitumens that are necessary are then 
made upon it. 
The difference between the final aggregate and the orignal 
amount taken gives the amount of bitumen extracted, which 
is subject t<» correction, dependent on the amount of ash deter- 
mined from the washings. 
Ash, correction shall be made in the following manner: The 
total solution of bitumen, well stirred, is rapidly measured and 
an aliquot portion taken, usually LOO cubic centimeters, and 
ponced into ;i previously weighed suitable flat-bottom dish, pref- 
erably quart z. The solvent is evaporated over a very low flame 
and the residual coke is then ignited with a burner capable of 
furnishing high temperature, such as a Meker. (Caution: When 
an inflammable solvent is used evaporation should be conducted 
on a steam hath and care should he taken that no flames are in 
the immediate vicinity.) The dish and contents are then cooled 
in a desiccator and the percentage of ash calculated. 
R Hot Extraction Method. 
Hot extraction The New York Testing Laboratory extractor <<msists of a large 
method. brass cylinder, through the bottom of which projects a 10-ean- 
dlepower incandescent carbon-filament bulb to supply heat to 
the extraction apparatus proper, which is held in the upper por- 
tion of the cylinder. This apparatus is composed of a cylindrical 
brass vesso] for holding the solvent, a cylindrical wire basket 
made of 80-mesh wire cloth, suspended in the cylinder, and an 
inverted conical condenser which serves as a top. 
The aggregate is prepared for analysis by heating it in a tin 
dish on the hot plate until it is sufficiently soft to be disintegrated 
by means of a large spoon. The disintegrated aggregate is then 
allowed to cool. Not less than 500 grams of aggregates contain- 
ing particles larger than three-quarters inch in diameter or 200 
grams of aggregates with all particles smaller than three-quarters 
inch are then closely packed in the wire basket or suitably sized 
extraction thimbles and covered with a disk or wad of absorbent 
cotton or felt. From 175 to L'OO cubic centimeters of carbon di- 
SUlphide (carbon tetrachloride, benzol, or chloroform may be 
used) are next placed in the inside vessel, in which the wire 
basket should be suspended. The top is then placed in position 
and cooling water circulated through it. Heat is applied by 
means of the electric-light bulb. The solvent is boiled in the 
lower pari of the extractor and condenses on the undersurface of 
I he top, from which it drips upon the wad of absorbent cotton and 
then percolates through the sample. A complete extraction may 
he made in three hours. At the end of this time the apparatus is 
allowed to cool and the basket containing the extracted aggregate 
carefully removed. After thoroughly drying, the aggregate is 
placed upon a pan of the rough balance ami weighed. The differ- 
ence between this weight and the original weight taken shows the 
amount of bitumen extracted, which is calculated upon a per- 
centage basis of the original. This figure should be corrected for 
fine mineral matter which passes through the meshes of the wire 
basket, as follows: The solution of extracted bitumen is thor- 
oughly agitated and measured in a glass graduate. Five or ten 
cubic centimeters are then poured into a weighed platinum cruci- 
ble or dish, burned, and Ignited to ash. The amount of mineral 
matter in the entire solution may then be calculated from the 
amount of ash produced from that portion ignited. The total 
percentage of snch ash is then deducted from the percentage of 
bitumen already calculated in order to obtain the true percentage 
of bitumen; The amount of this correction will ordinarily vary 
from 0.1 per cent in uniformly coarse aggregates to 1 or 2 per cent 
in the analysis of aggregates containing a considerable amount of 
very fine mineral matter. 
