EXAMINATION OF BITUMINOUS ROAD MATERIALS, ol 
1899, volume 21, page 1116. One gram of the material is placed in 
a platinum crucible weighing from 20 to 30 grams and having a 
tightly fitting cover. It is then heated for seven minutes over the 
full flame of a Bunsen burner, as shown in figure 15. The crucible 
should be supported on a platinum triangle with the bottom from 
6 to 8 centimeters above the top of the burner. The flame shouid 
be fully 20 centimeters high when burning freely, and the determi- 
nation should be made in a place free from draits. The upper sur- 
face of the cover should burn clear, but the under surface should 
remain covered with carbon, excepting 
in the case of some of the more fluid : 
bitumens, when the under surface of the | | 
cover may be quite clean. 
The crucible is removed to a desiccator ear: | 
\ 
and when cool is weighed, after which fy 
the cover is removed, and the crucible | fi \ | 
is placed in an inclined position over the ri \ 
Bunsen burner and ignited until nothing TH 
but ash remains. Any carbon deposited Pah tase 
on the cover is also burned off. The 
weight of ash remaining is deducted from 
the weight of the residue after the first ! / 
ignition of the sample. This gives the : 
| 
20 Crm 
i 
———— 
6 fo8cem 
miss —a 
weight of the so-called fixed or residual 
carbon, which is calculated on a basis of i 
the total weight of the sample, exclusive 
of mineral matter. if the presence of a 
carbonate mineral is suspected, the per- c= = : 
centage of mineral matter may be most Fie. 15—Apparatus for determining 
accurately obtained by treating the ash ee ae 
with a few drops of ammonium carbonate solution, drying at 100° 
C., then heating for a few minutes at a dull red heat, cooling and 
weighing. 
An excellent form of crucible for this test is shown in figure 15. 
Jt has a cover with a flange 4 millimeters wide, fitting tightly over 
the outside of the crucible, and weighs complete about 25 grams. 
Owing to sudden expansion in burning some of the more fluid bitu- 
mens, it is well to hold the cover down with the end of the tongs 
until the most volatile products have burned off. 
Some products, particularly those derived from Mexican petro- 
leum, show a tendency to suddenly expand and foam over the sides 
of the crucible in making this determination, and no method of 
obviating this trouble without vitiating the result has thus far been 
forthcoming. Recent experiments in the laboratory of the Office of 
