The Dawson news. (Dawson, Ga.) 1889-current, 1914-08-21

been refined are the following: Ope-
cific gravity, 1882; color of powder
or streak, black; luster, bright;
structure, uniform; fracture, semi
conchoidal; hardness, original sub
stance. at IT degrees F., soft; odor,
individually asphaltic; melting point,
ISL degrees F.; penetration at n
degrees F. in 3 seconds of 100 grams
on a No. 2 needle; loss from 20
grams at 1926 degrees F. for hours
in ~ inch dish, 20 per cent; and
20 grams at 400 degrees F. for Z
hours in 2A inch dish, II per cent;
character of residues in both cases,
smooth and the penetration is LIZ
nm. and 4 nm. respectively for the
two Temperatures. The ultimate
composition of the pure bitumen OF
the Bermudez is the same as that OF
the Trinidad bitumen, as can be seen
from the following comparison;
BermudeZ Trinidad
Carnob .. 1928 per ct. 1868 per ct.
Hydrogen 1918 per ct. 1863 per ct.
Sulphur 5.8 per ct. Gle per ct.
Nitrogen rs per ct. 81 per ct.
1t is noticeable that both of these
contain a large per cent of sulphur.
That of BermudeZ varying, however,
according to the degree to which the
material has become hardened at dill
ferent points in the deposit, the soft
est material containing the largest
percentage.
1t is to the sulphur that is present
that the valuable properties of the
Trinidad and Bermudez bitumens are
attributed to a large extent. Mr..
Richardson says that asphalt is in
process of formation today. 1t plain
ly does not originate as such, but is
a secondary product, resulting from
the transformation of suitable light
err forms of bitumen matthias or even
thin oils into harder bitumen by con-
densation and pOlymerization. A re-
action in which sulphur and probably
sulphates seem to take an important
part" This conclusion was based on
the fact that an ultimate analysis
made by him of the pure bitumen
from twelve to fourteen solid as
phalts taken from various parts of
the world showed the presence OF
from Ats per cent to 9:76 per cent
of sulphur; while in the softer forms
of bitumen which harden rapidly up
on exposure to air or on heating only
2 per cent is found.
DR.. D. Holde said that "a bitumen
would be called native asphalt when
it contains considerable amounts
Casually over per cent? of sulphur
not removable by steam, when the
amount of the latter in the chloro-
form extract which is insoluble in
benzol is at least rs per cent and
the asphalt, separated according to
the method of MarcassOn and Erck-
mann, contains IA per cent to 81
per cent of oil with at the most 70
per cent paraffin." He says further,
" a bitumen would be called petro-
leum residual pitch if it contains at
most II per cent of sulphur, ever in
the chloroform extract prepared as
previously described and from 70 TO
SO per cent of oil in which the par
ATTN amounts to 3.3 per cent to 1876
per cent. 1t appears, therefore, that
native solid asphalt is character1Z-
per cent of sulphur. A very import
ant physical characteristic that the
sulphur gives to the material is to
make it less susceptible than the re-
sidual oils and pitches to change IN
consistency with change of tempera-
ture in the solid asphalts. Since the
Trinidad and the Bermudez asphalts
contain a large percentage of sui
phur it is natural that they would be
more desirable for use in highway
construction than the residual pitch
es prepared from petroleum oil.
Cement made from Trinidad and
Bermudez asphalt is very nearly the
same in all respects. The Trinidad
has a slight advantage. They are
both characterized by definite spe-
cific gravity; by certain ductility, as
determined by a conventional test;
by containing but little volatile mat
ter so that when the cement is heat
ed for some time at the temperature
at which it is used the loss does not
exceed a small percentage and the
consistency is not reduced to an
alarming degree; by the fact that it
has a certain VisOSity with which oth-
er asphalt cementS can be c0mpar-
ed; and by its having large amount
of sulphur which has an important
bearing on its stability. The cements
in addition possess adhesive, binding
and eementing properties, and are
short, cheesy and oily. They do not
harden excessively when exposed to
low temperatures or become too Ii
quid under the summer sun. They
do not contain large amounts of light
oils, volatile during the period in
which the material is in melted
condition. They have great viscOsity
at ordinary temperatures but be
come sufficiently mobile at high tenn
peratures to mix satisfactorily with
the mineral aggregate.
AS before stated, the Trinidad as
phalt is preferable to Bermudez. Its
successful use may be attributed to
the entire uniformity of the material
as it is found in the so-called lake
deposit in the island of Trinidad. 1t
has, besides these stated, the
desirable properties of stability
under which may be included
oh a