90 TRANSACTIONS OF THE 
gave very concordant results. The specific gravity ‘is in 
all cases very close to one. 
The softening and flow temperatures were determined 
by putting a small angular piece of the bitumen on a micro- 
scopic slide cover glass placed upon a mercury bath and then 
heating the mercury. 
A funnel was adjusted over the sample and glass. A 
thermometer passed through the funnel neck registered the 
temperature of the bath and of the sample. When the 
first signs of the rounding of the edges and corners was 
noted that temperature was taken as the softening temper- 
ature. The heating was continued until the sample flat- 
tened out as a liquid on the glass. This gave the tempera- 
ture of flow. Where the temperature was above the boiling 
point of mercury no determination was made. 
The fracture was determined by looking at a freshly 
broken surface. It was found to be conchoidal in all cases; 
that is, the surface appears to be made up of a series of 
concentric spheres. 
The loss upon heating to 212 degrees F. for one hour 
gives the moisture and the very low boiling distillates. These 
values are quite low, as are the values for 325 degrees F. 
for seven hours, and account in considerable measure for 
the zero penetration found in all cases except the ozokerite. 
The oven used to obtain a constant temperature was an 
ordinary air oven, asbestos covered, with a fan at the bottom 
to keep the air in circulation, thus preventing one part of 
the furnace becoming hotter than another. Considerable 
difficulty was found in the seven hour run at 400 degrees 
F. to keep the temperature constant, as the gas pressure in 
the burner varied greatly. 
The penetration is the distance a number two sewing 
machine needle will penetrate the sample when released for 
five seconds with a 50 gram weight upon it. For the use 
of the standard machine for making these tests we are in- 
debted to the testing laboratory, City Engineer’s Office, 
Salt Lake City. 
The bitumens in the asphalts are divided into two 
general classes.*t. Those soluble in 62 degrees naphtha are 
“Modern Asphalt Pavement’, by Richardson, p. 118. 
