48 BULLETIN 949, U. S. DEPARTMENT OF AGRICULTURE. 
all adhering bitumen. The reported penetration shall be the average of at least 
three tests whose values shall not differ more than four points between maximum and 
minimum. 
[b) When desirable to vary the temperature, time, and weight, and in order to 
provide for a uniform method of reporting results when variations are made, the 
samples shall be melted and cooled in air as above directed. They shall then be 
immersed in water or brine, as the case may require, for one hour at the temperature 
desired. The following combinations are suggested: 
At 0° C. (32° F.), 200-gram weight, 60 seconds. 
At 46.1° C. (115° F.), 50-gram weight, 5 seconds. 
30. DETERMINATION OF DUCTILITY OF BITUMINOUS MATERIALS. 
(Method described in Trans. A. S. C. E., vol. 82, 1918, p. 1460.) 
A briquette of the material to be tested shall be formed by pouring the molten 
material into a briquette mold. The dimensions of the briquette shall be 1 cm. 
(0.394 inch) in thickness throughout its entire length; distance between the clips or 
end pieces, 3 cm. (1.181 inches); width of asphalt cement section at mouth of clips, 
2 cm. (0.787 inch); width at minimum cross section, half way between clips, 1 cm. 
(0.394 inch). The centerpieces are removable, the briquette mold being held together 
during molding with a clamp or wire. 
The molding of the briquette shall be done as follows: The two center sections shall 
be well amalgamated to prevent the asphalt cement from adhering to them, and the 
briquette mold shall then be placed on a freshly amalgamated brass plate. The 
asphalt cement to be tested shall be poured into the mold while in a molten state, 
a slight excess being added to allow for shrinkage on cooling. When the asphalt 
cement in the mold is nearly cool, the briquette shall be cut off level, with a warm 
knife or spatula. When it is thoroughly cooled to the temperature at which it is 
desired to make the test, the clamp and the two sidepieces are removed, leaving the 
briquette of asphalt cement held at each end by the ends of the mold, which now 
play the part of clips. The briquette shall be kept in water for 30 minutes at 4° C. 
(39° F.) or 25° C. (77° F.) before testing, dependent on the temperature at which the 
ductility is desired. The briquette with the clips attached shall then be placed in 
a "ductility test machine " (fig. 26) rilled with water at one of the above temperatures 
to a sufficient height to cover the briquette not less than 50 mm. (1.969 inches). This 
machine consists of a rectangular water-tight box, having a movable block working 
on a worm gear from left to right. The left clip is held rigid by placing its ring over a 
short metal peg provided for this purpose ; the right clip is placed over a similar rigid 
peg on the movable block. The movable block is provided with a pointer which 
moves along a centimeter scale. Before starting the test, the centimeter scale is ad- 
justed to the pointer at zero. Power is then applied by the worm-gear pulling from 
left to right at the uniform rate of 5 cm. (1.969 inches) per minute. 
The distance, in centimeters, registered by the pointer on the scale at the time of 
rupture of the thread of asphalt cement shall be taken as the ductility of the asphalt 
cement. 
31. STANDARD METHOD FOR THE DISTILLATION OF TAR AND TAR 
PRODUCTS. 
(A. S. T. M. Standard Method, Serial Designation: D 20-18.) 
(1) The sample as received shall be thoroughly stirred and agitated, warming, if 
necessary, to insure a complete mixture before the portion for analysis is removed. 
(2) If the presence of water is suspected or known the material shall be dehydrated 
before distillation. About 500 c. c. of the material are placed in an 8'00-c. c. copper 
still provided with a distilling head connected with a water-cooled condenser (see 
