SAMPLING AND TESTING HIGHWAY MATERIALS. 57 
throughout the test he allowed to vary more than 0.5° C. from the 
temperature specified. 
(b) After the material to be tested has been kept in the ice 
water for not less than 15 minutes nor more than 20 minutes, the 
collar with its contents shall be removed from the plate and 
screwed into the aluminum float and immersed in water at 5° C. 
for 1 minute. Any water shall then be removed from the inside 
of the float and the latter immediately floated in the warm bath. 
As the plug of material becomes warm and fluid, it is forced up- 
ward and out of the collar until the water gains entrance into the 
saucer and causes it to sink. 
(c) The time in seconds between the placing of the apparatus 
on the water and the instant when the water breaks through the 
material shall be determined by means of a stop watch, and shall 
be taken as a measure of the consistency of the material under 
examination. 
Note. — Special precaution should be taken to insure the collar fit- 
ting tightly into the float and to see that there is no seepage of 
water between the collar and float during the test. 
TEST FOR SOFTENING POINT OF BITUMINOUS MATE- 
RIALS (RING-AND-BALL METHOD). 
(A. S. T. M. standard method, serial designation D 36-21, slightly 
modified.) 
1. The softening of bituminous materials generally takes place 
at no definite moment or temperature. As the temperature rises, 
they gradually and imperceptibly change from a brittle or ex- 
ceedingly thick and slow-flowing material to a softer and less 
viscous liquid. For this reason the determination of the soften- 
ing point must be made by a fixed, arbitrary, and closely de- 
fined method if the results obtained are to be comparable. 
I. APPARATUS. 
2. The apparatus shall consist of the following: Brass ring. 
(a) A brass ring 15.875 millimeters (five-eight inch) in inside 
diameter and 6.35 millimeters (one-quarter inch) deep; thick- 
ness of wall, 2.38 millimeters (three thirty-second inch) ; per- 
missible variation of inside diameter and thickness of ring, 0.25 
millimeters (0.01 inch). This ring shall be attached in a con- 
venient manner to a No. 13 B. & S. gauge brass wire (diameter 
1.83 millimeters=0.0720 inch ) . (See fig. 3. ) 
(b) A steel ball 9.53 millimeters (three-eighth inch) in diam- Steel ball. 
eter weighing between 3.45 and 3.55 grams. 
(c) A glass vessel, capable of being heated, not less than Vessel. 
8.5 centimeters (3.34 inches) in diameter and measuring 10.5 
centimeters (4.13 inches) in depth from the bottom of the flare. 
(A GOO cubic centimeter beaker, low form, meets this require- 
ment.) 
(d) A thermometer which shall conform to the following Thermometer. 
specifications : 
Total length: 370 to 400 milimeters (14.57 to 15.75 inches). 
Diameter: 6.5 to 7.5 millimeters (0.0256 to 0.295 inch). 
Bulb length: Not over 14 millimeters (not over 0.55 inch). 
Bulb diameter: 4.5 to 5.5 millimeters (0.177 to 0.217 inch). 
The scale shall be engraved upon the stem of the thermometer, 
shall be clear-cut and distinct, and shall run from 0° to 80° C. 
(32° to 176° F.) in 0.2° C. divisions. It shall commence not less 
than 7.5 centimeters (2.95 inches) above the bottom of the bulb. 
The thermometer shall be furnished with an expansion chamber 
at the top and have a ring for attaching tags. It shall be made 
of a suitable quality of glass and shall be so annealed as not 
to change its readings under conditions of use. It shall be 
correct to 0.25° C. (0.45° F.) as determined by comparison at 
full immersion with a similar thermometer calibrated at full 
immersion by the United States Bureau of Standards. 
