SPECIFICATIONS FOE BITUMINOUS ROAD MATEEIALS. 
49 
y— 
»o 
.i 
— a 
— c 
pointed hardwood stopper d. Pointed metal projections are placed on the 
inside of a at equal distances from the bottom and serve for measuring the 
charge of material, which is 240 cubic centimeters. The thermometer e is used 
to ascertain the temperature of the material to be tested. The vessel a is 
surrounded by a brass jacket /, which holds the material used as a heating 
bath, either water or cottonseed oil, according to the temperature at which 
the test is to be made. A tripod g serves as a support for the apparatus 
and also carries a ring burner h by means of which the bath is directly 
heated. The measuring cylinder of 100 cubic centimeters capacity, which is 
sufficiently accurate for work with road materials, is placed directly under the 
outflow tube. 
As all viscosity deter- 
minations should be com- 
pared with that of water 
at 25° C, the apparatus 
should be previously cali- 
brated as follows: The 
cup and outlet tube 
should first be scrupu- 
lously cleaned. A piece 
of soft tissue paper is 
convenient for cleaning 
the latter. The stopper 
is then inserted in the 
tube and the cup filled 
with water at 25° C. to 
the top of the projections. 
The measuring cylinder 
should be placed directly 
under the outflow tube so 
that the material, upon 
flowing out, will not 
touch the sides, and the 
stopper may then be re- 
moved. The time required for 50 cubic centimeters to run out should be ascer- 
tained by means of a stop watch and the results so obtained should be checked 
a number of times. The time should be about 11 seconds, 
Bituminous road materials are tested ia the same manner as water and the 
temperature at which the test is made is controlled by the bath. The material 
should be brought to the desired temperature and maintained there for at 
least three minutes before making the test. The results are expressed as 
specific viscosity compared with water at 25° C, as follows : 
Specific viscosity at a° C. = seconds for passage of given volume at a° C 
seconds for passage of same volume of water at 25 C. 
^ 
Fig, 3.—*En§ler yigeosimeter. 
VOLATILIZATION TEST. 
[Bulletin 314, p. 19.] 
The oven shown in figure 4, known as the New York testing laboratory oven, 
is used by the office of public roads and rural engineering, although any other 
form may be used that will give a uniform temperature throughout all parts 
where samples are placed. The bulb of one of the termometers is immersed 
