10 BULLETIN 314, U. 8. DEPARTMENT OF AGRIOULTURE. 
this bath for at least 15 mmutes. Meanwhile the other cup is filled 
-about three-fourths full of water and placed on the tripod, and the 
water is heated to any desired temperature at which the test is to 
be made. This temperature should be accurately maintained, and 
should at no time throughout the entire test be allowed to vary 
more than one-half a degree centigrade from the temperature selected. 
After the material to be tested has been kept in the ice water for at 
least 15 minutes, the collar with its contents is removed from the 
plate and screwed into the aluminum float, which is then immediately 
floated in the warmed bath. As the plug of bitumimous material 
Fre. 5.—New York testing laboratory float apparatus. 
becomes warm and fluid, it is gradually forced upward and out of the 
‘collar, until water gams entrance to the saucer and causes it to sink. 
The time in seconds between placing the apparatus on the water 
and when the water breaks through the bitumen is determined by 
means of a stop watch and is taken as a measure of the consistency 
of the material under examination. - 
USE O¥ THE FLOAT TEST. 
This test is always made on viscous and semisolid refined tars, 
and often on the viscous and semisolid petroleum and asphalt prod- 
ucts, although, when the penetratien test can be employed on the 
two latter classes of material, the float test is not always considered 
necessary. For the more fluid products the test is made at 32° C. 
and for the semisolid materials, at 50° C. When the material under 
examination is quite hard, the test may be run at 100° C. 
