16 - BULLETIN 314, U. S: DEPARTMENT OF AGRICULTURE. 
passes the upper arm of the wire, is inserted in one hole and the 
thermometer in the other. The bulb of the thermometer should be. 
just level with the cube and at an equal distance from the side of the . 
beaker. in order that a reading of the thermometer may be made, if . 
necessary, at the pomt which passes through the cover, the hole is 
made triangular in shape and covered with an ordinary object glass 
through which the stem of the thermometer may be seen. Readings 
made through this glass should be corrected for the angle of observa- 
tion, which may be made constant by always sighting from the front 
edge of the opening to any pie? point on the stem of the thermometer 
below the cover. 
After the test specimen has been placed i in the apparatus, the liquid 
in the outer vessel is heated in such a manner that the thermometer 
registers an increase of 5° C. per mmute. The temperature at which 
the bitumen touches a piece of paper placed in the bottom of the 
beaker is taken as the meltmg point. Determinations made in the - 
manner described should not vary more than 2° for different tests of 
the same material. At the beginning of this test the temperature of 
both bitumen and bath should be approximately 25° C. 
USE OF MELTING-POINT DETERMENATION. 
The melting-point determination should be made on all bituminous 
road binders sufficiently hard to be handled at room temperature after 
removing from the mold. This test is not usually required for 
bitumens which are to be cut-with a nonvolatile flux before use. 
DETERMINATION OF FLASH AND BURNING POINTS. 
CLOSED-CUP METHOD. 
EQUIPMENT. 
1 New York State Board of Health oil tester with Bunsen burner. (Fig. 9.) 
1 open-cup oil tester with Bunsen burner. (Fig. 10.) 
1 chemical thermometer reading from 0° ©. to 400° C. 
1 piece of 6-millimeter glass tubing, 6 centimeters in length, one end of which has 
been drawn to a 1-millimeter opening. Soft rubber tubing for gas connection. 
METHOD. 
While for all ordinary purposes the open-cup method of determining 
the flash and burning points of bituminous road materials is satisfac- 
tory, the closed-cup method described below is to be preferred, where 
greater accuracy is required. This is particularly true for materials 
of a relatively low flash point. 
The oil tester shown in figure 9 consists of a copper oul cup 4 of 
about 300 cubic centimeters capacity, which is heated in an oil. 
bath 6 by a small Bunsen flame. The cup is provided with a glass 
cover ¢, carrying a thermometer d, and a hole e for inserting the 
