16 BULLETIN 314, IT. S. DEPARTMENT OF AGKICULTUKE. 



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 readhig of the thermometer may be made, if 

 necessary, at the point 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 given point on the stem of the thermometer 

 below the cover. 



After the test specimen has been placed 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 minute. The temperature at which 

 the bitumen touches a piece of paper placed in the bottom of the 

 beaker is taken as the melting 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 DETERMINATION. 



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 witli Bunsen. burner. (Fig. 9.) 

 1 open-cup oil tester with Bunsen burner. (Fig. 10.) 

 1 chemical thermometer reading from 0° C. 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. 



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 oil cup a of 

 about 300 cubic centimeters capacity, which is heated in an oil 

 bath b by a small Bunsen flame. The cup is provided with a glass 

 cover c, carrying a thermometer d, and a hole e for inserting the 



