BULLETIN" 314, U. S. DEPARTMENT OF AGRICULTURE. 



thermometer c is suspended from the wire support d directly over the 

 center of the cup so that its bulb is entirely covered with oil but does 

 not touch the bottom of the cup. The testing 

 flame is obtained from a jet of gas passed 

 through a piece of glass tubing, and should be 

 about 5 millimeters in length. 



The test is made by first rilling the oil cup 

 with the material under examination to within 

 about 5 millimeters of the top. The Buns en 

 flame is then applied in such a manner that 

 the temperature of the material in the cup is 

 raised at the rate of 5°C. per minute. From 

 time to time the testing flame is brought almost 

 in contact with the surface of the oil. A dis- 

 tinct flicker or flash over the entire surface of 

 the oil shows that the flash point is reached 

 and the temperature at this point is taken. It 

 will usually be found that the flash point as 

 determined by the open-cup method is some- 

 what higher than by the closed-cup method, 

 for the same material. 



The burning point of the material is ob- 

 tained by continuing the test and noting that 

 temperature at which it ignites and burns. 

 The flame should then be extinguished by 

 means of a metal cover supplied with the in- 

 strument. 



USE OF FLASH-POINT AND BURNING-POINT 

 DETERMINATIONS. 



The flash and burning point deter- 

 minations should be made on all bi- 

 tuminous road materials which have 

 to be heated before application and 

 upon all fluid and semisolid products 



Fig. 10. — Open-cup oil tester. 



which show a loss by the volatilization test at 163° C. of over 5 per 

 cent. It should also be made upon fluxes which are to be used in 

 cutting hard bitumens. 



