18 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 filling the oil cup 
with the material under examination to within 
about 5 millimeters of the top. The Bunsen 
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 cil shows that the flash point is reached 
and the temperature at this point istaken. It 
will usually be found that the flash pomt 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- 
| H—C tained by continuing the test and noting that 
| temperature at which it ignites and burns. 
ey A Trnfinnfenfeanfnfcapunfunpunjunfvufaapunfunfonfuafanfmafunficaponfapiafuafinsfanfanpnafany 
| The flame should then be extinguished by 
: means of a metal cover supplied with the in- 
strument. ’ 
USE OF FLASH-POINT AND BURNING-POINT 
ex DETERMINATIONS. 
f = i \ 
a The flash and burning point deter- 
3 : minations should be made on all bi- 
= i) 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. 
