1882. 141 Trans. N. Y. Ac. Sci. 
quantity of the oil to be tested is introduced, the cap with the wicks is 
fitted, and the whole is placed in a vessel of water of the temperature 
at which the oil should zo¢ flash. When this temperature is nearly 
reached, the little wick on the side of the cap is lighted ; and when the 
thermometer reaches the standard temperature, a measured quantity 
of water is poured into the narrow limb of the U tube. By this action 
the level of the oil in the enlarged portion of the tube is raised, and 
any vapors that may be there are forced through the tubes around the 
central jet. These vapors meet the flame of the jet already lighted, 
they become ignited, and by so doing ignite the central wick. 
It will be seen that as soon as the oil-level is raised, it is not easy to 
repeat the experiment ; hence the apparatus is only intended to deter- 
mine at what temperature an oil does zo/ give off vapors, and not to 
determine its flashing point. One important difficulty in this apparatus 
is the fact that the central wick will not ignite with certainty every 
time that an oil is giving off inflammable vapors. For I have repeat- 
edly failed to ignite the central wick in an experiment, and on remov- 
ing the cap have immediately obtained a flash with the oil in the cup. 
When the central wick ignites, this apparatus gives results that are 
generally higher than with open testers, which may be due to the fact 
that the vapors must have a certain density before their ignition will 
inflame the central jet. 
One of the best of the recently devised forms of ‘‘ closed testers ” is 
that used in the State of Wisconsin. Its construction is very simpie, 
but it embodies some features that make it stand before those I have 
already mentioned. It consists of a copper water-bath, a copper oil 
vessel, and a cover with two holes in it, through one of which passes a 
thermometer. 
The oil-cup holds a good quantity of oil, and there is considerable 
space above the oil-surface for the accumulation of the vapors. Its use 
is very simple, and consists in heating the oil slowly by means of the 
water, the flash being obtained by introducing a small flame into the 
second hole of the cover. Theapparatus is not costly ; it is easily used 
and cleaned, and the results obtained are quite near the truth. 
Some years ago Mr. MANN conceived the idea that the best way to 
test oi] is under the same conditions that obtain in using it. For this 
purpose he devised a metallic lamp, about the same size as an ordinary 
kerosene one; he replaced the usual wick-holder by a tube, which 
could be loosely closed with a plug. The side of the lamp contained a 
valve opening inwards, through which a flame could be introduced to 
ignite the vapors. The thermometer was placed in a c'osed tube fitted 
into the side cf the lamp. This lamp was placed in a water-bath that 
fitted it, and the whole heated slowly. A small flame (a gas-jet) was 
