With extremely dark oils, operate
the pump slowly and lower it so that the delivery tube nearly
touches the top of the light well, so as to obtain a continuous
film thin enough to permit observation of the aniline point.
Adjust the voltage on the lamp until just enough light is given
for the filament to be visible through the film. Raise the
temperature of the mixture at a rate of 1 to 2°C (2.0 to
3.5°F)/min until the aniline point has just been passed