250 mL of oil sample was heated at 250 C for periods of 5 h.
The temperature was adjusted by calibrated thermometer.
Although these oils are not usually submitted to such high temperatures
it has been selected as a model system in which the evolution
of selected aldehydes under these conditions may be clearly
observed. Throughout the heating process cover flask was open.
At the end of heating the hot plate was turned off and the oil reach
to the ambient temperature, then oil samples refrigerated until
their study in order to avoid or hinder the continuation of the
degradation process.