Abstract: The present invention relates to an instrument and methods for determining stability of oils and fats. The instrument includes a sample reaction vessel for containing a sample of an oil or fat, a moisturized gas source operably connected to the vessel for contacting a moisturized gas with the sample, a compound trap containing water operably connected to the vessel to contact the moisturized gas from the vessel with the water, and an automatic data acquisition and control system for monitoring the electrical conductivity of the water. The method is carried out by heating an oil or a fat, contacting the oil or fat with a moisturized gas, contacting the moisturized gas with water to form a trap solution, measuring the electrical conductivity of the trap solution, and determining the stability of the oil or fat.