1.1 ,This guide covers an apparatus used to measure the oxidation or thermal stability of liquids by subjecting them to temperatures in the range from 50 ,°,C to 375 ,°,C in the presence of air, oxygen, nitrogen, or other gases at flow rates of 1.5 ,L/h to 13 ,L/h, or in the absence of gas flow. Stability may be measured in the presence or absence of water or soluble or insoluble catalysts. Gases evolved may be allowed to escape, condensed and collected, or condensed and returned to the test cell.