1.1 This test method describes the detection of corrosive sulfur compounds (both inorganic and organic) in electrical insulating oils of petroleum origin. 1.2 New and in-service mineral insulating oils may contain substances that cause corrosion under certain conditions of use. This test method is designed to detect the presence of, or the propensity to form, free (elemental) sulfur and corrosive sulfur compounds by subjecting copper to contact with oil under prescribed conditions. 1.3 Two methods (A and B) have been introduced where historically there has only been one. Method A is the one that has been in place since 1953. Method B is more rigorous and the preferred method. 1.4 The values stated in SI units are to be regarded as the standard. Inch-pound units are included for informational purposes. This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.