This test method covers measurement of the ability of petroleum oils or synthetic fluids to separate from water. Although developed specifically for steam-turbine oils having viscosities of 28.8–90 mm2/s at 40°C, this test method may be used to test oils of other types having various viscosities and synthetic fluids at other test temperatures. It is recommended, however, that the test temperature be raised to 82 6 1°C when testing products more viscous than 90 mm2/s at 40°C. For higher viscosity oils where there is insufficient mixing of oil and water, the standard mentioned 2/4 is recommended. Other test temperatures such as 25°C may also be used. A 1% sodium chloride (NaCl) solution or synthetic seawater may be used in place of distilled water when testing certain oils or fuels used in marine applications. 1/2 When testing synthetic fluids whose relative densities are greater than that of water, the procedure is unchanged, but it should be noted that the water will probably float on the emulsion or liquid. 1/3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1/4 This standard does not purport to address all of 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. For specific warning statements, see Section 6.