Designation:D971−12StandardTestMethodforInterfacialTensionofOilAgainstWaterbytheRingMethod1ThisstandardisissuedunderthefixeddesignationD971;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thistestmethodcoversthemeasurementoftheinter-facialtensionbetweenmineraloilandwater,undernon-equilibriumconditions.1.2Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D117GuideforSampling,TestMethods,andSpecificationsforElectricalInsulatingOilsofPetroleumOriginD923PracticesforSamplingElectricalInsulatingLiquidsD2285TestMethodforInterfacialTensionofElectricalInsulatingOilsofPetroleumOriginAgainstWaterbytheDrop-WeightMethod(Withdrawn2008)33.SummaryofTestMethod3.1InterfacialTensionisdeterminedbymeasuringtheforcenecessarytodetachaplanarringofplatinumwirefromthesurfaceoftheliquidofhighersurfacetension,thatis,upwardfromthewater-oilinterface.Tocalculatetheinterfacialtension,theforcesomeasurediscorrectedbyanempiricallydeterminedfactorwhichdependsupontheforceapplied,thedensitiesofbothoilandwater,andthedimensionsofthering.Measurementsaremadeunderrigidlystandardizednonequi-libriumconditionsinwhichthemeasurementiscompletedwithin60safterformationoftheinterface.4.SignificanceandUse4.1Interfacialtensionmeasurementsonelectricalinsulatingoilsprovideasensitivemeansofdetectingsmallamountsofsolublepolarcontaminantsandproductsofoxidation.Ahighvaluefornewmineralinsulatingoilindicatestheabsenceofmostundesirablepolarcontaminants.Thetestisfrequentlyappliedtoservice-agedoilsasanindicationofthe...
