Designation:D1293−18StandardTestMethodsforpHofWater1ThisstandardisissuedunderthefixeddesignationD1293;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1ThesetestmethodscoverthedeterminationofpHbyelectrometricmeasurementusingtheglasselectrodeasthesensor.Twotestmethodsaregivenasfollows:SectionsTestMethodA—PreciseLaboratoryMeasurement8to15TestMethodB—RoutineorContinuousMeasurement16to241.2TestMethodAcoverstheprecisemeasurementofpHinwaterutilizingatleasttwoofsevenstandardreferencebuffersolutionsforinstrumentstandardization.1.3TestMethodBcoverstheroutinemeasurementofpHinwaterandisespeciallyusefulforcontinuousmonitoring.Twobuffersareusedtostandardizetheinstrumentundercontrolledparameters,buttheconditionsaresomewhatlessrestrictivethanthoseinTestMethodA.Foron-linemeasurement,alsoseeTestMethodD6569whichprovidesmoredetail.1.4BothtestmethodsarebasedonthepHscaleestablishedbyNIST(formerlyNBS)StandardReferenceMaterials.21.5NeithertestmethodisconsideredtobeadequateformeasurementofpHinwaterwhoseconductivityislessthanabout5µS/cm.RefertoTestMethodsD5128andD5464.1.6Precisionandbiasdatawereobtainedusingbuffersolutionsonly.Itistheuser’sresponsibilitytoassurethevalidityofthesetestmethodsforuntestedtypesofwater.1.7ThevaluesstatedinSIunitsaretoberegardedasstandard.Thevaluesgiveninparenthesesaremathematicalconversionstoinch-poundunitsthatareprovidedforinforma-tiononlyandarenotconsideredstandard.1.8Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafety,health,andenvironmentalpracticesanddeter-minetheapplicabilityofregulatorylimitationspriortouse.1.9Thisinternationalstandardwasdevelopedinaccor-dance...
