Designation:D5128−14StandardTestMethodforOn-LinepHMeasurementofWaterofLowConductivity1ThisstandardisissuedunderthefixeddesignationD5128;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversthepreciseon-linedetermina-tionofpHinwatersamplesofconductivitylowerthan100µS/cm(seeTable1andTable2)overthepHrangeof3to11(seeFig.1),underfieldoperatingconditions.pHmeasure-mentsofwateroflowconductivityareproblematicforconventionalpHelectrodes,methods,andrelatedmeasurementapparatus.1.2ThistestmethodincludestheproceduresandequipmentrequiredforthecontinuouspHmeasurementoflowconduc-tivitywatersamplestreamsincludingtherequirementsforthecontrolofsamplestreampressure,flowrate,andtemperature.Foroff-linepHmeasurementsinlowconductivitysamples,refertoTestMethodD5464.1.3ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.4Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D1129TerminologyRelatingtoWaterD1193SpecificationforReagentWaterD1293TestMethodsforpHofWaterD2777PracticeforDeterminationofPrecisionandBiasofApplicableTestMethodsofCommitteeD19onWaterD3864GuideforOn-LineMonitoringSystemsforWaterAnalysisD4453PracticeforHandlingofHighPurityWaterSamplesD5464TestMethodforpHMeasurementofWaterofLowConductivity3.Terminology3.1Definitions—Fordefinitionsofothertermsusedinthistestmethod,refertoTerminologyD1129andPracticeD3864.3.2DefinitionsofTermsSpecifictoThisStandard:3.2.1liquidjunctionpotential,n—adcpotentialthatap-pearsatthepointofcontactbetweenthereferenceelectrode’ssaltbridge(sometimes...
