ASTM D 1125-95 水的电导率和电阻率测定的标准方法

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Designation:D1125–95(Reapproved2009)

StandardTestMethodsfor

ElectricalConductivityandResistivityofWater1

Thisstandardisissuedunderthe xeddesignationD1125;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.

1.Scope

D2186TestMethodsforDeposit-FormingImpuritiesin1.1ThesetestmethodscoverthedeterminationoftheSteam

electricalconductivityandresistivityofwater.ThefollowingD2777PracticeforDeterminationofPrecisionandBiasoftestmethodsareincluded:

ApplicableTestMethodsofCommitteeD19onWaterRangeSectionsD3370PracticesforSamplingWaterfromClosedConduitsTestMethodA—FieldandRoutineLaboratory10to200000

12to18

D4519TestMethodforOn-LineDeterminationofAnionsMeasurementofStatic(Non-Flowing)µS/cmSamples

andCarbonDioxideinHighPurityWaterbyCationTestMethodB—ContinuousIn-LineMeasure5to200000

19to23

ExchangeandDegassedCationConductivity

ment

µS/cm

D5391TestMethodforElectricalConductivityandResis-1.2Thesetestmethodshavebeentestedinreagentwater.IttivityofaFlowingHighPurityWaterSample

istheuser’sresponsibilitytoensurethevalidityofthesetestE1Speci cationforASTMLiquid-in-GlassThermometersmethodsforwatersofuntestedmatrices.

1.3Formeasurementsbelowtherangeofthesetestmeth-3.Terminologyods,refertoTestMethodD5391.

3.1De nitions:

1.4ThevaluesstatedinSIunitsaretoberegardedas3.1.1electricalconductivity—thereciprocalofthea-cre-standard.Nootherunitsofmeasurementareincludedinthissistanceinohmsmeasuredbetweenoppositefacesofastandard.

centimetrecubeofanaqueoussolutionataspeci edtempera-1.5Thisstandarddoesnotpurporttoaddressalloftheture.

safetyconcerns,ifany,associatedwithitsuse.ItistheNOTE1—Theunitofelectricalconductivityissiemenspercentimetre.responsibilityoftheuserofthisstandardtoestablishappro-(Thepreviouslyusedunitsofmhos/cmarenumericallyequivalenttopriatesafetyandhealthpracticesanddeterminetheapplica-S/cm.)Theactualresistanceofthecell,Rx,ismeasuredinohms.Thebilityofregulatorylimitationspriortouse.

conductance,1/Rx,isdirectlyproportionaltothecross-sectionalarea,A(incm2),andinverselyproportionaltothelengthofthepath,L(incm):

2.ReferencedDocuments1/Rx5K·A/L

2.1ASTMStandards:2

TheconductancemeasuredbetweenoppositefacesofaD1066PracticeforSamplingSteamcentimetrecube,K,iscalledconductivity.ConductivityvaluesD1129TerminologyRelatingtoWater

areusuallyexpressedinmicrosiemens/centimetreorinD1192GuideforEquipmentforSamplingWaterandsiemens/centimetreataspeci edtemperature,normally25°C.SteaminClosedConduits3

3.1.2electricalresistivity—thea-cresistanceinohmsmea-D1193Speci cationforReagentWater

suredbetweenoppositefacesofacentimetrecubeofanaqueoussolutionataspeci edtemperature.

1

ThesetestmethodsareunderthejurisdictionofCommitteeD19onWaterandNOTE2—Theunitofelectricalresistivityisohm-centimetre.TheactualarethedirectresponsibilityofSubcommitteeD19.03onSamplingWaterandresistanceofthecell,Rx,ismeasuredinohms,andisdirectlyproportionalWater-FormedDeposits,AnalysisofWaterforPowerGenerationandProcessUse,tothelengthofthepath,L(incm),andinverselyproportionaltotheOn-LineWaterAnalysis,andSurveillanceofWater.

CurrenteditionapprovedMay1,2009.PublishedJune2009.Originallycross-sectionalarea,A(incm2):

stpreviouseditionapprovedin2005asD1125–95(2005).Rx5R·L/A

2

ForreferencedASTMstandards,visittheASTMwebsite,,orcontactASTMCustomerServiceatservice@.ForAnnualBookofASTMTheresistancemeasuredbetweenoppositefacesofacenti-Standardsvolumeinformation,refertothestandard’sDocumentSummarypageonmetrecube,R,uallyexpressedinohm·centimetre,orinmegohm·centime-3

.

tre,ataspeci edtemperature,normally25°C.

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TABLE1ElectricalConductivityValuesAssignedtothePotassiumChlorideintheReferenceSolutionA

ReferenceSolution

A

ApproximateNormalityofSolution

1

MethodofPreparation

74.2460gofKClweighedinairper1Lof

solutionat20°C7.4365gofKClweighedinairper1Lof

solutionat20°C0.7440gofKClweighedinairper1Lof

solutionat20°CDilute100mLofSolutionCto1Lat20°C

Tempera-ture,°C

01825018250182501825

ElectricalConductivity,µS/cm651769783811134271381116712856773.61220.51408.877.69B127.54B146.93

B0.1

C0.01

D0.001

Excludingtheconductivityofthewaterusedtopreparethesolutions.(See7.2andSection14.)Thesetabulatedconductivityvaluesareininternationalunits.Whenusingmeasuringinstrumentscalibratedinabsoluteunits,multiplythetabularvaluesby0.999505.B

FromGlasstone(13)

.

A

3.1.3Forde nitionsofothertermsusedinthesemethods,refertoTerminologyD1129.3.2Symbols:

3.2.1SymbolsusedintheequationsinSections14and16arede nedasfollows:J=cellconstant,cm 1,

K=conductivityat25°C,µS/cm,Kx=measuredconductance,S,

K1=conductivityoftheKClinthereferencesolutionatthetemperatureofmeasurement(Table1),µS/cm,

K2=conductivityofthewaterusedtopreparethereferencesolution,atthesametemperatureofmeasurement,µS/cm,Q=temperaturecorrectionfactor(seeSection11),R=resistivityat25°C,ohm·cm,Rx=measuredresistance,ohm.

4.Signi canceandUse

4.1Thesetestmethodsareapplicableforsuchpurposesasimpuritydetectionand,insomecases,thequantitativemea-surementofionicconstituentsdissolvedinwaters.Theseincludedissolvedelectrolytesinnaturalandtreatedwaters,suchasboilerwater,boilerfeedwater,coolingwater,andsalineandbrackishwater.

4.1.1Theirconcentrationmayrangefromtracelevelsinpurewaters(1)4tosigni cantlevelsincondensedsteam(seeTestMethodsD2186andD4519,andRef(2)),orpuresaltsolutions.

4.1.2Wheretheprincipalinterestintheuseofconductivitymethodsistodeterminesteampurity,seeRef(3).Thesetestmethodsmayalsobeusedforcheckingthecorrectnessofwateranalyses(4).

5.Interferences

5.1Exposureofasampletotheatmospheremaycausechangesinconductivity/resistivity,duetolossorgainofdissolvedgases.Thisisextremelyimportantinthecaseofverypurewaterswithlowconcentrationsofdissolvedionizedmaterials.Thecarbondioxide,normallypresentintheair,candrasticallyincreasetheconductivityofpurewatersbyapproxi-Theboldfacenumbersinparenthesesrefertoalistofreferencesattheendofthisstandard.

--`,,```,,,,````-`-`,,`,,`,`,,`---

mately1µS/cm.Contactwithairshouldbeavoidedbyusing ow-throughorin-linecellwherefeasible.Chemicallypureinertgases,suchasnitrogenorhelium,maybeusedtoblanketthesurfaceofsamples.

5.2Undissolvedorslowlyprecipitatingmaterialsinthesamplecanformacoatingontheelectrodesoftheconductivitycellthatmaycauseerroneousreadings.Forexample,biofoul-ingofthecellorabuild-upof lmingaminesmaycausepoorcellresponse.Inmostcasestheseproblemscanbeeliminatedbywashingthecellswithappropriatesolvents.

5.3Ifanunshieldedcellisusedtomeasuretheresistivity/conductivityofhighresistivitywaterthereisapossibilityofelectricalpickupcausingerroneousreading.Forthisreasonitisrecommendedthatconductivitycellsforthisapplicationbeofcoaxialshieldedtypeorequivalent,andthatthecablesandinstrumentalsobeshielded.

6.Apparatus

6.1MeasuringCircuit—Theinstrumentmaybeamanuallyoperatedwheatstonebridgeortheequivalent,oradirectreadinganalogordigitalmeter.Instrumentsshallenergizetheconductivitycellwithalternatingcurrentand,togetherwiththecellandanyextensionleadwire,shallbedesignedtoreduceerrorsfromthefollowingsources:

6.1.1Inhighlyconductivesolutions—Uncompensatedelec-trodepolarizationduetoexcessivecurrentdensityattheelectrodesurfacescancausenegativeconductivityerrors.Insufficientseriescapacitanceattheelectrode/solutioninter-facecanallowchargingeffectstodistortthea-cmeasurementandcauseerrorsifnotcompensated.Leadwireresistancecanaddsigni cantlytothemeasuredresistance.

6.1.2Inlowconductivitysolutions—Excessiveparallelca-pacitanceinthecellandextensionleadwirecanshuntthemeasurementandcausepositiveconductivityerrors.Tempera-turecompensationerrorscanbesigni cantbelow5µS/cmifvariablecoefficientalgorithmsarenotemployedasdescribedinTestMethodD5391.

6.1.3Thesesourcesoferrorareminimizedbyanappropri-atecombinationofa-cdrivevoltage,waveshape,frequency,phasecorrection,wavesamplingtechniqueandtemperaturecompensationdesignedinbytheinstrumentmanufacturer.Theinstrumentmanufacturer’srecommendationsshallbefollowed

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TABLE2RecommendedCellConstantsforVariousConductivity

Ranges

RangeofConductivity,µS/cm

0.05to1010to200200to5000

5000to1000000

CellConstant,cm 1

0.01to0.10.1to11to1010to

100

inselectingthepropercellconstant,leadwiresize,andlengthandmaintenanceoftheelectrodesurfaceconditionfortherangeofmeasurement.Calibrationmaybeineitherconduc-tivityorresistivityunits.

6.1.4Whenanoutputsignalisrequiredfromanon-lineinstrument,itshallbeelectricallyisolatedfromthecelldrivecircuittopreventinteractionbetweenasolutiongroundatthecellandanexternalcircuitground.6.2Cells:

6.2.1Flow-throughorin-linecellsshallbeusedformea-suringconductivitieslowerthan10µS/cm(resistivitieshigherthan100000ohm·cm),toavoidcontaminationfromtheatmosphere.However,sampleswithconductivitygreaterthan10µS/cmmayalsobemeasured.Inallothercases,pipet-typeordipcellscanalsobeused.Pipetordipcellsmaybeusedtomeasuresamplesintherangeof1to10µS/cmifthesampleisprotectedbyaninertgaseouslayerofnitrogenorhelium.6.2.2Acellconstantshallbechosenwhichwillgiveamoderatecellresistance,matchingtheinstrumentmanufactur-er’srequirementsfortherangeofmeasurement.Forlaboratorybridges,Table2providesconservativeguidelines.

6.2.3Flow-throughandin-linecellsshallbemountedsothatcontinuous owofthesamplethroughorpastitispossible.Flowrateshouldbemaintainedataconstantrateconsistentwiththemanufacturer’srecommendationsforthecellbeingused,particularlyatconductivitiesbelow10µS/cm.Thecellshallretaincalibrationunderconditionsofpressure, ow,andtemperaturechange,andshallexcludetheatmo-sphereandbeconstructedofcorrosionresistant,chemicallyinertmaterials.Thechamberorcellshallbeequippedwithmeansforaccuratemeasurementofthetemperature.

6.2.4Platinizedcellsshallnotbeusedformeasurementofconductivitiesbelow10µS/cm,exceptthatatraceor ashofplatinumblackmaybeusedoncellsformeasurementsintherangeof0.1to10µS/cm(see9.4).Becauseofthecostandfragilityofplatinumcells,itiscommonpracticetousetitanium,monel,andgraphiteelectrodesformeasurementswithaccuraciesontheorderof1%.Notethattheseelectrodesmayrequirespecialsurfacepreparation.Titaniumandmonelelectrodesareespeciallysuitableforhighresistancesolutionssuchasultrapurewater,butmayintroduceasmallsurfaceresistancewhichlimitstheiraccuracywhenthemeasuredresistanceislessthanafewthousandohms(1).

6.2.5Itisrecommendedthatcellsintendedforthemeasure-mentofconductivitiesbelow10µS/cmbereservedexclusivelyforsuchapplications.

6.3TemperatureProbes:

6.3.1ForTemperatureControl—Themeasurementoftem-peratureisnecessaryforcontrolofatemperaturebath,manualcompensation,orautomatictemperaturecompen---`,,```,,,,````-`-`,,`,,`,`,,`---

sation,orallofthese.Thermometers,thermistors,andresis-tancetemperaturedetectorswithaccuraciesof60.1°Corbetterareacceptableforthisapplication.AnASTMprecisionthermometer,Number63C,asde nedinSpeci cationE1,isrecommended.ThecalibrationoftemperatureprobesshouldbecheckedperiodicallybycomparisontoareferencetemperatureprobewhosecalibrationistraceabletotheU.S.NationalInstituteofScienceandTechnology(formerlyNBS)orequiva-lent.

6.3.2ForTemperatureCorrection—Athermometeraccu-rateto0.1°Cisacceptableforthisapplication,whentheinstrumentisnotprovidedwithmanualorautomatictempera-turecompensation.(SeeSection11).

7.Reagents

7.1PurityofReagents—Reagentgradechemicalsshallbeusedinalltests.Unlessotherwiseindicated,itisintendedthatallreagentsshallconformtothespeci cationsoftheCommit-teeonAnalyticalReagentsoftheAmericanChemicalSociety,wheresuchspeci cationsareavailable.5Othergradesmaybeused,provideditis rstascertainedthatthereagentisofsufficientlyhighpuritytopermititsusewithoutlesseningtheaccuracyofthedetermination.

7.2PurityofWater—Unlessotherwiseindicated,referencestowatershallbeunderstoodtomeanreagentwaterconformingtoSpeci cationD1193,TypeI.Inmakingupthepotassiumchloridesolutionsforcellconstantdeterminations,usewaterofconductivitynotgreaterthan1.5µS/cm.Ifnecessary,stabilizetothelaboratoryatmospherebyaspiratingairthroughthewaterfromafrittedglassorstainlesssteelgasdispersiontube.Theequilibriumpointisreachedwhentheconductivityre-mainsconstantbutnotgreaterthan1.5µS/cm.TheequilibriumconductivitymustbeaddedtoTable1.

7.3Alcohol—95%ethylalcohol.Alternatively,useisopro-pylalcoholormethylalcohol.

7.4AquaRegia(3+1)—Mix3volumesofconcentratedhydrochloricacid(HCl,spgr1.19)with1volumeofconcen-tratednitricacid(HNO3,spgr1.42).Thisreagentshouldbeusedimmediatelyafteritspreparation.7.5EthylEther.

7.6HydrochloricAcid(spgr1.19)—ConcentratedHCl.7.7HydrochloricAcid(1+1)—Mix1volumeofconcen-tratedHCl(spgr1.19)with1volumeofwater.

7.8PlatinizingSolution—Dissolve1.5gofchloroplatinicacid(H2PtCl6·6H2O)in50mLofwatercontaining0.0125gofleadacetate(Pb(C2H3O2)2).

7.9PotassiumChloride(KCl)—Theassayofthepotassiumchloridemustbe100.060.1%.ThisstandardizationgradeofKClisavailablefromNISTandfromcommercialsources.Dryat150°Cfor2horuntilweightlossislessthan0.02%;storeindesiccator.

//^:^^#^~^^""~:""~:$:@@:"#:$@^~:~**^"^~~"^~:^^::*#^#$\\

ReagentChemicals,AmericanChemicalSocietySpeci cations,AmericanChemicalSociety,Washington,DC.ForsuggestionsonthetestingofreagentsnotlistedbytheAmericanChemicalSociety,seeAnalarStandardsforLaboratoryChemicals,BDHLtd.,Poole,Dorset,U.K.,andtheUnitedStatesPharmacopeiaandNationalFormulary,U.S.PharmaceuticalConvention,Inc.(USPC),Rockville,MD.

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7.10PotassiumChlorideReferenceSolutionA—Dissolve74.2460gofKCl(weighedinair)inwateranddiluteto1Lat2062°CinaClassAvolumetric ask.

7.11PotassiumChlorideReferenceSolutionB—Dissolve7.4365gofKCl(weighedinair)inwateranddiluteto1Lat2062°CinaClassAvolumetric ask.

7.12PotassiumChlorideReferenceSolutionC—Dissolve0.7440gofKCl(weighedinair)inwaterandtodilute1Lat2062°CinaClassAvolumetric ask.

7.13PotassiumChlorideReferenceSolutionD—Dilute100mLofreferencesolutionCto1Lwithwaterat2062°CinaClassAvolumetric askshortlybeforeusing.Storethesolutioninaglass-stopperedbottleofchemicallyresistantglasswhichhasonlybeenusedforstorageofthissolution.

//^:^^#^~^^""~:""~:$:@@:"#:$@^~:~**^"^~~"^~:^^::*#^#$\\

NOTE3—TheelectricalconductivityofeachofthereferencedsolutionsisgiveninTable1.ThevaluesforelectricalconductivitiesforthesolutionsarethoseofG.JonesandB.C.Bradshaw(5),con rmedin1987(6)and1989(7)bytheNationalInstituteofStandardsandTechnology(NIST).ThedataofT.Shedlovsky(8)areusedforSolutionD.SolutionsA,B,andCwerepreparedbyJonesandBradshawusingthemolalordemalbasisbydissolving71.1352,7.4191,and0.7453g,respectively,ofKCl(invacuum)per1000gofsolution(invacuum).ThemethodofpreparationgiveninTable1includesthecorrectionstoweightsofKCl(inairagainstbrassweights)perlitreofsolutionsat20°CandassumesthedensityofKCl=1.98,densityofbrass=8.4,andthedensityofair=0.00118.Thedensitiesof1.0N,0.10N,and0.010NKClat20°C,1.04420,1.00280,and0.99871g/mL,respectively,wereinterpolatedfromthedataintheInternationalCriticalTables(9).

Aftercleaning,thoroughly ushthecellwithwater.Iftheoldplatinumblackcoatingistoberemoved,judiciousapplicationofaquaregiatotheelectrodes,orelectrolysisinHCl(spgr1.19)isfrequentlysuccessful.

9.3PlatinizetheelectrodesofthecellwithH2PtCl6solu-tion.Asuitableplatingapparatusconsistsofa6volta-csupply,avariableresistor,milliammeter,andanelectrode.Thedepositshouldpresentablack,velvetyappearanceandshouldadherewelltotheelectrodesurface.Theprocedureforplatinizingisnotcritical.Followthemanufacturer’sinstructionsorthefollowingguidelines.Goodplatinizedcoatingsareobtainedusingfrom1.5to3coulombs/cm2ofelectrodearea.Forexample,foranelectrodehavingatotalarea(bothsides)of10cm2,theplatingtimeatacurrentof20mAwouldbefrom121 2to25min.Thecurrentdensitymaybefrom1to4mA/cm2ofelectrodearea.Platetheelectrodesoneatatimewiththeaidofanextraelectrode.Duringtheplating,agitatethesolutiongently,oruseultrasonicbath.Whennotinuse,platinizedcellsshouldbe lledwithwatertopreventthedryingoutofelectrodeswhileinstorage.

9.4Formeasurementofconductivitiesintherangeof0.1to10µS/cm,atraceor ashcoatingofplatinumblackmaybeused.Fora ashcoating,thecellisleftintheplatinicchloridesolutionforonly2or3satacurrentofabout20mA.A ashcoatingwillleavetheelectrodeswiththeirmetallicappear-ance,butwithafaintblackishtint.

10.Calibration

10.1MeasuringInstrument—Acalibratingresistortobeusedinplaceoftheconductivitycellmaybefurnishedbythemanufacturer,togetherwithinformationastothecorrectscalereadingtheinstrumentshallassumewhenthisresistorisconnectedinplaceoftheconductivitycell.Followthemanu-facturer’sinstructionsandperiodicallychecktheinstrument.Alternatively,standardresistorswithcerti edaccuracyof60.05%maybeusedwithappropriatecalculationsadaptedtotheinstrumentscale.Someinstrumentsmaybefactorycali-brated,takingintoaccounttheresistanceofthecablewireattachedtotheconductivitycell;thismaybeindicatedbyawarningtoavoidcuttingorextendingthecablelength.Whenleadwiresbetweentheinstrumentandthecellarelong,checktheinstallationatleastoncebyconnectingthecalibratingresistoratthefarendoftheleadwireandnotingthedifference,ifany,inreadingwiththelongleadwireinthecircuit.Checkportableormanuallyoperatedinstrumentsinasimilarmannerwithoneorseveralcalibratingresistors.Noteerrorsofsigni -cantmagnitudeandcorrectsubsequentconductivityreadings.Calibrationchecksshouldbemadeatvaluesascloseaspossibletotheconductivityvaluesexpectedinsamples.Thisisespeciallyimportantifthemeasurementismadeattheextremehighorlowendofaninstrument’srange.Instrumentssub-jectedto eldusemayrequiremorefrequentchecksofcalibration.Fordirectreadinginstruments,theconductivitycheckresistanceinohmsequalsthecellconstant(cm 1)dividedbytheconductivitydesired(S/cm)whiletheresistivitycheckresistanceequalscellconstant(cm 1)timestheresis-tivitydesired(ohm·cm).

10.2ConductivityCells—For eldandroutinelaboratorytesting,thecalibrationofconductivitycellsmaybechecked

by

4

8.Sampling

8.1SamplesshallbecollectedinaccordancewithPracticeD1066,Speci cationD1192,andPracticesD3370,asappli-cable.

8.2Avoidexposureofthesampletoatmospherescontainingammoniaoracidicgases.Protectthesampletoavoidgainorlossofdissolvedgases,particularlyifthereissomedelaybeforetheconductivitymeasurementsaremade.Preferably,usea ow-typecellforsamplingandmeasuringcondensedsteamorwaterhavingaconductivityoflessthan10µS/cm.Forwatersintherangeof5to10µS/cm,adip-typecellmaybeusedifalayerofchemicallypurenitrogenorheliumismaintainedoverthesurface.

9.PreparationofElectrodes

9.1Ifthecellconstantascheckeddoesnotfallwithinreasonablelimitsofitsnominalvalue,itisnecessarytocleanorreplatinizetheelectrodesorreplacethecell.Ingeneral,nomechanicalcleaningshouldbeattempted.Inhighpuritywatermeasurements,wherethepresenceof nelydividedplatinumisundesirableduetoitslongretentionofimpurities,platini-zationofelectrodesshouldbeomitted,especiallyfortestingofwaterhavingaconductivitybelow10µS/cm(see9.4).Ontheotherhand,cleanandwell-platinizedelectrodesareincreas-inglyimportantintestingwaterofhigherconductivities,particularlyabove1000µS/cm.

9.2Thecellmanufacturer’sinstructionsmaybefollowedforcleaningtheelectrodesaswellasotherpartsofthecell.Asuitablecleaningsolutionconsistsofamixtureof1partbyvolumeofisopropylalcohol,1partofethylether,(withpolymercells,checkcompatibility)and1partofHCl(1+1).

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TABLE3ConductivityValuesofPureWaterandIncreasesDue

toSodiumChlorideA

Temperature,°C

05101520253035404550556065707580859095100

A

ConductivityofPureWater,ConductivityIncreaseDueto1

µS/cmmg/LNaCl,µS/cm

0.0116490.0166070.023100.031430.041940.055010.071010.090370.113510.140810.172680.20950.25140.29870.35160.41020.47440.54440.62050.70300.7930

1.14631.33111.52611.72971.94352.16422.39352.62962.87603.12573.38413.64763.91794.18824.47734.76485.05565.35505.65275.92646.1933

pick-upofcontaminantsfromtheairtothecontainingvesselduringtheseriesofmeasurements.

11.3In owingsystems,providemeansforvariableheatingorcoolingsothatthedesiredrangeoftemperaturewillbecovered.Regulatetherateof owthrougheachcellsoastokeepthecelladequately ushed.

11.4Fromthedataobtained,plotconductivityagainsttemperature.Makesurethattheconductivityreadingsareuncompensated.Fromthecurveatableoftemperaturecorrec-tionfactorsmaybeprepared,ortheratioofconductivityattemperatureTtoconductivityat25°CmaybeplottedagainsttemperatureT,andthisratioorcorrectionfactor,Q,takenfromthesmoothedcurve.

NOTE4—Dependingonthetypeofcompensationused,uncompensatedreadingsmaybeobtainedbysettingtemperatureto25°C,byputtingthetemperatureprobeina25°Cbath,orbysubstitutinganelectricalresistanceequivalentto25°C.

FromThornton(1)

.

11.5Whenusinganinstrumentprovidedwithamanualorautomatictemperaturecompensator,followthemanufacturer’sinstructionstocalibratethecompensatororcheckitsaccuracyandapplicabilitytothesamplebeingtested.

TESTMETHODA—FIELDANDROUTINE

LABORATORYMEASUREMENTOFSTATIC(NON-FLOWING)SAMPLES12.Scope

12.1Thistestmethodisapplicableto eldandroutinelaboratorymeasurementsoftheelectricalconductivityofwaterusingstaticsamples.

13.SummaryofTestMethod

13.1Thistestmethodutilizesdip-typeorpipet-typecon-ductivitycellsfortestingstaticsampleshavingconductivitiesgreaterthan10µS/cm.Temperaturecontrolandcorrectionmethodsarealsoprovided.

14.DeterminationofCellConstant

14.1Forthepurposesofthistestmethod,thecellconstantoftheconductivitycellusedshallbeknownwithin61%.Themanufacturer’scerti cationofthecellconstantwithinthisaccuracyisgenerallyconsideredsatisfactorybuttheuserisadvisedthatdamagecouldoccurinshipmentanditisbesttorecheckthecellconstantwhenreceived.Iftheconductivitycellhasbeeninserviceforaperiodsubsequenttothiscerti cation,itshallberecheckedbythemanufacturer,orinthelaboratory.

14.2Rinsetheconductivitycellseveraltimeswithwater,thenatleasttwicewiththeKClreferencesolutionthathasaconductivitynearesttothatofthesampleundertest(Table1).Controlthesolutiontemperatureto2560.1°C.Measuretheresistanceofthecell.RepeatthemeasurementonadditionalportionsoftheKClreferencesolutionuntilthevalueobtainedremainsconstanttowithinthelimitsofprecisioninaccordancewithSection18.

14.3Forinstrumentsreadingmeasuredresistanceinohms,calculatethecellconstant:

J51026·Rx~K11K2!

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comparinginstrumentreadingstakenwiththecellinquestionagainstreadingsonthesamesampleorseriesofsamplestakenwithaconductivitycellofknownorcerti edcellconstant.Exercisecaretoensurethatbothworkingandreferencecellsareatthesametemperatureor,alternatively,atdifferentbutknowntemperaturessothatacorrectionaslaterdescribedcanbeapplied.Resistivity-readinginstrumentswillindicateindirectproportiontothecellconstant,whileconductivityreadinginstrumentswillindicateininverseproportiontocellconstant.ConductivitycellsmaybecalibratedwithreferencesolutionsinaccordancewithSection14.

11.TemperatureCoefficientofConductivity/Resistivity11.1Theconductivity/resistivityofwaterandaqueousso-lutionsdependsstronglyuponthetemperature.(SeeTable3.)Thenormalpracticeistoreportconductivityandresistivityvaluesreferencedto25.0°C.Thecoefficientvariesdependinguponthenatureandcompositionofthedissolvedelectrolytes,andupontheconcentration.Thedissociationofwatercontrib-utessigni cantlytoconductivitiesat5µS/cmorlessandincreasesthetemperaturecoefficientfromnear2%per°Catabove5µS/cmtonear5%per°Cat0.055µS/cm.Toavoidmakingacorrection,itisnecessarytoholdthetemperatureofthesampleto2560.1°C.Ifthiscannotbedone,thetemperaturecoefficientmustbedeterminedandacorrectionapplied.Thisrequiresaseriesofconductivityandtemperaturemeasurementsonthesampleovertherequiredtemperaturerange.Whereautomatictemperaturecompensationisused,thetemperaturecompensationalgorithmshouldbechosenthatbestsimulatesthecompositionofthesamplestobetested.Inhighpuritywater,5µS/cmorless,thevariablecoefficientshallbeautomaticallydeterminedandappliedacrosstherangeofmeasurementforboththedissociationofwateranditsinter-actionwithsaltorothercontaminations.(SeeTestMethodD5391andRefs(10),(11),and(12)formoreinformation.)11.2Instaticsystems,exercisecaretoavoidchangeofcompositioncausedbylossofvolatileconstituentsorby

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14.4ForinstrumentsreadingmeasuredconductanceinSi-TABLE4PrecisionofTestMethodA

emens,calculatethecellconstant:

MeanConcentration,

OverallPrecision,St,

Single-OperatorPrecision

J51026·~KµS/cm

µS/cm

Pooled,So,µS/cm

11K2!/Kx

25.63.40.83NOTE5—Sincetheconductivitiesofamixtureoftwosolutionsarenot162.06.13.8exactlyadditive,theuseofK1+K2isonlyanapproximationandrequires1378.860.914.1thatK108169

6600

2918

2bemuchsmallerthanK1.

15.Procedure

15.1PrecisionMethodUsingTemperatureControl—Usea17.Report

dip-typeorpipet-typecell.Rinsethecell,container,and17.1Reportthevalueoftheconductivityat25°Cintermsofthermometerthoroughlyseveraltimeswithwaterandthentwomicrosiemenspercentimetretothenearest1%ofthedeter-ormoretimeswiththesample.Adjustthetemperatureto256minedconductivityifmeasurementsweremadeat2560.1°C,-

--0.1°Casindicatedbyathermometerasdescribedin6.3.1.otherwisereporttothenearest3%ofthedeterminedconduc-`,,`,`,Allowsufficienttimeforequalizationoftemperatures.Readtivity.

,`,,`-theconductanceorresistance.Calculateconductivityorresis-17.2Alternatively,reportthevalueoftheresistivityat25°C`-````tivityaccordingtoSection16usingQ=1,sincenotempera-intermsofohm-centimetrestothenearest1%ofthedeter-,,,turecorrectionisrequired.

minedresistivityifmeasurementsweremadeat2560.1°C,,```,,15.2RoutineMethodUsingTemperatureCorrection—Useotherwisereporttothenearest3%ofthedeterminedresistiv-`--adip-typeorpipet-typecell.Rinsetheconductivitycellity.

thoroughlyseveraltimeswithwaterandthentwoormore18.PrecisionandBias6

timeswiththesample.Measuretheresistanceortheconduc-tance,andthetemperature(tothenearest0.1°C),onsuccessive18.1Thistestmethodwastestedbyninelaboratories,atportionsofthesampleuntilaconstantvalueisobtained.Ifthefourconcentrationlevels,witheachoperatoranalyzingeachmeasuringinstrumentisprovidedwithamanualtemperaturesampleonthreedifferentdays.Thesecollaborativetestdatacompensator,adjustthistothesampletemperaturevaluewereobtainedonreagentwater.Forothermatrices,thesedatabeforereadingtheinstrument.Ifanautomatictemperaturemaynotapply.Thesedataweredevelopedusingtheroutinecompensatorisprovided,noadjustmentisnecessary,butmethod(temperaturecorrection)describedin15.2.Theactualsufficienttimemustbeallowedtopermitequalizationoftemperatureofsamplestestedbytheparticipantsrangedfromtemperature.Iftheinstrumenthasnomeansoftemperature18.5to26.0°C.

compensation,determineatemperaturecorrectionfactorin18.1.1Precision—TheprecisionofthistestmethodwithinaccordancewiththeinstructionsinSection11toconvertitsdesignatedrangeappearsinTable4.

readingsto25°C.Ifinstrumenttemperaturecompensationis18.1.2Bias—Recoveriesofknownamountsofconductivityused,calculateconductivityorresistivityaccordingtoSectionvaluesinaseriesofpreparedstandardsappearsinTable5.16usingQ=1,otherwiseuseQasdeterminedinSection11.18.2Thistestmethodmeetsrequirementsforprecisionandbiasspeci edinPracticeD2777–86.

16.Calculation

TESTMETHODB—CONTINUOUS,IN-LINE

16.1Forinstrumentsreadingmeasuredresistanceinohms,MEASUREMENTcalculatetheconductivityofthesample:

19.Scope

K5106·J/RxQ

19.1Thistestmethodisapplicabletothecontinuous,in-line16.2Forinstrumentsreadingmeasuredresistanceinohms,measurementoftheelectricalconductivityofwater.calculatetheresistivityofthesample:

20.SummaryofTestMethod

R5RxQ/J

20.1Thistestmethodutilizesa ow-typeconductivitycell16.3ForinstrumentsreadingmeasuredconductanceinSi-tosampleacontinuousstreamofthewaterundertest.emens,calculatetheconductivityofthesample:

Temperaturecontrolandcorrectionmethodsarealsoprovided.K5106·JKx/Q

21.Procedure

16.4ForinstrumentsreadingmeasuredconductanceinSi-emens,calculatetheresistivityofthesample:

21.1PrecisionMethodUsingTemperatureControl—Usea ow-typeconductivitycell.Adjustthesamplestream,knownR5Q/JKx

tobefreeofcorrosionproductsandotherparticulatecontami-16.5Automaticrecordersandindicatorsprovidedwithtem-nation,toaproper owrateandbringthetemperatureto256peraturecompensators,whenusedwithconductivitycellsof0.1°Casindicatedbyathermometerasdescribedin6.3.Allowtherequiredcellconstant,usuallyreaddirectlyintermsofsufficienttimetoreachequalizationoftemperatures.Readthe

siemenspercentimetreorµS/cmreferredto25°C.Nocalcu-lationsarenecessaryifthecompensatoriscorrectedforthe6

solutioninthecell.

Supportingdatahavebeen ledatASTMInternationalHeadquartersandmaybeobtainedbyrequestingResearchReportRR:D19–1139.

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Provided by IHS under license with ASTM

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TABLE5BiasofTestMethodA

AmountsAdded,µS/cm27.8167.61408.8111342

Mean

Recovery,x,µS/cm25.6162.01378.8108169

Bias 2.2 5.6 30.0 3173

%Bias 7.9 3.3 2.1 2.8

StatisticallySigni cant

yesyesyesyes

22.Report

22.1Reportthevalueoftheconductivityat25°Cintermsofmicrosiemenspercentimetretothenearest1%ofthedeter-minedconductivityifmeasurementsweremadeat2560.1°C,otherwisereporttothenearest3%ofthedeterminedconduc-tivity.

22.2Alternatively,reportthevalueoftheresistivityat25°Cintermsofohm-centimetrestothenearest1%ofthedeter-minedresistivityifmeasurementsweremadeat2560.1°C,otherwisereporttothenearest3%ofthedeterminedresistiv-ity.

23.PrecisionandBias

23.1Sincethistestmethodinvolvescontinuoussampling,ageneralstatementofprecisionandbiasisnotapplicable.23.2Experiencehasshownthaterrorsof1to30%maybeencountered,dependingontheequipmentandtechniquesused.Errorsintemperaturecompensationareespeciallytroublesomeatconductivitiesbelow10µS/cm.Additionalerrorsmaybeencounteredwithlowconstantcellsbecauseofthedifficultiesinvolvedinverifyingthecellconstantatlowconductivitylevels.24.Keywords

24.1cellconstant;conductivity;resistivity;temperaturecoefficient

conductanceorresistance.Calculatetheconductivityorresis-tivityaccordingtoSection16usingQ=1,sincenotempera-turecorrectionisrequired.

21.2RoutineMethodUsingTemperatureCorrection—Usea ow-typeconductivitycell.Adjustthesamplestream,knowntobefreeofcorrosionproductsandotherparticulatecontami-nation,toaproper owrateandbringthetemperaturetoasteadyvalueasnear25°Caspossible.Readthetemperaturetothenearest0.1°C.Ifthemeasuringinstrumentisprovidedwithamanualtemperaturecompensator,adjustthistothesampletemperaturevalue.Ifanautomatictemperaturecompensatorisprovided,noadjustmentisnecessarybutsufficienttimemustbeallowedtopermitequalizationoftemperatures.Readtheconductanceorresistance.Iftheinstrumenthasnomeansoftemperaturecompensation,determineatemperaturecorrectionfactorinaccordancewithSection11toconvertreadingsto25°C.Ifinstrumenttemperaturecompensationisused,calcu-lateconductivityorresistivityaccordingtoSection16usingQ=1,otherwiseuseQasdeterminedinSection11.

REFERENCES

(1)Thornton,R.D.,Light,T.S.,“ANewApproachtoAccurateResis-tivityMeasurementofHighPurityWater,”UltrapureWater,Vol6,No.5,1989,pp.14–26.

(2)SymposiumonPowerPlantInstrumentationforMeasurementofHigh-PurityWaterQuality,ASTMSTP742,ASTM,1981.

(3)“MethodsforDeterminationofQualityandPurityofSteam,”ASMEPowerTestCode,SupplementonInstrumentsandApparatus,Part19.11.

(4)Rossum,J.R.,“ConductanceMethodforCheckingAccuracyofWaterAnalyses,”AnalyticalChemistry,Vol21,1949,p.631.

(5)Jones,G.,Bradshaw,B.C.,“TheMeasurementoftheConductanceofElectrolytes,V.A.RedeterminationoftheConductanceofStandardKClSolutionsinAbsoluteUnits,”JournalofAmericanChemicalSociety,Vol55,1933,p.1780.

(6)Wu,Y.C.,Koch,W.F.,Hamer,W.J.,Kay,R.L.,“ReviewofElectrolyticConductanceStandards,”JournalofSolutionChemistry,Vol16,No.12,1987,pp.985–997.

(7)Wu,Y.C.,Pratt,K.W.,Koch,K.F.,“DeterminationoftheAbsolute

Speci cConductanceofPrimaryStandardKClSolutions,”JournalofSolutionChemistry,Vol18,No.6,1989,pp.515–528.

(8)Shedlovsky,T.,“TheElectrolyticConductivityofSomeUnivalentElectrolytesinWaterat25°C,”JournalofAmericanChemicalSociety,Vol54,1932,p.1411.

(9)InternationalCriticalTables,Vol3,1928,p.87.

(10)Light,T.S.,Licht,L.L.“ConductivityandResistivityofWaterfrom

theMeltingtoCriticalPoints,”AnalyticalChemistry,Vol59,1987,pp.2327–2330.

(11)Harned,H.S.,Owen,B.B.,ThePhysicalChemistryofElectrolytic

Solutions,ThirdEd.,ReinholdPublishingCorp.,NewYork,1958,p.234.

(12)Gray,D.M.,Tenney,A.S.,“ImprovedConductivity/ResistivityTem-peratureCompensationforHighPurityWater,”UltrapureWater,July/August,1986.

(13)Glasstone,S.,AnIntroductiontoElectrochemistry,D.VanNos-trand,NewYork,1942,pp.50,56,61.

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