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【英文标准名称】:StandardTestMethodforpHMeasurementofWaterofLowConductivity
【原文标准名称】:低传导率水pH值测量的标准试验方法
【标准号】:ASTMD5464-2007
【标准状态】:现行
【国别】:
【发布日期】:2007
【实施或试行日期】:
【发布单位】:美国材料与试验协会(US-ASTM)
【起草单位】:D19.03
【标准类型】:(TestMethod)
【标准水平】:()
【中文主题词】:酸度;强碱性;高;检验;低;pH值;试验;水;水处理
【英文主题词】:automatictemperaturecompensator;controlledleakagerate;flowingliquidjunction;highpuritywater;liquidjunctionpotential;lowconductivitywater;pHglasselectrode;pHtemperaturecoefficient;referenceelectrode;solutiontemperaturecoef
【摘要】:pHmeasurementoflowconductivitywaterisfrequentlyappliedtopowerplantwaterandcondensedsteamsamplesforcorrosionandscaleprevention.Itissometimesusedinpurewatertreatmentsystemsbetweenmultiplepassmembranestooptimizeperformance.HighpuritywaterishighlyunbufferedandsmallamountsofcontaminationcanchangethepHsignificantly.Specifically,highpuritywaterrapidlyabsorbsCO2gasfromtheatmosphere,whichlowersthepHofthesample.ThesamplecontainerandaccompanyingpHmeasurementtechniqueminimizeexposureofthehighpuritywatersampletotheatmosphere.Thehighpuritywatersamplemaycontainvolatiletracecomponentsthatwilldissipatefromthesampleifexposedtotheatmosphere.Thesamplecontainerusedinthistestmethodwillpreventtheselosses.Highpuritywaterhasasignificantsolutiontemperaturecoefficient.Forgreatestaccuracythesampletobemeasuredshouldbeclosetothetemperatureofthesamplestreamandappropriatecompensationshouldbeapplied.WhenthepreferredTestMethodD5128,whichrequiresareal-time,flowingsample,cannotbeutilizedforpracticalreasonssuchasphysicalplantlayout,unacceptablelossofwater,locationofon-lineequipmentsamplepoints,oravailabilityofdedicatedtestequipment,thismethodoffersaviablealternative.ThemostsignificantdifferencebetweenthetwotestmethodsisthatTestMethodD5128obtainsareal-timepHmeasurementfromaflowingsampleandthismethodobtainsatimedelayedpHmeasurementfromastaticgrabsample.pHmeasurementsoflowconductivitywaterarealwayssubjecttointerferences(7.1-7.5)andTestMethodD5128ismoreeffectiveineliminatingtheseinterferencesespeciallywithregardtocontamination.Thisstaticgrabsamplemethodismorepronetocontaminationandtemperature-inducederrorsbecauseofthetimelagbetweenthesamplingintheplantandsamplepHreadingwhichistakeninthelaboratory.1.1ThistestmethodisapplicabletodeterminethepHofwatersampleswithaconductivityof2to100181S/cmoverthepHrangeof3to11.pHmeasurementsofwateroflowconductivityareproblematic.Specifically,thistestmethodavoidscontaminationofthesamplewithatmosphericgasesandpreventsvolatilecomponentsofthesamplefromescaping.ThistestmethodprovidesforpHelectrodesandapparatusthataddressadditionalconsiderationsdiscussedin.Thistestmethodalsominimizesproblemsassociatedwiththesample''spHtemperaturecoefficientwhentheoperatorusesthistestmethodtocalibrateanon-linepHmonitororcontroller(seeAppendixX1).1.2ThistestmethodcoversthemeasurementofpHinwateroflowconductivitywithalowerlimitof2.0181S/cm,utilizingastaticgrab-sampleprocedurewhereitisnotpracticabletotakeareal-timeflowingsample.Note1TestMethodD5128foron-linemeasurementispreferredoverthismethodwheneverpossible.TestMethodD5128isnotsubjecttothelimitedconductivityrange,temperatureinterferences,potentialKClcontamination,andtimelimitationsfoundwiththismethod.1.3Foron-linemeasurementsinwaterwithconductivityof100181S/cmandhigher,seeTestMethodD6569.1.4Forlaboratorymeasurementsinwaterwithconductivityof100181S/cmandhigher,seeTestMethodD1193.1.5ThevaluesstatedinSIunitsaretoberegardedasstandard.Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.
【中国标准分类号】:Z12
【国际标准分类号】:13_060_50
【页数】:10P.;A4
【正文语种】: