Designation:D6739−11(Reapproved2015)StandardTestMethodforSilica—pHValue1ThisstandardisissuedunderthefixeddesignationD6739;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1ThistestmethodisusedtomeasurethepHofa5%silica/watersuspensionormechanicaldispersionandisindica-tiveoftherelativeacidityoralkalinityofthesilica.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2E70TestMethodforpHofAqueousSolutionsWiththeGlassElectrodeE177PracticeforUseoftheTermsPrecisionandBiasinASTMTestMethodsE691PracticeforConductinganInterlaboratoryStudytoDeterminethePrecisionofaTestMethod3.SignificanceandUse3.1ThepHlevelofsilica,asmeasuredbythistestmethod,isknowntoaffectthevulcanizationofsomerubbercom-pounds.RefertoTestMethodE70forafullerunderstandingofpHandamoredetailedprocedureformakingpHmeasure-ments.4.Apparatus4.1pHMeter,(digitalisrecommended),havinganaccuracyof60.05pHandequippedwithacombinationelectrode.4.2MortarandPestle.4.3Beaker,glass,150cm3withwatchglass.4.4MagneticStirringBarandStirrer.5.Reagents5.1Degassed,NeutralWater.Boilacontainerofeitherdistilledordeionizedwaterfor10min,cover,andallowtocooltoroomtemperature,orpurgethewaterwithnitrogengasfor20minusingafrittedbubbler.5.2BufferSolutions,pHof4.00,7.00,and10.00.6.Procedure6.1Pulverizepelletedorgranulatedsilicatoafinepowder,usingamortarandpestle.6.2Weigh5gofsilicatothenearest0.1gintoa150cm3glassbeaker.6.3Add100cm3ofdegassed,neutralwater.6.4Covertheglassbeakerwithawatchglassandstirthemixtur...
