EPA METHOD 9034 Titrimetric Procedure for Acid-Soluble and

《EPA METHOD 9034 Titrimetric Procedure for Acid-Soluble and》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、METHOD9034TITRIMETRICPROCEDUREFORACID-SOLUBLEANDACIDINSOLUBLESULFIDES1.0SCOPEANDAPPLICATION1.1Thisproceduremaybeusedasadeterminativestepforacid-solubleandacid-insolublesulfidesfollowingdistillationofthesamplebySW-846Method9030.1.2Method9034issuitablefor

2、measuringsulfideconcentrationsinsampleswhichcontain0.2mg/kgto50mg/kgofsulfide.2.0SUMMARYOFMETHODSulfideisextractedfromthesamplebyapreliminarydistillationprocedure(SeeMethod9030)andprecipitatedinanzincacetatescrubberaszincsulfide.Thesulfideisoxidizedtosu

3、lfurbyaddingaknownexcessamountofiodine.Theexcessiodineisdeterminedbytitrationwithastandardsolutionofphenylarsineoxide(PAO)orsodiumthiosulfateuntiltheblueiodinestarchcomplexdisappears.Astheuseofstandardsulfidesolutionsisnotpossiblebecauseofoxidativedegra

4、dation,quantitationisbasedonthePAOorsodiumthiosulfate.3.0INTERFERENCES3.1Theiodometricmethodsuffersinterferencefromreducingsubstancesthatreactwithiodine,includingthiosulfate,sulfite,andvariousorganiccompounds.3.2RefertoMethod9030foradiscussionofothersul

5、fideinterferences.4.0APPARATUSANDMATERIALS4.1500mLflasks.4.2Hotplatestirrer.4.325mLburet.4.4Volumetricpipets.5.0REAGENTS5.1Reagentgradechemicalsshallbeusedinalltests.Unlessotherwiseindicated,itisintendedthatallreagentsshallconformtothespecificationsofth

6、eCommitteeonAnalyticalReagentsoftheAmericanChemicalSociety,wheresuchspecificationsareavailable.Othergradesmaybeused,provideditisfirstascertainedthatthereagentisofsufficientlyhighpuritytopermititsusewithoutlesseningtheaccuracyofthedetermination.5.2Reagen

7、twater.Allreferencestowaterinthismethodrefertoreagentwater,asdefinedinChapterOne.CD-ROM9034-1Revision0December19965.3Starchsolution-Useeitheranaqueoussolutionorsolublestarchpowdermixtures.Prepareanaqueoussolutionasfollows.Dissolve2gsolublestarchand2gsal

8、icylicacid,C7H6O3,asapreservative,in100mLhotreagentwater.5.4Iodinesolution(approximately0.025N)5.5Dissolve25gpotassiumiodide,KI,in700mLofreagentwaterina1-litervolumetricflask.Add3.2giodine,I2.Allowtodissolve.Addthetypeandamountof