EPA 9253 CHLORIDE (TITRIMETRIC, SILVER NITRATE)

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1、METHOD9253CHLORIDE(TITRIMETRIC,SILVERNITRATE)1.0SCOPEANDAPPLICATION1.1Thismethodisintendedprimarilyforoxygenbombcombustatesorotherwaterswherethechloridecontentis5mg/LormoreandwhereinterferencessuchascolororhighconcentrationsofheavymetalionsrenderMethod9252impracticable.2.0SUMM

2、ARYOFMETHOD2.1WateradjustedtopH8.3istitratedwithsilvernitratesolutioninthepresenceofpotassiumchromateindicator.Theendpointisindicatedbypersistenceoftheorange-silverchromatecolor.3.0INTERFERENCES3.1Bromide,iodide,andsulfidearetitratedalongwiththechloride.Orthophosphateandpolyph

3、osphateinterfereifpresentinconcentrationsgreaterthan250and25mg/L,respectively.Sulfiteandobjectionablecolororturbiditymustbeeliminated.CompoundsthatprecipitateatpH8.3(certainhydroxides)maycauseerrorbyocclusion.3.2Residualsodiumcarbonatefromthebombcombustionmayreactwithsilvernit

4、ratetoproducetheprecipitate,silvercarbonate.Thiscompetitivereactionmayinterferewiththevisualdetectionoftheendpoint.Toremovecarbonatefromthetestsolution,addsmallquantitiesofsulfuricacidfollowedbyagitation.4.0APPARATUSANDMATERIALS4.1Standardlaboratorytitrimetricequipment,includi

5、ng1mLor5mLmicroburetwith0.01mLgradations,and25mLburet.4.2Analyticalbalance:capableofweighingto0.0001g.4.3ClassAvolumetricflask:1L.5.0REAGENTS5.1Reagentgradechemicalsshallbeusedinalltests.Unlessotherwiseindicated,itisintendedthatallreagentsshallconformtothespecificationsoftheCo

6、mmitteeonAnalyticalReagentsoftheAmericanChemicalSociety,wheresuchspecificationsareavailable.Othergradesmaybeused,provideditisfirstascertainedthatthereagentisofsufficientlyhighpuritytopermititsusewithoutlesseningtheaccuracyofthedetermination.5.2Reagentwater.Allreferencestowater

7、inthismethodrefertoreagentwater,asdefinedinChapterOne.5.3Hydrogenperoxide(30%),H202.CD-ROM9253-1Revision0September19945.4Phenolphthaleinindicatorsolution(10g/L).5.5Potassiumchromateindicatorsolution.Dissolve50gofpotassiumchromate(K2Cr04)in100mLofreagentwaterandaddsilvernitrate

8、(AgN03)untilaslightlyredprecipitateisproduced.Allowthesolutio