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1、METHOD9035SULFATE(COLORIMETRIC,AUTOMATED,CHLORANILATE)1.0SCOPEANDAPPLICATION1.1Thisautomatedmethodisapplicabletogroundwater,drinkingandsurfacewaters,anddomesticandindustrialwastescontaining10to400mg-2SO4/liter.2.0SUMMARYOFMETHOD2.1Whensolidbariumchloranilat
2、eisaddedtoasolutioncontainingsulfate,bariumsulfateisprecipitated,releasingthehighlycoloredacidchloranilateion.Thecolorintensityintheresultingchloranilicacidsolutionisproportionaltotheamountofsulfatepresent.3.0INTERFERENCES3.1Cationssuchascalcium,aluminum,an
3、dironinterferebyprecipitatingthechloranilate.Theseionsareremovedbypassagethroughanion-exchangecolumn.3.2Samplesshouldbecentrifugedorfilteredbeforeanalysis.4.0APPARATUSANDMATERIALS4.1Automatedcontinuous-flowanalyticalinstrument,with:4.1.1SamplerI.4.1.2Contin
4、uousfilter.4.1.3Manifold.4.1.4Proportioningpump.4.1.5Colorimeter:Equippedwith15mmtubularflowcelland520nmfilters.4.1.6Recorder.4.1.7Heatingbath,45EC.4.2Magneticstirrer.90351CD-ROMRevision0DateSeptember19865.0REAGENTS5.1ASTMTypeIIwater(ASTMD1193):Watershouldb
5、emonitoredforimpurities.5.2Bariumchloranilate:Add9gofbariumchloranilate(BaC6Cl2O4)to333mLofspectrophotometricgradeethylalcoholanddiluteto1literwithTypeIIwater.5.3Acetatebuffer,pH4.63:Dissolve13.6gofsodiumacetateinTypeIIwater.Add6.4mLofaceticacidanddiluteto1
6、literwithTypeIIwater.Makefreshweekly.5.4NaOH-EDTAsolution:Dissolve65gofNaOHand6gEDTAinTypeIIwateranddiluteto1liter.Thissolutionisalsousedtocleanoutthemanifoldsystematendofsamplingrun.+5.5Ionexchangeresin:Dowex-50W-X8,ionicform-H.Thecolumnispreparedbysucking
7、aslurryoftheresininto12in.of3/16-inO.D.tubing.Thismaybeconvenientlydonebyusingapipetandaloose-fittingglasswoolpluginthetube.Thecolumn,uponexhaustion,turnsred.Ensurethatairdoesnotenterthecolumn.5.6Stocksolution:Dissolve1.4790gofoven-dried(105EC)Na2SO4inTypeI
8、Iwateranddiluteto1literinavolumetricflask(1.0mL=1.0mg).5.7Standards:Prepareaseriesofstandardsbydilutingsuitablevolumesofstocksolutionto100.0mLwithTypeIIwater.Thefollowingdilutionsaresuggested.StockSolu
