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1、AppendixA:StandardSolutionsandReferenceMaterialsA.1.01at105EC,andstoreinbrownglass-stopperedbottleindarkoverAOACOfficialMethod942.25gooddesiccant.StandardSolutionsandMaterials(b)Referencesolution.—Tomixtureof5mLHNO3(1+1),2mLFirstAction1942ferricalumsolution,941.18D(a)(seeA.
2、1.11),and115mLH2O,addca0.02mL0.1Mthiocyanate,B,notingexactvolumeused.Useaccuratelycalibratedequipment,whichmeetsNISTspecifi-B.PreparationofStandardSolutioncations.Alkalineandothercorrosivesolutionsdissolveglass.Toavoidvolumetricerrors,donotstoresuchsolutionsincalibratedap-P
3、repareca0.1Msolutionfromreagentthatshowsnochlorineus-paratus.Buretsusedcontinuouslywithsuchsolutionsshouldbeing7.612gNH4SCNor9.718gKSCN/L.recalibratedperiodically.C.StandardizationWorkingtemperatureofstandardsolutionshouldapproximatethatofitstemperatureduringstandardization
4、.Iftemperaturecorrec-Accuratelyweigh,ontaredwatchglass,enoughpurifiedAgNO3togivetitrationofca40mL(ca0.7gfor0.1Msolution)andtransferwithtionsarenecessary,sufficientaccuracymaybeobtainedbyuseofTable942.25.H2Othroughglassfunnelto250mLglass-stopperedErlenmeyer.Dissolveinca75mLH
5、2O(halogen-free),andadd5mLHNO3(1+1)Reference:JAOAC25,650(1942).and2mLferricalumsolution,941.18D(a)(seeA.1.11).TitratewiththiocyanatesolutionuntiltitratedsolutionachievesareddishbrownA.1.02color,whichremainsaftershakingvigorously1min.Recordburetreadingandsetflaskaside5min,sh
6、akingoccasionallyandmaintain-AOACOfficialMethod942.26ingendpointcolorbyadditionofthiocyanatesolutionasrequired.StandardSolutionsThenaddadditionalthiocyanatesolution,ifnecessary,toproduceofAmmoniumandPotassiumThiocyanatespermanentendpointcolor,matchingwithcolorofreferencesol
7、ution,FirstAction1942FinalActionA(b).Fromtotalvolumethiocyanatesolutionusedintitration,sub-tractvolumecontainedinreferencesolution.A.Reagents(a)Purifiedsilvernitrate.—Dissolve50gAgNO3in20mLboil-Molarity(mol/L)=gAgNO3×1000/mLtiter×169.87ingH2Ocontainingca5dropsNHO3.Heattodis
8、solve,filterwhilestillhotthroughfrittedglassfilter,usingsuction,andcollectfiltrate
