Designation:D3898−93(Reapproved2015)StandardTestMethodforChromicOxideinBasicChromiumTanningLiquors1ThisstandardisissuedunderthefixeddesignationD3898;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodcoversthedeterminationofchromicoxideinchrometanningliquors,eithersimple,withaddedaluminumorzirconium,orwiththeusualmaskingcomplexingagents.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D2807TestMethodforChromicOxideinLeather(Perchlo-ricAcidOxidation)3.SummaryofTestMethod3.1Thesolutionisoxidizedwithsodiumperoxideuntilthechromiumiscompletelyconvertedtothechromateion.Thesolutionisboiledtocompleteoxidationoforganicmaterialsandtodestroyexcessperoxide;itisthencooledandacidified.Potassiumiodideisaddedandtheliberatediodineistitratedwithstandardizedsodiumthiosulfate.4.SignificanceandUse4.1Theproceduredescribedisforthequalitycontrolformanufacturingliquorsandspecificationsforthepurchaseofsuchliquors.4.2Thechromiumcontentoftheliquorsdeterminestheamounttobeusedtoobtainthedesireddegreeoftannage,andhencemaybeamatterforspecificationinthepurchaseofleather.5.Interferences5.1Thetestmethodisgenerallythemostaccurateandconvenientforthepurpose.However,iftheliquorcontainsironorcopper,whichinterferewiththesodiumthiosulfatetitration,orcomplexorganicorinorganicreducingagents(sodiumthiosulfate,forexample)whicharenotoxidizedbyalkalineperoxidebutreducehexavalentchromiumonacidification,analternateproceduremustbeused.Theper-chloricacidmeth...
