Designation:D2868−10(Reapproved2015)StandardTestMethodforNitrogenContent(Kjeldahl)andHideSubstanceContentofLeather,WetBlueandWetWhite1ThisstandardisissuedunderthefixeddesignationD2868;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheU.S.DepartmentofDefense.1.Scope1.1Thistestmethodcoversthedeterminationofthenitro-gencontentofalltypesofleather,wetblueandwetwhite.Thenitrogencontentisusedtocalculatethehidesubstance(proteinfiber)contentofleather,wetblueandwetwhite.NOTE1—TheoriginaltestmethodforleatherwasessentiallyacompositeofMethod6441ofFederalTestMethodStandardNo.311andMethodB5oftheAmericanLeatherChemistsAssociation.NOTE2—Melamine,ifpresentinbondedleather,couldgiveanartificiallyhighvalueforthecalculationofproteinfiber.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappro-priatesafetyandhealthpracticesanddeterminetheapplica-bilityofregulatorylimitationspriortouse.2.ReferencedDocuments2.1ASTMStandards:2D2813PracticeforSamplingLeatherforPhysicalandChemicalTestsD6659PracticeforSamplingandPreparationofWetBlueforPhysicalandChemicalTestsE177PracticeforUseoftheTermsPrecisionandBiasinASTMTestMethodsE691PracticeforConductinganInterlaboratoryStudytoDeterminethePrecisionofaTestMethod3.SummaryofTestMethod3.1Thespecimenpreparedaccordingtoanacceptedproce-dure(seeNote3)isdigestedwithacidinthepresenceofacatalysttoconvertthenitrogentoammoniumion.Theammo-niumionformedisnonvolatileunderthesehighlyacidconditions.NOTE3—ForleatherusespecimenpreparedperPracticeD2813.Forwetblueandwetwhite,usespecimenpreparedperPracticeD6659.3.2Theacidmixtur...
