Designation:D7638−10(Reapproved2015)StandardTestMethodforDeterminationofFattyAcidsandEstersinGlycerin1ThisstandardisissuedunderthefixeddesignationD7638;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.1.Scope1.1Thistestmethodprovidesthequantitativedeterminationofthefattyacidandestercontentinpurifiedglycerinbythetitrimetricmethod.1.2ThevaluesstatedinSIunitsaretoberegardedasstandard.Nootherunitsofmeasurementareincludedinthisstandard.1.3Thisstandardmayinvolvehazardousmaterials,opera-tionsandequipment.Thisstandarddoesnotpurporttoaddressallofthesafetyconcerns,ifany,associatedwithitsuse.Itistheresponsibilityoftheuserofthisstandardtoestablishappropriatesafetyandhealthpracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.SpecificprecautionsarelistedinSection8.2.ReferencedDocuments2.1ASTMStandards:2D1193SpecificationforReagentWaterD4725TerminologyforEngineCoolantsandRelatedFluids2.2OtherStandard:TheUnitedStatesPharmacopoeia31GlycerinMonograph–FattyAcidsandEsters33.Terminology3.1Definitions:3.1.1glycerin—propane-1,2,3-Triol,C3H5(OH)3(alsoknownasglycerine),1,2,3-propanetriol,1,2,3-trihydroxypropane,glyceritol,glycylalcohol.CAS#56-81-53.1.2FA&E—FattyacidandEsters3.1.3Forotherdefinitionsoftermsusedinthisspecification,refertoTerminologyD4725.4.SignificanceandUse4.1Anyresidualfattyacidandesters(FA&E)shouldbepresentonlyatverylowlevelsinpurifiedglycerine.4.2Thisprocedurerequirestheadditionofameasuredvolumeofsodiumhydroxide,inexcessoftheamountactuallyneededtoreactwithFA&Eintheglycerinesample.Afterboiling,theexcesssodiumhydroxideisbacktitratedwithstandardizedhydrochloricacid.Thequantityofthesubstancebeingtitratediscalculatedasthedifferencebetweenthevolumesofthesodiumhydroxidesolutionoriginallyadded,correctedbymeansofablanktitration,andthatwasconsumedbytheti...
