Designation:D2879−10StandardTestMethodforVaporPressure-TemperatureRelationshipandInitialDecompositionTemperatureofLiquidsbyIsoteniscope1ThisstandardisissuedunderthefixeddesignationD2879;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginaladoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscriptepsilon(´)indicatesaneditorialchangesincethelastrevisionorreapproval.ThisstandardhasbeenapprovedforusebyagenciesoftheDepartmentofDefense.1.Scope1.1Thistestmethodcoversthedeterminationofthevaporpressureofpureliquids,thevaporpressureexertedbymixturesinaclosedvesselat4065%ullage,andtheinitialthermaldecompositiontemperatureofpureandmixedliquids.Itisapplicabletoliquidsthatarecompatiblewithborosilicateglassandthathaveavaporpressurebetween133Pa(1.0torr)and101.3kPa(760torr)attheselectedtesttemperatures.Thetestmethodissuitableforuseovertherangefromambientto748K.Thetemperaturerangemaybeextendedtoincludetem-peraturesbelowambientprovidedasuitableconstant-temperaturebathforsuchtemperaturesisused.NOTE1—Theisoteniscopeisaconstant-volumeapparatusandresultsobtainedwithitonotherthanpureliquidsdifferfromthoseobtainedinaconstant-pressuredistillation.1.2Mostpetroleumproductsboiloverafairlywidetem-peraturerange,andthisfactshallberecognizedindiscussionoftheirvaporpressures.EvenanidealmixturefollowingRaoult’slawwillshowaprogressivedecreaseinvaporpressureasthelightercomponentisremoved,andthisisvastlyaccentuatedincomplexmixturessuchaslubricatingoilscontainingtracesofdewaxingsolvents,etc.Suchamixturemaywellexertapressureinaclosedvesselofasmuchas100timesthatcalculatedfromitsaveragecomposition,anditistheclosedvesselwhichissimulatedbytheisoteniscope.Formeasurementoftheapparentvaporpressureinopensystems,TestMethodD2878,isrecommended.1.3ThevaluesstatedinSIunitsaretoberegardedasthestandard.Thevaluesinparenthesesareforinformationonly.1.4WARNING—Mercuryhasbeendesignatedbymanyregulatoryagenciesasahazardousmaterialthatcancausece...
