102-Melting Point Melting Range

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1、102Adopted:27.07.95OECDGUIDELINEFORTHETESTINGOFCHEMICALSthAdoptedbytheCouncilon27July1995MeltingPoint/MeltingRangeINTRODUCTION1.ThisguidelineisarevisedversionoftheoriginalGuideline102whichwasadoptedin1981.Mainlytheformathasbeenchanged.Thedifferencesofsubstancebetween

2、thisversionandthatfrom1981arefew.Themeniscusmethod,whichisapplicabletopolyamides,hasnotbeenretainedandthepourpointisincluded.TherevisionwasbasedontheECmethod"Melting/FreezingTemperature"publishedin1992(1).INITIALCONSIDERATIONS2.Frequentlythetransitionfromsolidtoliqui

3、dphasetakesplaceoveratemperaturerange.Therefore,theterm"meltingrange"isoftenusedand,inpractice,thetemperaturesoftheinitialandfinalstagesofmeltingaredetermined.Themeltingpointideallyisidenticalwiththesolidificationorfreezingpoint.Forsomesubstances(ratherproductsandmix

4、tures)however,thedeterminationofthefreezingorsolidificationtemperatureiseasier.Where,duetotheparticularpropertiesofthesubstance(orproduct),noneoftheaboveparameterscanbeconvenientlymeasured,apourpointmaybeappropriate.3.Thefundamentalprinciplesaregiveninreferences2and3

5、.Severalmethodsanddevicesaredescribedinthisguideline.Theycanbeappliedirrespectiveofthedegreeofpurityofthesubstance.Themeltingpointofasubstanceisconsiderablyaffectedbyimpurities.Forthisreasonitservesasameasureofasubstance'spurity.Theselectionofaparticularmethoddepends

6、mainlyonthestateofphysicalaggregationofthesampleandonwhetherornotthesubstancecanbepulverizedeasily,withdifficulty,ornotatall.StandardsdescribingthevariousdevicesandproceduresarelistedintheAppendix.DEFINITIONSANDUNITS4.Themeltingpointisdefinedasthetemperatureatwhichth

7、ephasetransitionfromthesolidtotheliquidstateatatmosphericpressuretakesplace.5.TheconversionofkelvinstodegreesCelsiusisaccordingtotheformulaT=t+273.15,whereTistheKelvinorthermodynamictemperatureandttheCelsiustemperature.1/8102OCDE/OECDREFERENCESUBSTANCES6.Referencesub

8、stancesdonotneedtobeemployedwheninvestigatingasubstance.Somecalibrationsubstancesarelistedinreference4.PRINCIPLEOFTHETEST7.Thetempe