Asbestos RI Measurment用色散染色法测定石棉折射率的标准操作规程英文.docx
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Asbestos RI Measurment用色散染色法测定石棉折射率的标准操作规程英文.docx
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AsbestosRIMeasurment用色散染色法测定石棉折射率的标准操作规程英文
RapidlyAndAccuratelyDetermining
RefractiveIndicesOfAsbestosFibers
ByUsing
DispersionStainingMethod
AStandardOperationProcedureFor
BulkAsbestosAnalysisBy
PolarizedLightMicroscopy
Shu-ChunSu,Ph.D.
Rev.2010-07-11
Forthoselaboratoriesthathavereceivedearlierversionsofthispaper,pleasereplacethemwiththisupdatedversion.Amuchcondensedversionofthispaperwaspublishedin2003:
Arapidandaccurateprocedureforthedeterminationofrefractiveindicesofasbestosminerals.AmericanMineralogist,88,1979-1982.
Ifanyonehasanyquestionsorsuggestionsconcerningthisprocedureorneedtheelectronicfiles(WordorPDFformat),pleasecontactmeatshuchunsu@.
Thisversionhascorrectedanerrorwiththetwocrocidolitetables(Tables7and8):
αandγtablesweretransposedinolderversionsalthoughtheresultantdifferencesbetweentheRIsobtainedfromtheprevioustablesandcurrenttablesareinmostcases<0.002,whichiswellwithintheexpectedexperimentalerrorsresultedfromtheinheritederrorsinestimatingthematchingwavelengths.Infact,becausethedispersioncoefficientsofbetweenα(1.161)andγ(1.174)aresonegligiblethattheywerecombinedintoasingletableintheaboveAmericanMineralogistpaper.Thesameistrueforchrysotileandamosite.
Shu-ChunSu,Ph.D.
NVLAPTechnicalExpert
BulkandAirborneAsbestosAnalysisPrograms
Introduction
Refractiveindex(RI)isthemostimportantopticalpropertiesofnon-opaqueminerals.Itisalsotheleadingdiagnosticopticalpropertyusedtoidentifyasbestoscomponentsinbulkinsulationorbuildingmaterialsbypolarizedlightmicroscopy(PLM)usingoilimmersionmethod(PerkinsandHarvey,1993).MostenvironmentallaboratoriesintheUnitedStatesparticipateintheNationalVoluntaryLaboratoryAccreditationProgram(NVLAP)administeredbytheNationalInstituteofStandardsandTechnology(NIST),U.S.DepartmentofCommerce.NVLAPrequirestherefractiveindicesαandγofasbestosfiberstobedeterminedandrecordedduringroutinebulkasbestossampleanalysis.Generally,anattainableandreasonableaccuracyis0.005forchrysotile,amosite,tremolite,actinolite,andanthophyllite,or0.010forcrocidolite.
Inmanyenvironmentallaboratories,thehighvolumeofsamplesdemandsanalyststominimizetheamountoftimespentonthedeterminationofrequiredopticalproperties,particularlytherefractiveindices.Itismostdesirabletodeterminebothαandγfromasingleslideorapreparation(Su,1993).Amongthethreemethodsforassessingthedirectionandmagnitudeofthemismatchbetweenasolidandasurroundingliquid,Beckeline(Bloss,1961),dispersionstaining(McCrone,1987),andobliqueillumination(StoiberandMorse,1994),onlythelatertwo,i.e.,dispersionstaining(DS)andobliqueillumination(OI),canmeetthespecificneedsfortheroutinePLManalysisofbulkasbestossamplesincommercialenvironmentallaboratories.TheadvantageofOImethodisthatitisassimpleandaccurateasDSanddoesnotrequirespecialobjectivelens.Inthemeantime,itcanbeappliedusinghighpowerobjectivelens(20X,40X,etc.)
ThispaperprovidesarapidandaccurateproceduretoenablebulkasbestosanalyststoconvertanobservedDScolorassociatedwithαorγforaspecificasbestosmineralinaspecificimmersionliquidthroughitscorrespondingmatchingwavelength(λ0)intocorrespondingnumericalRIvalue.
Procedure
1.Selectaproperimmersionliquidtomountthesample
MountthesuspectedasbestosfibersinanappropriateliquidaccordingtoTable1.Forasbestostypesotherthanchrysotile,therearetwochoicesofimmersionliquids.Thefirstchoice,whichistheliquidoutsidetheparentheses,giveshigheraccuracythanthesecondchoice,whichistheliquidinsidetheparentheses.Forexample,whenmeasuringcrocidolite,1.700liquidisamuchbetterchoicethan1.680.Forroutineanalysis,1.550(forchrysotile),1.620(fortremolite,actinolite,andanthophyllite),and1.700(foramositeandcrocidolite)arequiteadequatetoobtaingoodaccuracyforbothαandγ.Whenhigheraccuracyisdesirable(forexample,whenperformingNVLAPProficiencyTesting),otherliquidsmaybemoreappropriateanddifferentliquidsmaybeusedforαandγ.Forexample,use1.615fortheαand1.635fortheγofanthophyllite.Therefore,additionaltablesareincludedforhigheraccuracywork.
Itisimperativetohavefreshsurfaceofasbestosfibersindirectcontactwiththesurroundingliquid.Sometimes,thesurfaceofanasbestosbundlemaybecoatedbymatrixorbindermaterials.Inthiscase,trueDScolorsintrinsictotheasbestos/liquidcombinationmightnotbedisplayed.
Table1.TheSelectionofImmersionLiquidsforAsbestosAnalysis
SuspectedAsbestos
ImmersionLiquids(ConversionTableNumber)
Type
RI
ProficiencyTestingSamples
(Differentliquidsforαandγ)
RoutineSamples
(Sameliquidforbothαandγ)
Chrysotile
α
1.550(4A/B)
γ
Grunerite
(Amosite)
α
1.680(5A)
1.700(6A/B)
[2ndchoice1.680(5A/B)]
γ
1.700(6B)
Riebeckite
(Crocidolite)
α
1.700(8A)
1.700(8A/B)[or1.680(7A/B)]
γ
Tremolite
α
1.605(9A)
1.620(11A/B)
[2ndchoice1.625(12A/B)]
γ
1.6351(14B)
Actinolite
α
1.6101(16A)
1.625(19A/B)
[2ndchoice1.620(18A/B)]
γ
1.6401(22B)
Anthophyllite
α
1.6151(25A)
1.625(27A/B)
[2ndchoice1.620(26A/B)]
γ
1.6351(29B)
1.Cargillemakestwoseriesofimmersionliquidsintherangeof1.500to1.640:
SeriesA(normaldispersion),whichisinincrementof0.002,andSeriesE(highdispersion),whichisinincrementof0.005.Alloilsbetween1.605and1.640usedtogeneratetheconversiontablesinthispaperareSeriesEliquids.Fortremolite,actinolite,andanthophyllite,thecentral-stopDScolorsproducedbytheseSeriesEhighdispersionliquidsaremoreintenseandvividthanthoseproducedbySeriesAliquids.Tables9to27arenotapplicableifSeriesAliquidsareusedinstead.
2.Forqualitativeanalysis,1.605liquidissomehowokayfortremolite,actinolite,andanthophyllite.WhenaccurateRImeasurementisrequired,1.605liquidshouldbeavoidedbecausetheirγaresignificantlyhigherthan1.605andexhibityellowtopaleyellowcentral-stopDScolors.TheinherenterrorinconvertingDScolorstoλ0isalwayshigherintherangeofyellowthanintherangeofbluetoorange.
AsimpleandeffectivewaytobringoutthetrueDScolorsistogrindorrubthefiberbundlewithaneedleorprobetobreakthefiberbundleintofinerbundlessothatfreshsurfaceisrevealedandmadeindirectcontactwiththesurroundingliquid.
2.Measurethetemperatureoftheimmersionliquid
Measureandrecordt(inC),thetemperatureoftheimmersionliquidonthemicroscopeslide.Ifthetemperatureoftheliquid,slide,coverglassandsamplecanbereasonablyassumedtobeinequilibriumwiththeroomtemperature,tcanbeassumedtobeequaltotheroomtemperature.Thetemperaturedataisneededformakingtemperaturecorrection.Certainmicroscopetendstoheatuptheslide,resultinginanincrease2ormoreintheliquidtemperature.
3.Checkthealignmentofthepolarizedlightmicroscope
Makesurethatthepolarizedlightmicroscopeisproperlyaligned:
-DSobjectiveanditscentralstopiscentered;
-substagecondenseriscentered(ifpossible,setthemicroscopetoKöhlerillumination);
-thevibration(orprivileged)directionsofpolarizerandanalyzerareparalleltotheE-WandN-Scrosshairsintheeyepiece,respectively.
4.Observethecentral-stopDScolorassociatedwithαoftheasbestosfibers
AssumingthatthepolarizerisparalleltotheE-Wcrosshair,rotatethemicroscopestageuntilafiberbundleisparalleltotheE-WcrosshairiftheasbestosissuspectedtobecrocidoliteorperpendiculartotheE-Wcrosshairiftheasbestosissuspectedtobeotherfiveasbestostypes(chrysotile,tremolite,actinolite,anthophyllite,andamosite).Althoughtheαofmonoclinicamphiboles(tremoliteandactinolite)isnotexactlyperpendiculartothefiberelongation,theRIatthisorientationcanbeassumedtobereasonablyclosetoα.AdjusttheaperturediaphragmandfielddiaphragmtooptimizetheDScolordisplayedbytheasbestosfibers.
Usually,arangeofDScolorisdisplayed.MakesurethattheDScolorthatgivesthelowestRIisobserved,i.e.theDScolorcorrespondingtothelongestλ0.Forexample,iftheDScolorrangesfrombluetolightblue,chooselightblue.
5.CoverttheobservedDScolorintocorrespondingmatchingwavelength,λ0,betweentheasbestosfiberandtheimmersionliquidusedbyreferringtoFigure1orTable2
6.Findoutthenumericalvalueofαcorrespondingtotheobservedλ0andt
Refertooneoftheconversiontablestoconvertλ0andtintothecorrespondingrefractiveindex.Noticethateachtableisforaspecificdirection(αorγ)ofaspecificasbestosmineralmountedinaspecificRIliquid.IfanRIliquidwithadifferentnDand/oradifferentdispersioncoefficient[nF-nC]isused,thecurrenttablesarenolongerapplicable.Inthiscase,anewtablemaybecalculatedbyusinganExcelprogramwrittenbytheauthor,whichisavailableuponrequest.ThealgorithmusedtocomputeallconversiontablesinthispapercanbefoundinSu(1993and2003).The1993referenceisincludedinthisSOPasanAppendix.
7.ObservetheDScolorassociatedwithγoftheasbestosfibers
Rotatethemicroscopestage90andthenrepeatSteps4-6todetermineγ.Again,arangeofDScolorisusuallydisplayed.MakesurethattheDScolorthatgivesthehighestRIisobserved,i.e.theDScolorcorrespondingtotheshortestλ0.Fo
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