ISO 15248-1998 Zinc sulfide concentrates - Determination of silver and gold contents - Fire assay and flame atomic absorption spectrometric method using scorifi.pdf

1、A Referencenumbe r ISO15248:1998 (E) INTERNATIONAL STANDARD ISO 15248 Firstedition 19981201 ZincsulfideconcentratesDetermination ofsilverandgoldcontentsFireassay andflameatomicabsorptionspectrometric methodusingscorificationorcupellation ConcentrssulfursdezincDosagedelargentetdelorMthode parvoiesche

2、etspectromtriedabsorptionatomiquedanslaflamme partirdunescorificationoudunecoupellationISO15248:1998(E) ISO1998 Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyformorbyan ymeans,electronic ormechanical,includingphotocopyingandmicrofilm,withoutpermissio

3、ninwritingfromthepublisher. InternationalOrganizationforStandardization Casepostale56 CH1211Genve20 Switzerland Internet isoiso.ch PrintedinSwitzerland ii Contents Page 1Scope 1 2Normativereferences . .1 3Principle 1 4Reagents. 2 5Apparatus .3 6Sample . .4 7Procedure .4 8Expressionofresults 9 9Preci

4、sion .10 10Testreport . .12 AnnexA (normative) Procedureforthepreparationanddeterminationofthemassofapredriedtestportion13 AnnexB (normative) Trialfusion. 15 AnnexC (normative) Blankdetermination .16 AnnexD(normative)Flowsheetoftheprocedurefortheacceptanceofanalyticalvaluesforthetest samples17 Annex

5、E (informative) Derivationofprecisionequations .18 AnnexF (informative) Bibliography.25ISO ISO15248:1998(E) iii Foreword ISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISO memberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutth

6、roughISOtechnical committees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhas therighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnongovernmental,in liaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrote

7、chnical Commission(IEC)onallmattersofelectrotechnicalstandardization. DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting. PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote. InternationalStandardISO15248wasprep

8、aredbyTechnicalCommitteeISO/TC183, Copper,leadandzincores. AnnexesAtoDformanintegralpartofthisInternationalStandard,annexesEandFareforinformationonly.INTERNATIONALSTANDARD ISO ISO15248:1998(E) 1 ZincsulfideconcentratesDeterminationofsilverandgold contentsFireassayandflameatomicabsorptionspectrometri

9、c methodusingscorificationorcupellation 1Scope ThisInternationalStandardspecifiesafireassayandflameatomicabsorptionspectrometricprocedureforthe determinationofsilverandgoldcontentsofzincsulfideconcentrates. Themethodisapplicabletothedeterminationofsilverandgoldinzincsulfideconcentratescontainingupto

10、 60%( m/m)zincintheformofzincblendeandrelatedmaterials. Themethodisapplicabletosilvercontentsfrom10g/tto500g/tandgoldcontentsfrom0,1g/tto12g/t. 2Normative references Thefollowingstandardscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthis Internationalstandard.Atthetimeofpub

11、lication,theeditionsindicatedwerevalid.Allstandardsaresubjectto revision,andpartiestoagreementsbasedonthisInternationalStandardareencouragedtoinvestigatethe possibilityofapplyingthemostrecenteditionsofthestandardsindicatedbelow.MembersofIECandISOmaintain registersofcurrentlyvalidInternationalStandar

12、ds. ISO3851:1984, LaboratoryglasswareBurettesPart1:Generalrequirements . ISO648:1977, LaboratoryglasswareOnemarkpipettes . ISO1042:1998, LaboratoryglasswareOnemarkvolumetricflasks . ISO3696:1987, WaterforanalyticallaboratoryuseSpecificationandtestmethods . ISO4787:1984, LaboratoryglasswareVolumetric

13、glasswareMethodsforuseandtestingofcapacity . ISO9599:1991,Copper,leadandzincsulfideconcentratesDeterminationofhygroscopicmoistureinthe analysissampleGravimetricmethod . 3Principle 3.1Scorification Fireassayfusionofatestportiontoproducealeadbutton,whichisscorifiedtoreduceittoamassof2gto5g. Retreatmen

14、tfusionoftheprimaryfusionandscorificationslagstoproducealowsilvercontentleadbuttonwhichis scorifiedtoapproximately2gto5g. Dissolutionofbothleadbuttonsinnitricacidandfiltrationofthesolution.Dissolutionofthefilterpaperplusgoldand determinationofsilverandgoldbyflameatomicabsorptionspectrometry.ISO15248

15、:1998(E) ISO 2 3.2Cupellation Fireassayfusionofatestportiontoproducealeadbutton,whichiscupelledtoproduceabeadofsilverandgold. Retreatmentfusionoftheprimaryfusionslagandspentcupeltoproduceasecondbeadofsilverandgold. Dissolutionofbothbeadsindilutenitricacidandfiltrationofthesolution.Dissolutionofthefi

16、lterpaperplusgoldand determinationofsilverandgoldbyflameatomicabsorptionspectrometry. 4Reagents Duringtheanalysis,useonlyreagentsofarecognizedanalyticalgradeandwaterthatcomplieswithgrade2of ISO3696.Washallglasswarewithaquaregiafollowedbywaterand25%ammonia.Achloridefreeenvironmentis recommended. 4.1

17、Sodiumcarbonate, anhydrous 4.2 Litharge,assayreagentgradehavingsilvercontentlessthan0,2g/t,andgoldcontentlessthan0,01g/t 4.3 Silica,precipitatedgrade 4.4 Potassiumnitrateorsodiumnitrate 4.5 Flour 4.6 Nitricacid ( r 20 1,42g/ml),chloridecontent0,5 m g/ml 4.7 Nitricacidwashsolution, (5ml/l) To995mlofw

18、ateradd5mlofnitricacid(4.6). 4.8 Nitricacid ,(250ml/l) To1500mlofwatercarefullyadd,withstirring,500mlofnitricacid(4.6)andcool. 4.9 Hydrochloricacid ,( r 20 1,16g/mlto1,19g/ml). 4.10 Borax,fusedanhydroussodiumtetraborate 4.11 Silvermetal, minimum99,99%purity 4.12 Goldmetal ,minimum99,99%purity 4.13 A

19、quaregia Mix3partsofhydrochloricacid(4.9)with1partofnitricacid(4.6);preparefreshlyasrequired. 4.14 Ammoniasolution Add500mlofammoniasolution( r 20 0,89g/ml)to500mlofwater. 4.15 Standardsolutions NOTE Standardsolutionsshouldbepreparedatthesameambienttemperatureasthatatwhichthedeterminationswillbe con

20、ducted.ISO ISO15248:1998(E) 3 4.15.1 Silverstandardsolutions 4.15.1.1 Silverstandardsolution, (1000 m g/ml) Weigh0,5000gofsilvermetal(4.11)intoa400mlbeaker,add100mlofnitricacid(4.8),coverandheatgently untilthemetaldissolves.Continueheatingtoremoveoxidesofnitrogen.Cool,andtransfertoa500mlvolumetric f

21、lask.Dilutetovolumewithwaterandmixthoroughly. Thissolutionshouldbestoredinabrownbottle. 4.15.1.2 Silverstandardsolution, (50 m g/ml) Pipette10mlofsilverstandardsolution(4.15.1.1)intoa200mlvolumetricflask,add40mlofnitricacid(4.8),dilute tovolumeandmixthoroughly. Thissolutionshouldbestoredinabrownbott

22、le. 4.15.2 Goldstandardsolutions 4.15.2.1 Goldstandardsolution, (1000 m g/ml) Weigh0,100gofgoldmetal(4.12)intoa50mlbeaker,add5mlofaquaregiasolution(4.13),coverandheatto dissolvethegold.Washandremovethecoverandevaporatetoneardryness(donotallowtogotodryness,as goldmayprecipitate.)Cool,add5mlofhydrochl

23、oricacid(4.9),transferthesolutionquantitativelytoa100ml volumetricflask,dilutetovolumewithwater,stopperandmixthoroughly.Storethesolutioninabrownbottle. 4.15.2.2 Goldstandardsolution, (100 m g/ml) Pipette20mlofgoldstandardsolution(4.15.2.1)intoa100mlvolumetricflask,add10mlofhydrochloricacid(4.9), dil

24、utetovolumewithwater,stopperandmixthoroughly. 4.16 Calibrationsolutions NOTE Calibrationsolutionsshouldbepreparedatthesameambienttemperatureasthatatwhichthedeterminationswill beconducted. 4.16.1 Silvercalibrationsolutions Tofive100mlvolumetricflasks,addfromaburette(5.6)0ml,2ml,4ml,6mland8mlofsilvers

25、tandardsolution (4.15.1.2);add20mlofnitricacid(4.8),dilutetovolumewithwaterandmixthoroughly. Thesestandardscontain0 m g,1 m g,2 m g,3 m gand4 m gofsilverpermlandshallbefreshlyprepared. 4.16.2 Goldcalibrationsolutions Tosix100mlvolumetricflasks,addfromaburette(5.6)0ml,2ml,4ml,6ml,8mland10mlofgoldstan

26、dard solution(4.15.2.2);add10mlofaquaregiasolution(4.13),dilutetovolumewithwaterandmixthoroughly. Thesestandardscontain0 m g,2 m g,4 m g,6 m g,8 m gand10 m gofgoldpermlandshallbefreshlyprepared. 5Apparatus Ordinarylaboratoryequipmentplusthefollowing. 5.1 Volumetricglassware, ofclassAcomplyingwithISO

27、3851,ISO648andISO1042andusedinaccordance withISO4787. 5.2 Conventionalfireassayequipment 5.2.1 Assaycruciblefurnace, havingamaximumrequiredoperatingtemperatureof1100 C. 5.2.2 Mufflefurnace,havingamaximumrequiredoperatingtemperatureof1100 C;temperatureindication, automatictemperaturecontrolandcontrol

28、ledairflowaredesirable.ISO15248:1998(E) ISO 4 5.2.3 Crucibles,madeoffireclay,ofnominalcapacity300mlto500ml,capableofwithstandingcorrosionbythe sampleandfluxesat1050 C.Thecrucibleshallbeofsuchasizethatthechargedoesnotfillthecrucibletoa depthofgreaterthan3/4thedepthofthecrucible. 5.2.4 Scorifiers,made

29、offireclay,ofapproximately75mmdiameter,preferablynotshallowform. 5.2.5 Cupels,madeofmagnesiumoxide,orboneashcupelshavinganominalcapacityof50gofmoltenlead. Theinsidebottomofthecupelshallbeconcave. 5.2.6 Conicalmould ,madeofcastiron,ofsufficientcapacitytocontainallofthemoltenleadplusslagfromthe crucib

30、lefusion. 5.2.7 Pulverizer 5.3 Balances 5.3.1 Toploading, capableofbeingreadto1mg 5.3.2 Precisionanalytical ,capableofbeingreadto0,1mg 5.4 Atomicabsorptionspectrometer(AAS) ,equippedwithbackgroundcorrectionandaglassbeadinthespray chamberratherthanaflowspoiler 5.5 Filtrationequipment 5.5.1 Membranefi

31、ltercellulosenitrate/celluloseacetate, diameter25mm,meshsize0,45 m m 5.5.2 Vacuumflask ,of250mlcapacity,buchnerfilterflaskhavingawideneck 5.5.3 Membranefilterfunnel ,suitableforusewith25mmmembranefilters 5.6 Burette,Agrade10mlcapacity,capableofbeingreadto0,02ml 6Sample 6.1Test sample Prepareanairequ

32、ilibratedtestsampleinaccordancewithISO9599. NOTE Atestsampleisnotrequiredifpredriedtestportionsaretobeused(seeannexA). 6.2Test portion Takingmultipleincrements,extractatestportionfromthetestsampleinsuchamannerthatitisrepresentativeof thewholecontentsofthedishortray.Weightothenearest0,1mgapproximatel

33、y20goftestsample.Atthesame timeasthetestportionisweighed,weightestportionsforthedeterminationofhygroscopicmoistureinaccordance withISO9599. Alternatively,themethodspecifiedinannexAmaybeusedtopreparepredriedtestportionsdirectlyfromthe laboratorysample. 7Procedure 7.1 Numberofdeterminations Carryoutth

34、edeterminationsatleastinduplicate,asfaraspossibleunderrepeatabilityconditions,oneachtest sample. NOTE Repeatabilityconditionsexistwheremutuallyindependenttestresultsareobtainedwiththesamemethodon identicaltestmaterialinthesamelaboratorybythesameoperatorusingthesameequipmentwithinshortintervalsoftime

35、.ISO ISO15248:1998(E) 5 7.2Trial fusion CarryoutatrialfusionasdescribedinannexBtoensurethatthemassoftheleadbuttonisbetween28gand35g. NOTE Itisessentialthatthistrialfusionbeperformed. 7.3Blank tests CarryoutaduplicatereagentblanktestasdescribedinannexCinparallelwitheachbatchofsamplesfired,using thesa

36、mequantitiesofallreagentswiththeadditionofsufficientflour(4.5)tothefluxtogiveabuttonsizeof28gto 35g.Omitthesampleandthepotassiumnitrate. NOTE Iftheblanksolutions(annexC)exceed0,05 m g/mlforgold,thereagentsshouldbecheckedandtheproblem rectified.Otherwisetheblankissubtractedfromtheresult. 7.4Charge pr

37、eparation Determinethemassofpotassiumnitrate(4.4)requiredinthechargeasindicatedbythetrialfusion(seeannexB) andincludethisreagentinthefluxmixture(seetable1). Thoroughlymixthetestportionwithafluxofthecompositionspecifiedintable1. Table1Recommendedmassesoffluxcomponentsforpreparationofcharges Fluxcompo

38、nents Mass g Sodiumcarbonate(4.1) 30 Litharge(4.2) 120 Silica(4.3) 10 Borax(4.10) 10 Potassiumnitrate(4.4) Placethemixtureintheassaycrucible(5.2.3). NOTE1 Theintimatemixingoffluxesandsamplesisveryimportant.Allfluxcomponentsshouldbeinafinelydividedstate, withapreferredparticlesizeoflessthan0,5mm. NOT

39、E2 Thequantitiesofoxidizingreagentinthemixturearedependentuponthereducingpowerofthetestsample.The trialfusion(seeannexB)willdeterminethemassofpotassiumnitratenecessarytoyieldabuttonofmass28gto35g.The oxidizingreagentshouldnotbeincludedinabulkflux.Itshouldbeweighedupindividuallytoensuretherepeatabili

40、tyofth e massoftheleadbutton,which,iffusionconditionsareuniformlyrepeated,shouldagreewithin1goflead,thusdecreasing thevariabilityoffinishingtimesofscorificationorcupellation. NOTE3 Ifdifficultiesareexperiencedinproducingrepeatableandpredictablemassesofleadbutton,alidforthecrucible maybeofassistance.

41、 7.5Primary fusion Placethecrucibleinthefurnace(5.2.1)preheatedtoapproximately900 C. Slowlyraisethefurnacetemperatureto1050 C.Maintainthistemperatureuntilfusionhasbeencalmforatleast 10min. Pourthefusionintoadryconicalmould(5.2.6),takingcaretoensurethatnolossofleadorslagoccurs.Reserve thecrucibleforr

42、etreatmentfusion. Allowthemixturetocoolandcarefullyseparatetheleadbuttonfromtheslag.Hammertheleadbuttonas necessarytoremoveanysmallparticlesofadheringslag.Reservetheslagforretreatment.ISO15248:1998(E) ISO 6 Weightheleadbutton.Ifthebuttonweighslessthan28gormorethan35g,discardthebuttonandslagandrepeat theassayusinglessoxidizingagentor