ISO 13658:2000
(Main)Zinc sulfide concentrates — Determination of zinc content — Hydroxide precipitation and EDTA titrimetric method
Zinc sulfide concentrates — Determination of zinc content — Hydroxide precipitation and EDTA titrimetric method
This International Standard specifies a hydroxide precipitation and EDTA titrimetric method for the determination of the zinc content of zinc ores and concentrates containing 10 % (m/m) to 60%(m/m) zinc.
Concentrés sulfurés de zinc — Dosage du zinc — Méthode par précipitation d'hydroxydes et titrage à l'EDTA
Koncentrati cinkovega sulfida - Določevanje cinka - Hidroksidna sedimentacija in titrimetrijska metoda z EDTA
General Information
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Concentrés sulfurés de zinc -- Dosage du zinc -- Méthode par précipitation d'hydroxydes et titrage à l'EDTAZinc sulfide concentrates -- Determination of zinc content -- Hydroxide precipitation and EDTA titrimetric method73.060.99Druge rudeOther metalliferous mineralsICS:Ta slovenski standard je istoveten z:ISO 13658:2000SIST ISO 13658:2001en01-junij-2001SIST ISO 13658:2001SLOVENSKI
STANDARD
ReferencenumberISO13658:2000(E)©ISO2000INTERNATIONALSTANDARDISO13658Firstedition2000-03-15Zincsulfideconcentrates—Determinationofzinccontent—HydroxideprecipitationandEDTAtitrimetricmethodConcentréssulfurésdezinc—Dosageduzinc—Méthodeparprécipitationd'hydroxydesettitrageàl'EDTASIST ISO 13658:2001
ISO13658:2000(E)PDFdisclaimerThisPDFfilemaycontainembeddedtypefaces.InaccordancewithAdobe'slicensingpolicy,thisfilemaybeprintedorviewedbutshallnotbeeditedunlessthetypefaceswhichareembeddedarelicensedtoandinstalledonthecomputerperformingtheediting.Indownloadingthisfile,partiesacceptthereintheresponsibilityofnotinfringingAdobe'slicensingpolicy.TheISOCentralSecretariatacceptsnoliabilityinthisarea.AdobeisatrademarkofAdobeSystemsIncorporated.DetailsofthesoftwareproductsusedtocreatethisPDFfilecanbefoundintheGeneralInforelativetothefile;thePDF-creationparameterswereoptimizedforprinting.EverycarehasbeentakentoensurethatthefileissuitableforusebyISOmemberbodies.Intheunlikelyeventthataproblemrelatingtoitisfound,pleaseinformtheCentralSecretariatattheaddressgivenbelow.©ISO2000Allrightsreserved.Unlessotherwisespecified,nopartofthispublicationmaybereproducedorutilizedinanyformorbyanymeans,electronicormechanical,includingphotocopyingandmicrofilm,withoutpermissioninwritingfromeitherISOattheaddressbeloworISO'smemberbodyinthecountryoftherequester.ISOcopyrightofficeCasepostale56CH-1211Geneva20Tel.+41227490111Fax+41227341079E-mailcopyright@iso.chWebwww.iso.chPrintedinSwitzerlandii©ISO2000–AllrightsreservedSIST ISO 13658:2001
ISO13658:2000(E)©ISO2000–AllrightsreservediiiContentsPageForeword.iv1Scope.12Normativereferences.13Principle.24Reagents.25Apparatus.36Sample.37Procedure.48Expressionofresults.69Applicationtothetradingofzincconcentrates.710Accuracy.711Testreport.8AnnexA(informative)Anexaminationofpotentiallyinterferingelements.9AnnexB(normative)Procedureforthepreparationanddeterminationofthemassofapredriedtestportion.10AnnexC(normative)Determinationofzinccontentofacid-insolubleandhydroxideprecipitationresiduesbyatomicabsorptionspectroscopy.12AnnexD(normative)Determinationofcadmiumbyatomicabsorptionspectrometry.15AnnexE(normative)Flowsheetoftheprocedurefortheacceptanceofanalyticalvaluesfortestsamples.18AnnexF(informative)Derivationofprecisionequations.19SIST ISO 13658:2001
ISO13658:2000(E)iv©ISO2000–AllrightsreservedForewordISO(theInternationalOrganizationforStandardization)isaworldwidefederationofnationalstandardsbodies(ISOmemberbodies).TheworkofpreparingInternationalStandardsisnormallycarriedoutthroughISOtechnicalcommittees.Eachmemberbodyinterestedinasubjectforwhichatechnicalcommitteehasbeenestablishedhastherighttoberepresentedonthatcommittee.Internationalorganizations,governmentalandnon-governmental,inliaisonwithISO,alsotakepartinthework.ISOcollaboratescloselywiththeInternationalElectrotechnicalCommission(IEC)onallmattersofelectrotechnicalstandardization.InternationalStandardsaredraftedinaccordancewiththerulesgivenintheISO/IECDirectives,Part3.DraftInternationalStandardsadoptedbythetechnicalcommitteesarecirculatedtothememberbodiesforvoting.PublicationasanInternationalStandardrequiresapprovalbyatleast75%ofthememberbodiescastingavote.AttentionisdrawntothepossibilitythatsomeoftheelementsofthisInternationalStandardmaybethesubjectofpatentrights.ISOshallnotbeheldresponsibleforidentifyinganyorallsuchpatentrights.InternationalStandardISO13658waspreparedbyTechnicalCommitteeISO/TC183,Copper,leadandzincoresandconcentrates.AnnexesB,C,DandEformanormativepartofthisInternationalStandard.AnnexesAandFareforinformationonly.SIST ISO 13658:2001
INTERNATIONALSTANDARDISO13658:2000(E)©ISO2000–Allrightsreserved1Zincsulfideconcentrates—Determinationofzinccontent—HydroxideprecipitationandEDTAtitrimetricmethodWARNING—ThisInternationalStandardmayinvolvehazardousmaterials,operationsandequipment.ItistheresponsibilityoftheuserofthisInternationalStandardtoestablishappropriatehealthandsafetypracticesanddeterminetheapplicabilityofregulatorylimitationspriortouse.1ScopeThisInternationalStandardspecifiesahydroxideprecipitationandEDTAtitrimetricmethodforthedeterminationofthezinccontentofzincoresandconcentratescontaining10%(m/m)to60%(m/m)zinc.2NormativereferencesThefollowingnormativedocumentscontainprovisionswhich,throughreferenceinthistext,constituteprovisionsofthisInternationalStandard.Fordatedreferences,subsequentamendmentsto,orrevisionsof,anyofthesepublicationsdonotapply.However,partiestoagreementsbasedonthisInternationalStandardareencouragedtoinvestigatethepossibilityofapplyingthemostrecenteditionsofthenormativedocumentsindicatedbelow.Forundatedreferences,thelatesteditionofthenormativedocumentreferredtoapplies.MembersofISOandIECmaintainregistersofcurrentlyvalidInternationalStandards.ISO385-1:1984,Laboratoryglassware—Burettes—Part1:Generalrequirements.ISO648:1977,Laboratoryglassware—One-markpipettes.ISO1042:1998,Laboratoryglassware—One-markvolumetricflasks.ISO3696:1987,Waterforanalyticallaboratoryuse—Specificationandtestmethods.ISO4787:1984,Laboratoryglassware—Volumetricglassware—Methodsforuseandtestingofcapacity.ISO5725-2:1994,Accuracy(truenessandprecision)ofmeasurementmethodsandresults—Part2:Basicmethodforthedeterminationofrepeatabilityandreproducibilityofastandardmeasurementmethod.ISO9599:1991,Copper,leadandzincsulfideconcentrates—Determinationofhygroscopicmoistureintheanalysissample—Gravimetricmethod.ISO12739:1997,Zincsulfideconcentrates—Determinationofzinccontent—Ion-exchange/EDTAtitrimetricmethod.ISO13291:1997,Zincsulfideconcentrates—Determinationofzinccontent—SolventextractionandEDTAtitrimetricmethod.ISO/Guide35:1989,Certificationofreferencematerials—Generalandstatisticalprinciples.SIST ISO 13658:2001
ISO13658:2000(E)2©ISO2000–Allrightsreserved3PrincipleDissolutionofatestportionofzincconcentrateinbromineandnitricacid.Dissolutionofanyremaininginsolubleresidueinhydrofluoricandsulfuricacids.Separationofaluminium,ironandmanganeseashydroxidesusingprecipitationwithammonia,ammoniumchlorideandammoniumpersulfate.Separationofleadassulfate.Copperismasked.Determinationofzincandcadmiumtogetherbycomplexometrictitration(pH5,5to5,7)inthepresenceofxylenolorange.Independentdeterminationofcadmiumandsubtractionfromthezincvalue.NOTEAnexaminationofpotentialinterferingelementsiscontainedinannexA.4ReagentsDuringtheanalysis,useonlyreagentsofrecognizedanalyticalreagentgradeandwaterthatcomplieswithgrade2ofISO3696.4.1Zincmetal,minimumpurity99,99%Thesurfaceofthemetalshallbefreefromoxidepriortouseandmaybecleanedbyimmersingthemetalinhydrochloricacid(4.6)for1min,washingwellwithwaterfollowedbyanacetonerinseanddriedinanovenat50C.4.2Ammoniumchloride4.3Bromine4.4Nitricacid(201,42g/ml)4.5Hydrochloricacid(201,16g/mlto1,19g/ml)4.6Hydrochloricacid(1+1)Add500mlofhydrochloricacid(4.5)to500mlofwater.4.7Sulfuricacid(201,84g/ml)4.8Dilutesulfuricacid(1+1)Addcarefullyandslowlywithstirring,500mlofsulfuricacid(4.7)to500mlofwater.4.9Sulfuricacid(1+99)Add20mlofsulfuricacid(4.8)to1000mlofwater.4.10Ammonia(200,89g/ml)4.11Ammoniumpersulfate4.12AmmoniawashingsolutionDissolve20gofammoniumchloridein1000mlofaqueousammoniasolution(1+100).4.13Ethanol,pureordenatured4.14Aceticacid(201,05g/ml)SIST ISO 13658:2001
ISO13658:2000(E)©ISO2000–Allrightsreserved34.15Bromothymolblueindicatorsolution(1g/l)Dissolve0,1gofbromothymolblueinethanol(4.13)anddiluteto100ml.4.16Hexamethylenetetraminebuffersolution(250g/l)Dissolve250gofhexamethylenetetramine(hexamine)inwater.Add60mlofaceticacid(4.14)anddiluteto1l.4.17MaskingsolutionDissolve50gofammoniumfluorideand100gofsodiumthiosulfatepentahydrateinwateranddiluteto1l.4.18Xylenolorangeindicatorsolution(1g/l)Dissolve0,1gofthesodiumsaltofxylenolorangeinwateranddiluteto100ml.4.19Iron(III)solution(10mgFe/ml)Dissolve72,3gofiron(III)nitratenonahydrateinwateranddiluteto1l.4.20EDTAstandardsolution(0,1mol/l)Dissolve37,2gofthedi-sodiumsaltofethylenediaminetetraaceticacidand2gofsodiumhydroxideinwateranddiluteto1l.5Apparatus5.1ClassAvolumetricglassware,complyingwithISO385-1,ISO648andISO1042andusedinaccordancewithISO4787.5.2Balance,capableofbeingreadto0,1mg.5.3Laboratoryhotplate5.4pHmeter6Sample6.1TestsamplePrepareanair-equilibratedtestsampleinaccordancewithISO9599.NOTEAnair-equilibratedtestsampleisnotrequiredifpredriedtestportionsaretobeused(seeannexB).6.2TestportionTakingmultipleincrements,extractatestportionof0,5gfromthetestsampleandweightothenearest0,1mg.Atthesametimeasthetestportionsaretakenforanalysis,weightestportionsforthedeterminationofhygroscopicmoistureinaccordancewithISO9599.Alternatively,themethodspecifiedinannexBmaybeusedtopreparepredriedtestportionsdirectlyfromthelaboratorysample.SIST ISO 13658:2001
ISO13658:2000(E)4©ISO2000–Allrightsreserved7Procedure7.1NumberofdeterminationsCarryoutthedeterminationsatleastinduplicate,asfaraspossibleunderrepeatabilityconditions,oneachtestsample.NOTERepeatabilityconditionsexistwheremutuallyindependenttestresultsareobtainedwiththesamemethodonidenticaltestmaterialinthesamelaboratorybythesameoperatorusingthesameequipmentwithinshortintervalsoftime.7.2ReagentblankAreagentblankshallbedetermined.Itisadvisabletoperformduplicateblankdeterminationseverytimeananalysisiscarriedoutonalaboratorysample.Theblanksamplesarecarriedthroughthewholeprocedure,withtheexceptionthatnolaboratorysampletestportionisrequired.TheaveragevolumeofEDTAtitrantusedforthereagentblanksisVb.7.3DissolutionDigestthesampleasfollows.Transferthetestportion(6.2)toa300mlconicalbeaker.Moistenthematerialwithabout5mlofwaterandadd1mlofbromine(4.3).Standfor15min,swirlingthebeakerandcontentsfromtimetotime.Cautiouslyadd15mlofnitricacid(4.4).Placethebeakeronahotplate(5.3)andheatgraduallyuntilbromineandnitrogenoxidesareexpelled.Add15mlofsulfuricacid(4.8).Heatandevaporatethesolutionuntiltheevolutionofsulfuricacidfumes(approximately5ml).NOTECareneedstobetakentoensurenolossofmaterialwhenfumingsamplescontainingsignificantcarbonaceousmaterial,duetothesampleclimbingupthewallsofthebeaker.Coolandcautiouslyaddabout50mlofwaterandheatthesolutionuntilboiling.Coolthesolutiontoroomtemperatureandfilteritintoa500mlconicalbeakerthroughamedium-speedcellulosefilterpaper.Washthebeakerandfilterpaperthoroughlywithsulfuricacid(4.9).Collectthefiltrateandwashingsolutioninthesamebeaker.Reservethefilterpaperandacid-insolubleresiduefordeterminationofzincbyFAAS(asdescribedinannexC)fortheconcentratebeinganalysedandtheanalystperformingthetest,unlessithasbeenstatisticallyshown,byprevioustesting,thatthezinciscompletelysolubleintheinitialdecomposition.Ifthisstepisnotroutinelyperformed,regularchecksconfirmingthevalidityofitsexclusionshallbecarriedoutforeachconcentratetypebyeachanalyst.Similarly,alldocumentationcontainingresultswherethisstephasbeenexcludedshallcontainacommentindicatingthisfact.7.4Separationofaluminium,ironandmanganeseashydroxidesAdd15gofammoniumchloride(4.2)tothesolutionandswirlgentlytodissolve.NOTE1Iftheironcontentofthesampleisonlyafewpercent,theniron(III)solution(4.19)isaddedtothesolutiontoincreasethecontainedironinsolutiontoabout50mg.Heattonearboilingthenaddammonia(4.10)tothesolutionuntilcompleteprecipitationoccursandthen30mlinexcess.Add1gofammoniumpersulfate(4.11)tothesolution,heatuntilboilingandcontinueboilingfor1min.Standtoallowtheprecipitatetosettleout.Filterintoanother500mlbeakerthroughamedium-speedcellulosefilterpaperandwashtheprecipitateseveraltimeswithhotammoniawashingsolution(4.12).Collectthefiltrateandthewashingsolutionsinthesamebeaker.NOTE2Filtrationwillbeslowforhighleadcontentsamples.SIST ISO 13658:2001
ISO13658:2000(E)©ISO2000–Allrightsreserved5Washtheprecipitatebackintotheoriginalbeakerwithoutdamagingthefilterpaperanddissolveitwith10mlofhydrochloricacid(4.6).Add5gofammoniumchloride(4.2)tothesolution.Repeattheprecipitationbyadditionofammonia(4.10)andammoniumpersulfate(4.11).Boil,filterthroughtheoriginalfilterpaperandwashinthesamemannerasdescribedabove.Collectthefiltrateandwashingsolutioninthesamebeakerusedtocollectthefiltrateforthefirstseparationandplacethebeakeronahotplate(5.3).Heatgentlyandevaporatethesolutiontoabout200ml.Cooltoroomtemperature.Keepthehydroxideprecipitateforlatertreatment.7.5Titration7.5.1DeterminationofthetitrationfactoroftheEDTAsolutionNOTE1Inordertoobtainarelativeaccuracyofbetween0,1%and0,2%,itisne
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INTERNATIONAL ISO
STANDARD 13658
First edition
2000-03-15
Zinc sulfide concentrates — Determination
of zinc content — Hydroxide precipitation
and EDTA titrimetric method
Concentrés sulfurés de zinc — Dosage du zinc — Méthode par
précipitation d'hydroxydes et titrage à l'EDTA
Reference number
©
ISO 2000
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ii © ISO 2000 – All rights reserved
Contents Page
Foreword.iv
1 Scope .1
2 Normative references .1
3 Principle.2
4 Reagents.2
5 Apparatus .3
6 Sample .3
7 Procedure .4
8 Expression of results .6
9 Application to the trading of zinc concentrates .7
10 Accuracy.7
11 Test report .8
Annex A (informative) An examination of potentially interfering elements .9
Annex B (normative) Procedure for the preparation and determination of the mass of a predried test
portion.10
Annex C (normative) Determination of zinc content of acid-insoluble and hydroxide precipitation
residues by atomic absorption spectroscopy.12
Annex D (normative) Determination of cadmium by atomic absorption spectrometry.15
Annex E (normative) Flowsheet of the procedure for the acceptance of analytical values for test
samples.18
Annex F (informative) Derivation of precision equations .19
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO
member bodies). The work of preparing International Standards is normally carried out through ISO technical
committees. Each member body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations, governmental and non-governmental, in
liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 3.
Draft International Standards adopted by the technical committees are circulated to the member bodies for voting.
Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 13658 was prepared by Technical Committee ISO/TC 183, Copper, lead and zinc ores
and concentrates.
Annexes B, C, D and E form a normative part of this International Standard. Annexes A and F are for information
only.
iv © ISO 2000 – All rights reserved
INTERNATIONAL STANDARD ISO 13658:2000(E)
Zinc sulfide concentrates — Determination of zinc content —
Hydroxide precipitation and EDTA titrimetric method
WARNING — This International Standard may involve hazardous materials, operations and equipment. It is
the responsibility of the user of this International Standard to establish appropriate health and safety
practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a hydroxide precipitation and EDTA titrimetric method for the determination of
the zinc content of zinc ores and concentrates containing 10 % (m/m)to 60% (m/m)zinc.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 385-1:1984, Laboratory glassware — Burettes — Part 1: General requirements.
ISO 648:1977, Laboratory glassware — One-mark pipettes.
ISO 1042:1998, Laboratory glassware — One-mark volumetric flasks.
ISO 3696:1987, Water for analytical laboratory use — Specification and test methods.
ISO 4787:1984, Laboratory glassware — Volumetric glassware — Methods for use and testing of capacity.
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method
for the determination of repeatability and reproducibility of a standard measurement method.
ISO 9599:1991, Copper, lead and zinc sulfide concentrates — Determination of hygroscopic moisture in the
analysis sample — Gravimetric method.
ISO 12739:1997, Zinc sulfide concentrates — Determination of zinc content — Ion-exchange/EDTA titrimetric
method.
ISO 13291:1997, Zinc sulfide concentrates — Determination of zinc content — Solvent extraction and EDTA
titrimetric method.
ISO/Guide 35:1989, Certification of reference materials — General and statistical principles.
3Principle
Dissolution of a test portion of zinc concentrate in bromine and nitric acid. Dissolution of any remaining insoluble
residue in hydrofluoric and sulfuric acids. Separation of aluminium, iron and manganese as hydroxides using
precipitation with ammonia, ammonium chloride and ammonium persulfate. Separation of lead as sulfate. Copper is
masked. Determination of zinc and cadmium together by complexometric titration (pH 5,5 to 5,7) in the presence of
xylenol orange. Independent determination of cadmium and subtraction from the zinc value.
NOTE An examination of potential interfering elements is contained in annex A.
4 Reagents
During the analysis, use only reagents of recognized analytical reagent grade and water that complies with grade 2
of ISO 3696.
4.1 Zinc metal, minimum purity 99,99 %
The surface of the metal shall be free from oxide prior to use and may be cleaned by immersing the metal in
hydrochloric acid (4.6) for 1 min, washing well with water followed by an acetone rinse and dried in an oven at
50 �C.
4.2 Ammonium chloride
4.3 Bromine
4.4 Nitric acid (� 1,42 g/ml)
4.5 Hydrochloric acid (� 1,16 g/ml to 1,19 g/ml)
4.6 Hydrochloric acid (1+1)
Add 500 ml of hydrochloric acid (4.5) to 500 ml of water.
4.7 Sulfuric acid (� 1,84 g/ml)
4.8 Dilute sulfuric acid (1+1)
Add carefully and slowly with stirring, 500 ml of sulfuric acid (4.7) to 500 ml of water.
4.9 Sulfuric acid (1 + 99)
Add 20 ml of sulfuric acid (4.8) to 1 000 ml of water.
4.10 Ammonia (� 0,89 g/ml)
4.11 Ammonium persulfate
4.12 Ammonia washing solution
Dissolve 20 g of ammonium chloride in 1 000 ml of aqueous ammonia solution (1 + 100).
4.13 Ethanol, pure or denatured
4.14 Acetic acid (� 1,05 g/ml)
2 © ISO 2000 – All rights reserved
4.15 Bromothymol blue indicator solution (1 g/l)
Dissolve 0,1 g of bromothymol blue in ethanol (4.13) and dilute to 100 ml.
4.16 Hexamethylenetetramine buffer solution (250 g/l)
Dissolve 250 g of hexamethylenetetramine (hexamine) in water. Add 60 ml of acetic acid (4.14) and dilute to 1 l.
4.17 Masking solution
Dissolve 50 g of ammonium fluoride and 100 g of sodium thiosulfate pentahydrate in water and dilute to 1 l.
4.18 Xylenol orange indicator solution (1 g/l)
Dissolve0,1gofthesodium saltofxylenolorangeinwateranddiluteto100ml.
4.19 Iron(III) solution (10mgFe/ml)
Dissolve 72,3 g of iron(III) nitrate nonahydrate in water and dilute to 1 l.
4.20 EDTA standard solution (0,1 mol/l)
Dissolve 37,2 g of the di-sodium salt of ethylenediaminetetraacetic acid and 2 g of sodium hydroxide in water and
dilute to 1 l.
5 Apparatus
5.1 Class A volumetric glassware, complying with ISO 385-1, ISO 648 and ISO 1042 and used in accordance
with ISO 4787.
5.2 Balance, capable of being read to 0,1 mg.
5.3 Laboratory hotplate
5.4 pH meter
6Sample
6.1 Test sample
Prepare an air-equilibrated test sample in accordance with ISO 9599.
NOTE An air-equilibrated test sample is not required if predried test portions are to be used (see annex B).
6.2 Test portion
Taking multiple increments, extract a test portion of 0,5 g from the test sample and weigh to the nearest 0,1 mg. At
the same time as the test portions are taken for analysis, weigh test portions for the determination of hygroscopic
moisture in accordance with ISO 9599. Alternatively, the method specified in annex B may be used to prepare
predried test portions directly from the laboratory sample.
7 Procedure
7.1 Number of determinations
Carry out the determinations at least in duplicate, as far as possible under repeatability conditions, on each test
sample.
NOTE Repeatability conditions exist where mutually independent test results are obtained with the same method on
identical test material in the same laboratory by the same operator using the same equipment within short intervals of time.
7.2 Reagent blank
A reagent blank shall be determined. It is advisable to perform duplicate blank determinations every time an
analysis is carried out on a laboratory sample. The blank samples are carried through the whole procedure, with
the exception that no laboratory sample test portion is required. The average volume of EDTA titrant used for the
reagent blanks is V .
b
7.3 Dissolution
Digest the sample as follows.
Transfer the test portion (6.2) to a 300 ml conical beaker. Moisten the material with about 5 ml of water and add
1 ml of bromine (4.3). Stand for 15 min, swirling the beaker and contents from time to time.
Cautiously add 15 ml of nitric acid (4.4). Place the beaker on a hotplate (5.3) and heat gradually until bromine and
nitrogen oxides are expelled. Add 15 ml of sulfuric acid (4.8). Heat and evaporate the solution until the evolution of
sulfuric acid fumes (approximately 5 ml).
NOTE Care needs to be taken to ensure no loss of material when fuming samples containing significant carbonaceous
material, due to the sample climbing up the walls of the beaker.
Cool and cautiously add about 50 ml of water and heat the solution until boiling. Cool the solution to room
temperature and filter it into a 500 ml conical beaker through a medium-speed cellulose filter paper. Wash the
beaker and filter paper thoroughly with sulfuric acid (4.9). Collect the filtrate and washing solution in the same
beaker.
Reserve the filter paper and acid-insoluble residue for determination of zinc by FAAS (as described in annex C) for
the concentrate being analysed and the analyst performing the test, unless it has been statistically shown, by
previous testing, that the zinc is completely soluble in the initial decomposition. If this step is not routinely
performed, regular checks confirming the validity of its exclusion shall be carried out for each c
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