1、Designation: E246 10 (Reapproved 2015)Standard Test Methods forDetermination of Iron in Iron Ores and Related Materials byDichromate Titrimetry1This standard is issued under the fixed designation E246; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the determination of total ironin iron ores, concentrates, and
3、 agglomerates in the concentra-tion range 30 % to 95 % iron.1.2 The test methods in this standard are contained in thesections indicated as follows:Test Method A Iron by the Hydrogen Sulfide Reduction DichromateTitration Method (30 % to 75 % Fe)Test Method BIron by the Stannous Chloride Reduction Di
4、chromateTitration Method (35 % to 95 % Fe)Test Method CIron by the Silver Reduction Dichromate TitrationMethod (35 % to 95 % Fe)1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purport to address al
5、l of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Section 5 and in speci
6、al “Warning”paragraphs throughout these test methods.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE276 Test Method for Particle Size or Scre
7、enAnalysis at No.4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores andRelated MaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE877 Practice for Sampling and Sample Preparation of IronOres and Related Materials for Determination of Chemi-cal C
8、omposition and Physical PropertiesE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1028 Test Method for Total Iron in Iron Ores and RelatedMaterials by Dichromate Titrimetry (Withdrawn 2003)33. Significance and Use3.1 The determination of the total iron content is
9、 theprimary means for establishing the commercial value of ironores used in international trade.3.2 These test methods are intended as referee methods forthe determination of iron in iron ores. It is assumed that all whouse these test methods will be trained analysts capable ofperforming common labo
10、ratory procedures skillfully andsafely. It is expected that work will be performed in a properlyequipped laboratory and that proper waste disposal procedureswill be followed.Appropriate quality control practices must befollowed, such as those described in Guide E882.4. Apparatus, Reagents, and Instr
11、umental Practices4.1 ApparatusSpecialized apparatus requirements arelisted in the “Apparatus” Section in each test method.4.2 Reagents:4.2.1 Purity of ReagentsUnless otherwise indicated, allreagents used in these test methods shall conform to the reagentgrade specifications of the American Chemical
12、Society.4Othergrades may be used provided it is first ascertained that they areof sufficient purity to permit their use without adverselyaffecting the expected performance of the determination, as1These test methods are under the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals,
13、Ores, and Related Materials and are the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edition approved Aug. 15, 2015. Published August 2015. Originallyapproved in 1964. Last previous edition approved in 2010 as E246 10. DOI:10.1520/E0
14、246-10R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical stand
15、ard is referenced onwww.astm.org.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC, www.chemistry.org. For suggestions on thetesting of reagents not listed by the American Chemical Society, see the UnitedStates Pharmacopeia and National Formulary,
16、 U.S. Pharmacopeial Convention,Inc. (USPC), Rockville, MD, http:/www.usp.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1indicated in the “Precision and Bias” Section. Reagent watershall conform to Type II as described in Specific
17、ation D1193.5. Hazards5.1 For precautions to be observed in the use of certainreagents and equipment in this test method refer to PracticesE50.6. Sampling and Sample Preparation6.1 Collect and prepare the test sample in accordance withPractice E877.6.2 The test sample shall be pulverized to pass a N
18、o. 100(150-m) sieve in accordance with Test Method E276.Tofacilitate decomposition some ores, such as specular hematite,require grinding to pass a No. 200 (75-m) sieve.TEST METHOD AIRON BY THE HYDROGENSULFIDE REDUCTION DICHROMATE TITRATIONMETHOD7. Scope7.1 This test method covers the determination o
19、f total ironin iron ores, concentrates, and agglomerates in the concentra-tion range from 30 % to 75 %.8. Summary of Test Method8.1 The sample is dissolved in HCl. The insoluble residue isremoved by filtration, ignited, treated for the recovery of iron,and added to the main solution. To this solutio
20、n containing allof the iron, H2SO4is added and the solution evaporated tofumes to expel chlorides. The salts are dissolved in water, thesolution heated to boiling, and the iron reduced by a rapidstream of hydrogen sulfide (H2S). The precipitated sulfides arefiltered and washed with an acid-sulfide w
21、ash solution untilfree of iron. The filtrate is then boiled to expel the H2S, cooled,and titrated with K2Cr2O7solution, using sodium diphenylam-ine sulfonate as the indicator.9. Interferences9.1 None of the elements normally found in iron oresinterfere with this test method. These include vanadium,c
22、opper, and small amounts of molybdenum, which occasion-ally occur in iron ores.10. Apparatus10.1 Hydrogen Sulfide GeneratorH2S shall be obtainedfrom a cylinder of the compressed gas or from a Kippgenerator. A consistent flow of 1 Lmin shall be maintainedand the gas passed through a water trap to rem
23、ove any salts.10.1.1 WarningH2S is extremely toxic. All proceduresinvolving its use must be performed in an efficient fume hood.Refer to Hazards section in Practices E50.10.2 Crucibles, platinum, 25-mL capacity.11. Reagents and Materials11.1 Ferrous Ammonium Sulfate Solution (approximately0.10 N) Di
24、ssolve 40 g of ferrous ammonium sulfate(FeSO4(NH4)2SO46H2O) in H2SO4(1 + 19). Transfer to a1-L flask and dilute to volume with the same acid. When thesample solution is ready for titration, standardize theFeSO4(NH4)2SO46H2O solution against the standardK2Cr2O7(0.1000 N), as described in 12.5. Calcul
25、ate themillilitres of standard K2Cr2O7equivalent to 1 mL of theFeSO4(NH4)2SO46H2O solution.11.2 Potassium Dichromate, Standard Solution (0.1000N)Transfer 4.9031 g of primary standard grade potassiumdichromate (K2Cr2O7); previously ground in an agate mortar,and dried at 105 C to 110 C, to a 1-L volum
26、etric flask.Dissolve in water and dilute to 1 L. If preferred, this solutionmay be prepared from reagent grade K2Cr2O7, by purifying thesalt twice by recrystallizing from water, drying at 110 C,pulverizing in an agate mortar, and drying at 180 C to constantweight. The titer of this solution shall be
27、 confirmed by meansof standard sample similar in type and composition to the testsample.11.3 Potassium Permanganate Solution (25 gL)Dissolve25 g of potassium permanganate (KMnO4) in water and diluteto 1 L.11.4 Sodium Diphenylamine Sulfonate Indicator SolutionDissolve 0.3 g of sodium diphenylamine su
28、lfonate in 100 mLof water. Store in a dark-colored bottle.11.5 Sodium Pyrosulfate (Na2S2O7).11.6 Sulfuric Acid-Hydrogen Sulfide Wash SolutionAdd20 mL of concentrated H2SO4(H2SO4, sp gr 1.84) to 900 mLwater, cool, dilute to 1 L, and pass a rapid stream of H2Sthrough it for at least 10 min.12. Procedu
29、re12.1 Transfer approximately 0.50 g of the test specimen to asmall weighing bottle previously dried at about 105 C. Drythe bottle and contents for 1 h at 105 C to 110 C (Note 1).Cap the bottle and cool to room temperature in a desiccator.Momentarily release the cap to equalize the pressure and weig
30、hthe capped bottle and sample to the nearest 0.1 mg. Repeat thedrying and weighing until there is no further weight loss.Transfer the test specimen to a 250-mL beaker and reweigh thecapped bottle to the nearest 0.1 mg. The difference between thetwo weights is the weight of the sample taken for analy
31、sis.NOTE 1Most ores yield their hygroscopic moisture at this tempera-ture. If a drying temperature other than that specified is required, this shallbe determined by mutual agreement between manufacturer and purchaser.12.2 Decomposition of the SampleMoisten the samplewith a few millilitres of water a
32、nd add 25 mL of HCl. Coverthe beaker and heat, maintaining a temperature below boilinguntil most of the dark particles are dissolved and no furtherattack is apparent. Add 5 mL of HNO3and digest for another15 min. Remove from the source of heat, wash the sides andcover of the beaker, and dilute to 50
33、 mL with warm water.Filter the insoluble residue on a fine-texture paper. Wash theresidue with warm HCl (1 + 50) until the yellow color of ferricchloride is no longer observed and then with warm water sixtimes to eight times. Collect the filtrate and washings in a600-mLbeaker and reserve as the main
34、 solution (Note 2). Placethe paper and residue in a platinum crucible. Char the paper atE246 10 (2015)2a low temperature, then ignite at 950 C. Allow the crucible tocool, moisten the residue with H2SO4(1 + 1), add about 5 mLof HF, and heat gently to remove silica and H2SO4(Note 3).Cool the crucible,
35、 add 3 g of Na2S2O7, and heat until a clearmelt is obtained. Cool, place the crucible in a 250-mL beaker,add about 25 mL of water and 5 mL of HCl, and warm todissolve the melt. Rinse and remove the crucible. Add thesolution and washings to the main solution.NOTE 2If the residue is small in amount an
36、d perfectly white, thefiltration, and treatment of the residue may be omitted without causingsignificant error.NOTE 3The treatment of the residue depends upon the nature of theminerals present. Many ores require only an H2SO4HF treatment todecompose the residue.12.3 ReductionTo the combined solution
37、 add 10 mL ofH2SO4(1 + 1) and evaporate to copious fumes of sulfurtrioxide (SO3)(Note 4). Cool, dilute to approximately 100 mLwith water, and heat to boiling.Add dropwise KMnO4solutionuntil the permanganate color persists. Dilute the solution to250 mL and again heat to boiling for several minutes. R
38、emovefrom the source of heat and pass a rapid stream of H2S throughthe solution for 15 min. (WarningHydrogen sulfide isextremely toxic. All procedures involving its use must beperformed in an efficient fume hood. Refer to Hazards sectionin Practices E50.) Digest at 60 C for 15 min and filter through
39、a medium-texture paper, collecting the filtrate in a 500-mLErlenmeyer flask. Wash the precipitated sulfides thoroughlywith the H2SO4H2S wash solution. Add 10 mL of H2SO4(1 + 1) to the solution in the flask and add glass beads toprevent bumping. Boil for 10 min to expel H2S (lead acetatetest paper) a
40、nd continue boiling for an additional 10 min (Note5). Remove from the source of heat, cover the flask with asmall watch glass, and cool in running water to 20 C.NOTE 4If the sample contains much calcium, prolonged fuming withH2SO4may lead to the formation of salts that are difficult to dissolve.Ther
41、efore, in the presence of considerable calcium, fume just long enoughto expel the chlorides and nitrates. Cool, wash the sides of the beaker withwater, and again evaporate to light fumes.NOTE 5If the sample contains an appreciable amount of molybdenum,further precipitation may occur in the filtrate
42、when boiling out the H2S.The effect of residual molybdenum is not significant and may beneglected.12.4 TitrationAdd to the cooled solution 5 mL of phos-phoric acid (H3PO4) and five drops of the sodium diphenylam-ine sulfonate indicator solution. Dilute to 350 mL and titratewith the standard K2Cr2O7s
43、olution to a distinct purpleendpoint.12.5 Determination of BlankDetermine the blank value ofthe reagents concurrently with the test determination, using thesame amount of all reagents and following all the steps of theprocedure. Immediately before titrating with the K2Cr2O7solution, add 1.0 mL, accu
44、rately measured, of theFeSO4(NH4)2SO46H2O solution. In another beaker place350 mLof cold H2SO4(1 + 9) and add an accurately measured1 mL of the FeSO4(NH4)2SO46H2O solution. Add 5 mL ofH3PO4and five drops of the sodium diphenylamine sulfonateindicator solution and titrate with the K2Cr2O7solution.Rec
45、ord this titration and subtract from the titration of the blanksolution to obtain the corrected blank.NOTE 6In the absence of iron, the diphenylamine sulfonate indicatordoes not react with the K2Cr2O7solution. The addition of theFeSO4(NH4)2SO46H2O is, therefore, necessary to promote indicatorrespons
46、e in the blank solution. A correction must be made in terms of itsequivalent in millilitres of K2Cr2O7solution.13. Calculation13.1 Calculate the percentage of iron as follows:iron, % 5 A 2 B! 3 C/D# 3100 (1)where:A = millilitres of K2Cr2O7required for titration of thesample,B = millilitres of K2Cr2O
47、7required for titration of theblank,C = iron equivalent of the K2Cr2O7, g/mL, andD = grams of sample used.14. Precision and Bias14.1 PrecisionFrom six to nine laboratories analyzed fouriron ore samples to determine iron. The replication made by thedifferent laboratories ranged from two to four, aver
48、aging threereplicates. The data was studied by the interlaboratory testprocedure of Practice E691 87 modified by weighting certainsums to accommodate the unequal replication.5Table 1 showsa summary of these results. From pooled standard deviations,the overall between-laboratory reproducibility coeff
49、icient, R,was calculated as being 0.38.5Supporting data giving the results of cooperative testing have been filed atASTM International Headquarters and may be obtained by requesting ResearchReport RR:E16-63, dated April 23, 1968, with an amendment, dated July 27, 1993.TABLE 1 Precision DataSampleNumber ofLaboratoriesIron Found%Repeatability ReproducibilitysrRI(2.8 sr)sRR2(2.8 sR)Seine River Ore 9 57.52 0.125 0.35 0.126 0.35Knob Lake Ore 9 58.45 0.097 0.27 0.136 0.38NBS 27d (64.96 % Fe) 6 65.01 0.057 0.16 0.085 0.24Chilean Iro
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