1、Designation: E 246 01 (Reapproved 2005)Standard Test Methods forDetermination of Iron in Iron Ores and Related Materials byDichromate Titration1This standard is issued under the fixed designation E 246; the number immediately following the designation indicates the year oforiginal adoption or, in th
2、e case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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, a
3、nd 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 AIron by the Hydrogen Sulfide ReductionDichromate Titration Method (30 to 75 % Fe)Test Method BIron by the Stannous Chloride ReductionDichro
4、mate Titration Method (35 to 95 % Fe)Test Method CIron by the Silver Reduction DichromateTitration Method (35 to 95 % Fe)1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-p
5、riate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Section 5 and in special “Warning”paragraphs throughout these test methods.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent Wa
6、terE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE 276 Test Methods for Particle Size or Screen Analysis atNo. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Oresand Related MaterialsE 877 Practice for Sampling and Sample
7、Preparation of IronOres and Related MaterialsE 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory3. Significance and Use3.1 The determination of the total iron content is theprimary means for establishing the commercial value of ironores used in international trade.3
8、.2 These test methods are intended as referee methods forthe determination of iron in iron ores. It is assumed that all whouse these methods will be trained analysts capable of perform-ing common laboratory procedures skillfully and safely. It isexpected that work will be performed in a properly equ
9、ippedlaboratory and that proper waste disposal procedures will befollowed. Appropriate quality control practices must be fol-lowed, such as those described in Guide E 882.4. Apparatus, Reagents, and Instrumental Practices4.1 ApparatusSpecialized apparatus requirements arelisted in the “Apparatus” Se
10、ction 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 Society.3Othergrades may be used provided it is first ascertained that they areof sufficient pur
11、ity to permit their use without adverselyaffecting the expected performance of the determination, asindicated in the “Precision and Bias” Section. Reagent watershall conform to Type II as described in Specification D 1193.5. Hazards5.1 For precautions to be observed in the use of certainreagents and
12、 equipment in this test method refer to PracticesE50.6. Sampling and Sample Preparation6.1 Collect and prepare the test sample in accordance withPractice E 877.6.2 The test sample shall be pulverized to pass a No. 100(150-m) sieve in accordance with Test Method E 276.To1These test methods are under
13、the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and are the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edition approved May 1, 2005. Published June 2005. Originallyapproved in 1
14、964. Last previous edition approved in 2001 as E 246 01.2For 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.3Reag
15、ent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand
16、 National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.facilitate decomposition some ores, such as specular hematite,require grinding to pass a No. 200 (75-m) sie
17、ve.TEST METHOD AIRON BY THE HYDROGENSULFIDE REDUCTION DICHROMATE TITRATIONMETHOD7. Scope7.1 This test method covers the determination of 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 hydrochl
18、oric acid. Theinsoluble residue is removed by filtration, ignited, and treatedfor the recovery of iron, and added to the main solution. To thissolution containing all of the iron, sulfuric acid is added andthe solution evaporated to fumes to expel chlorides. The saltsare dissolved in water, the solu
19、tion heated to boiling, and theiron reduced by a rapid stream of hydrogen sulfide. Theprecipitated sulfides are filtered and washed with an acid-sulfide wash solution until free of iron. The filtrate is thenboiled to expel the hydrogen sulfide, cooled, and titrated withpotassium dichromate solution,
20、 using sodium diphenylaminesulfonate as the indicator.9. Interferences9.1 None of the elements normally found in iron oresinterfere with this test method. These include vanadium,copper, and small amounts of molybdenum, which occasion-ally occur in iron ores.10. Apparatus10.1 Hydrogen Sulfide Generat
21、orHydrogen sulfide shallbe obtained from a cylinder of the compressed gas or from aKipp generator. A consistent flow of 1 L/min shall be main-tained and the gas passed through a water trap to remove anysalts.10.1.1 WarningHydrogen sulfide is extremely toxic. Allprocedures involving its use must be p
22、erformed in an efficientfume hood. Refer to Hazards section in Practices E 50.10.2 Crucibles, platinum, 25-mL capacity.11. Reagents and Materials11.1 Ferrous Ammonium Sulfate Solution (approximately0.10 N)Dissolve 40 g of ferrous ammonium sulfate(FeSO4(NH4)2SO46H2O) in sulfuric acid (1 +19). Transfe
23、r toa 1-L flask and dilute to volume with the same acid. When thesample solution is ready for titration, standardize theFeSO4(NH4)2SO46H2O solution against the standard potas-sium dichromate (0.1000 N), as described in 12.5. Calculate themillilitres of standard potassium dichromate equivalent to 1mL
24、 of the FeSO4(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 to 110C, to a 1-L volumetric flask. Dissolvein water and dilute to 1 L. If prefer
25、red, this solution may beprepared from reagent grade K2Cr2O7, by purifying the salttwice by recrystallizing from water, drying at 110C, pulver-izing in an agate mortar, and drying at 180C to constantweight. The titer of this solution shall be confirmed by meansof standard sample similar in type and
26、composition to the testsample.11.3 Potassium Permanganate Solution (25 g/L)Dissolve25 g of potassium permanganate (KMnO4) in water and diluteto1L.11.4 Sodium Diphenylamine Sulfonate Indicator SolutionDissolve 0.3 g of sodium diphenylamine sulfonate in 100 mLof water. Store in a dark-colored bottle.1
27、1.5 Sodium Pyrosulfate (Na2S2O7).11.6 Sulfuric Acid-Hydrogen Sulfide Wash SolutionAdd20 mL of concentrated sulfuric acid (H2SO4, sp gr 1.84) to 900mL water, cool, dilute to 1 L, and pass a rapid stream of H2Sthrough it for at least 10 min.12. Procedure12.1 Transfer approximately 0.50 g of the test s
28、pecimen toa small weighing bottle previously dried at about 105C. Drythe bottle and contents for1hat105to110C (Note 1). Capthe bottle and cool to room temperature in a desiccator.Momentarily release the cap to equalize the pressure and weighthe capped bottle and sample to the nearest 0.1 mg. Repeat
29、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 analysis.NOTE 1Most ores yield their hygroscopic moisture at this
30、 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 and add 25 mLof HCl. Cover thebeaker and heat, maintaining a
31、temperature below boiling untilmost of the dark particles are dissolved and no further attack isapparent. Add 5 mL of HNO3and digest for another 15 min.Remove from the source of heat, wash the sides and cover ofthe beaker, and dilute to 50 mL with warm water. Filter theinsoluble residue on a fine-te
32、xture paper. Wash the residue withwarm HCl (1 + 50) until the yellow color of ferric chloride isno longer observed and then with warm water six to eighttimes. Collect the filtrate and washings in a 600-mLbeaker andreserve as the main solution (Note 2). Place the paper andresidue in a platinum crucib
33、le. Char the paper at a lowtemperature, then ignite at 950C. Allow the crucible to cool,moisten the residue with H2SO4(1 + 1), add about 5 mLof HF,and heat gently to remove silica and H2SO4(Note 3). Cool thecrucible, add3gofNa2S2O7, and heat until a clear melt isobtained. Cool, place the crucible in
34、 a 250-mL beaker, addabout 25 mL of water and 5 mL of HCl, and warm to dissolvethe melt. Rinse and remove the crucible. Add the solution andwashings to the main solution.NOTE 2If the residue is small in amount and perfectly white, thefiltration, and treatment of the residue may be omitted without ca
35、usingsignificant error.NOTE 3The treatment of the residue depends upon the nature of theminerals present. Many ores require only an H2SO4HF treatment todecompose the residue.E 246 01 (2005)212.3 ReductionTo the combined solution add 10 mL ofH2SO4(1 + 1) and evaporate to copious fumes of SO3(Note 4).
36、Cool, dilute to approximately 100 mL with water, and heat toboiling.Add dropwise KMnO4solution until the permanganatecolor persists. Dilute the solution to 250 mL and again heat toboiling for several minutes. Remove from the source of heatand pass a rapid stream of H2S through the solution for 15 mi
37、n.Warning: Hydrogen sulfide is extremely toxic. All proceduresinvolving its use must be performed in an efficient fume hood.Refer to Hazards section in Practices E 50. Digest at 60C for15 min and filter through a medium-texture paper, collectingthe filtrate in a 500-mLErlenmeyer flask. Wash the prec
38、ipitatedsulfides thoroughly with the H2SO4H2S wash solution. Add10 mL of H2SO4(1 + 1) to the solution in the flask and addglass beads to prevent bumping. Boil for 10 min to expel H2S(lead acetate test paper) and continue boiling for an additional10 min (Note 5). Remove from the source of heat, cover
39、 theflask with a small watch glass, and cool in running water to20C.NOTE 4If the sample contains much calcium, prolonged fuming withH2SO4may lead to the formation of salts that are difficult to dissolve.Therefore, in the presence of considerable calcium, fume just long enoughto expel the chlorides a
40、nd nitrates. Cool, wash the sides of the beaker withwater, and again evaporate to light fumes.NOTE 5If the sample contains an appreciable amount of molybde-num, further precipitation may occur in the filtrate when boiling out theH2S. The effect of residual molybdenum is not significant and may beneg
41、lected.12.4 TitrationAdd to the cooled solution 5 mL of H3PO4and 5 drops of the sodium diphenylamine sulfonate indicatorsolution. Dilute to 350 mL and titrate with the standardK2Cr2O7solution to a distinct purple end point.12.5 Determination of BlankDetermine the blank value ofthe reagents concurren
42、tly 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, accurately measured, of theFeSO4(NH4)2SO46H2O solution. In another beaker place 350mL of cold H2SO4(1 + 9) and add an a
43、ccurately measured 1mL of the FeSO4(NH4)2SO46H2O solution. Add 5 mL ofH3PO4and 5 drops of the sodium diphenylamine sulfonateindicator solution and titrate with the K2Cr2O7solution.Record this titration and subtract from the titration of the blanksolution to obtain the corrected blank.NOTE 6In the ab
44、sence of iron, the diphenylamine sulfonate indicatordoes not react with the K2Cr2O7solution. The addition of theFeSO4(NH4)2SO46H2O is, therefore, necessary to promote indicatorresponse in the blank solution. A correction must be made in terms of itsequivalent in millilitres of K2Cr2O7solution.13. Ca
45、lculation13.1 Calculate the percentage of iron as follows:iron, % 5 A 2 B! 3 C/D 3 100 (1)where:A = millilitres of K2Cr2O7required for titration of thesample,B = millilitres of K2Cr2O7required for titration of theblank,C = iron equivalent of the K2Cr2O7, g/mL, andD = grams of sample used.14. Precisi
46、on and Bias14.1 PrecisionFrom six to nine laboratories analyzed fouriron ore samples to determine iron. The replication made by thedifferent laboratories ranged from 2 to 4, averaging 3 repli-cates. The data was studied by the interlaboratory test proce-dure of Practice E 691-87 modified by weightin
47、g certain sumsto accommodate the unequal replication.4Table 1 shows asummary of these results. From pooled standard deviations, theoverall between-laboratory reproducibility coefficient, R, wascalculated as being 0.38.14.2 The agreement of the determination of iron in the NBSStandard Reference Mater
48、ial with the certified value shows noevidence of bias, well within a 95 % confidence level(R2= 0.24).TEST METHOD BIRON BY THE STANNOUSCHLORIDE REDUCTION DICHROMATETITRATION METHOD15. Scope15.1 This test method covers the determination of total ironin iron ores, concentrates, and agglomerates in the
49、concentra-tion range from 35 to 95 %.16. Summary of Test Method16.1 This test method provides two alternative dissolutionprocedures.16.2 Acid DecompositionThe sample is dissolved in hy-drochloric acid. The insoluble residue is removed by filtration,ignited, treated for the recovery of iron, and added to the mainsolution.4Supporting data giving the results of cooperative testing are available fromASTM International Headquarters. Request RR:E16-63, dated April 23, 1968 withan amendment, dated July 27, 1993.TABLE 1 Precision DataSampl
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