ASTM E508-2008 346 Standard Test Method for Analysis of Calcium and Magnesium in Iron Ores by Flame Atomic Absorption Spectrometry.pdf

1、Designation: E 508 08Standard Test Method forAnalysis of Calcium and Magnesium in Iron Ores by FlameAtomic Absorption Spectrometry1This standard is issued under the fixed designation E 508; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev

2、ision, 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 This test method covers the determination of calciumand magnesium in iron ores, concentrates, and a

3、gglomerates inthe mass fraction (%) range from 0.05 % to 5 % of calcium and0.05 % to 3 % of magnesium.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, i

4、f 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.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE50 Prac

5、tices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 276 Test Method for Particle Size or Screen Analysis atNo. 4 (4.75-mm) Sieve and Finer for M

6、etal-Bearing Oresand Related MaterialsE 663 Practice for Flame Atomic Absorption Analysis3E 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E 135.4. Summary of Test

7、Method4.1 The sample is dissolved in HCl with the addition of asmall amount of HNO3. After evaporation and dehydration,any insoluble residue is filtered, treated for the recovery ofcalcium and magnesium, and added to the main solution. Thesolution is aspirated into the flame of the atomic absorption

8、spectrometer. For calcium, a nitrous oxide-acetylene burner isused, for magnesium, an air-acetylene burner is preferred (Note1). The absorbed energy at the resonance line of the spectrumof calcium or magnesium, or both, is measured by atomicabsorption spectrophotometry and compared with that of thec

9、alibration solutions of the two elements.NOTE 1If a nitrous oxide burner is used for the determination ofmagnesium, the sensitivity is decreased by a factor of about three.If an air-acetylene burner is used for the determination of calcium,several elements, if present in a mass fraction (%) of 1.0 o

10、r greater,interfere with the calcium determination. Also, lanthanum chloride(LaCl3) must be employed and the sensitivity is decreased by a factor ofabout two.5. Significance and Use5.1 This test method is intended as a referee method forcompliance with compositional specifications for impurityconten

11、t. It is assumed that all who use this procedure will betrained analysts capable of performing common laboratorypractices skillfully and safely. It is expected that work will beperformed in a properly equipped laboratory and that properwaste disposal procedures will be followed. Follow appropriatequ

12、ality control practices such as those described in GuideE 882.1This test method is under the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and is the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Mate

13、rials.Current edition approved Dec. 15, 2008. Published January 2009. Originallyapproved in 1973. Last previous edition approved in 2003 as E 508 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStanda

14、rds volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.

15、 Interferences6.1 None of the elements normally found in iron oresinterfere with this test method (Note 1).7. Apparatus7.1 Atomic Absorption Spectrophotometer, meeting the fol-lowing criteria:7.1.1 Minimum SensitivityThe absorbance of the highestcalibration solution (see 8.4) must be at least 0.3.7.

16、1.2 Curve-LinearityThe difference between the read-ings of the highest calibration solutions must be more than 1.4times the difference between the readings for the zero solutionsand the lowest calibration solution.7.1.3 Minimum StabilityThe coefficient of variation of anumber of measurements of the

17、highest calibration solutionand of the zero calibration solution must be less than 1.5 % and0.5 % respectively.NOTE 2Use of digital readout devices or printers, or both, is advis-able.NOTE 3Instrument parameters will vary with each instrument. Thefollowing parameters were successfully used in severa

18、l laboratories andthey can be used as guidelines. In the case of calcium, solutions wereaspirated into a nitrous oxide-acetylene flame of a premix burner. Formagnesium an air-acetylene burner was used.Ca MgHollow cathode lamp, mA 15 15Wavelength, nm 422.7 285.2Nitrous oxide flow rate, L/min 13.8 .Ai

19、r flow rate, L/min . 22Acetylene flow rate, L/min 6.6 4.28. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American

20、Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water sha

21、ll be understood to mean reagent water as definedby Type I of Specification D 1193.8.3 Calcium, Standard Solution (1 mL = 25 g Ca)Dissolve 1.2487 g of anhydrous calcium carbonate (CaCO3)in100 mL of dilute HCl (1 + 3). When solution is complete, cooland dilute to 1 L in a volumetric flask. Transfer 1

22、0 mL of thissolution to a 200-mL volumetric flask. Dilute to volume andmix.8.4 Calcium and Magnesium Calibration SolutionsUsingpipets, transfer, (5.0, 10.0, 20.0, 40.0, and 50.0)-mL portions ofthe standard calcium and magnesium solutions to 200-mLvolumetric flasks (Note 4). Dilute to 90 mL and add 6

23、 mL ofHCl, 60 mL of background solution, and 40 mL of LaCl3solution. Dilute to volume and mix.8.5 Iron, Background Solution (10 g/L)Dissolve 10 g ofhigh-purity iron in 50 mL of HCl, and oxidize by the dropwiseaddition of HNO3. Evaporate to a syrupy consistency. Add20 mL of HCl and dilute to 200 mL w

24、ith water. Add 20 g ofsodium chloride dissolved in 200 mL water and dilute to 1 Lwith water.8.6 Lanthanum Chloride Solution (50 g/L)Dissolve 50 gof LaCl3in 50 mL of HCl and 300 mL of hot water. Cool anddilute to 1 L.8.7 Magnesium, Standard Solution (1 mL = 17.5 g Mg)Dissolve 0.3500 g of high-purity

25、magnesium by slowly adding75 mLof HCl (1 + 3). When dissolved, dilute with water to 1 Lin a volumetric flask. Transfer 10 mL of this solution to a200-mL volumetric flask, dilute to volume, and mix.8.8 Zero Calibration SolutionTransfer 60 mL of the back-ground solution to a 200-mL volumetric flask, a

26、dd 6 mL ofHCl, 40 mL of LaCl3solution, dilute to volume, and mix.NOTE 4The range of calcium or magnesium that can be covered mayvary from instrument to instrument. Attention should be paid to theminimum criteria given in 7.1.9. Hazards9.1 For precautions to be observed in this method, refer toPracti

27、ces E50.10. Sample Preparation10.1 The analytical sample shall be pulverized to pass a150-m sieve (see Test Method E 276).NOTE 5To facilitate decomposition, some ores, such as specularhematite, require grinding to pass a 75-m sieve.11. Procedure11.1 Transfer approximately 1.0 g of the sample to a sm

28、allweighing bottle previously dried at about 150 C. Dry thebottle and contents for 1 h at 105 C to 110 C. Cap the bottleand cool to room temperature in a desiccator. Momentarilyrelease the cap to equalize the pressure and weigh the cappedbottle and sample to the nearest 0.1 mg. Repeat the drying and

29、weighing until there is no further weight loss. Transfer thesample to a 250-mL beaker and reweigh the capped bottle tothe nearest 0.1 mg. The difference between the two weights isthe weight of the sample taken for analysis.11.2 Carry a reagent blank through all steps of the procedurestarting with 11

30、.3.11.3 Decomposition of SampleMoisten the sample with afew milliliters of water, add 25 mL of HCl, cover, and digestbelow the boiling point until no further attack is apparent. Add2 mL of HNO3and digest for several minutes. Remove thecover and evaporate the solution to dryness. Heat the salts ona h

31、ot plate at 105 C to 110 C for 15 min. Add 5 mL of HCl,cover the beaker, and warm for several minutes. Add 50 mL ofwater and warm until soluble salts are in solution. Filter on afine-textured paper, and collect the filtrate in a 250-mL beaker.Transfer the residue quantitatively to the filter paper.

32、Washalternately three times with hot HCl (1 + 9) and hot water until4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC, http:/www.chemistry.org. For suggestions onthe testing of reagents not listed by the American Chemical Society, see AnnualStanda

33、rds for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., http:/, and the United States Pharmacopeia and National Formulary, U.S.Pharmacopeial Convention, Inc. (USPC), Rockville, MD, http:/www.usp.org.E508082the yellow color of ferric chloride is no longer apparent.Transfer the paper and residue

34、to a platinum crucible. Reservethe filtrate.11.4 Treatment of ResidueIgnite the paper and residue inthe platinum crucible. Cool, moisten with several drops ofwater, add three or four drops of dilute H2SO4(1 + 1) and10 mL of HF. Evaporate slowly to expel silica and then fumeoff the excess of H2SO4. F

35、inally ignite at about 700 C. Add1 g of anhydrous sodium carbonate to the residue, cover thecrucible, and fuse over a burner or in a muffle furnace until aclear melt is obtained. Dissolve the cool melt in the reservedfiltrate from 11.3, remove and wash the crucible and cover.Transfer the solution to

36、 a 200-mL volumetric flask, dilute tovolume, and mix. If the solution is cloudy at this stage,indicating the presence of titania, filter a portion of the solutionthrough a dry paper into a dry beaker. Transfer a proper aliquotof this solution (see Table 1) to a 200-mL volumetric flask andadd 40 mL o

37、f the LaCl3solution. Add the amount of back-ground solution and HCl indicated in Table 1, dilute to volume,and mix.NOTE 6Dilutions shown in Table 1 will provide concentrations ofcalcium and magnesium falling within the range of the calibrationsolutions.11.5 Adjustment of Atomic AbsorptionSpectrophot

38、ometerIn accordance with Practice E 663, set theinitial instrument parameters to the values in Note 3. Light theburner and aspirate water until the instrument comes to thermalequilibrium. Optimize instrument response by adjusting thewavelength, fuel, air, burner, and nebulizer while aspirating thehi

39、ghest calibration solution to obtain maximum absorption orabsorbance.Aspirate water until a steady signal is obtained andadjust the instrument readout system to obtain zero absorptionor absorbance.NOTE 7The manufacturers instructions for igniting and extinguish-ing the nitrous oxide-acetylene burner

40、 should be strictly followed to avoidpossible explosion hazards. Tinted safety glasses should be worn by theoperator whenever the flame is burning.11.6 MeasurementsAspirate water until the initial readingis again obtained.Aspirate the calibration solutions in the orderof increasing absorption or abs

41、orbance starting with the zerocalibration solution. When a stable response is obtained foreach solution, record the readings.Aspirate the test solutions atthe proper points in the calibration series. Aspirate waterbetween each calibration and test solution. Repeat all measure-ments at least two more

42、 times.12. Calculation12.1 Only if necessary, convert the average of the readingsfor each calibration solution to absorbance. Obtain the netabsorbance of each calibration solution by subtracting theaverage absorbance of the zero calibration solution. In a similarmanner, obtain the net absorbance of

43、the test solution bysubtracting the absorbance of the reagent blank solution.12.2 Prepare calibration curves for calcium and magnesiumby plotting the net absorbance values of the calibrationsolutions against micrograms of calcium or magnesium permillilitre.12.3 Convert the net absorbance values of t

44、he samplesolution to micrograms of calcium and magnesium per millili-tre by means of the calibration curves.12.4 Calculate the mass fraction (%) of calcium and mag-nesium as follows:Calcium or magnesium, % 5 A 3 200!/B 3 10 000! (1)where:A = calcium or magnesium per mL, g, andB = sample represented

45、in the 200-mL volume of the finaltest solution, g.13. Precision and Bias513.1 PrecisionTable 2 indicates the precision of the testmethod within and between laboratories when applied to anumber of samples of iron ore.13.2 BiasNo information on the accuracy of this testmethod is known. The accuracy of

46、 this test method may bejudged by comparison of accepted values for certified referencematerials with the mean determined through interlaboratorytesting.14. Keywords14.1 atomic absorption spectroscopy; calcium; iron ores;magnesium5Supporting data giving the results of cooperative testing have been f

47、iled atASTM International Headquarters. Request RR:E16-1001.TABLE 1 Dilution Guide for Test SolutionElementExpected Percentage ofElement in SampleAliquot, mLEquivalent Weight ofSample, gBackground Solution toBe Added, mLHydrochloric AcidAdded, mLCalcium 0.05 to 0.5 50 0.25 45 4Calcium 0.5 to 2.5 10

48、0.05 60 6Calcium 2.5 to 10.0 2 0.01 60 6Magnesium 0.05 to 0.25 40 0.20 50 4Magnesium 0.25 to 1.25 10 0.05 60 6Magnesium 1.25 to 5.00 2 0.01 60 6E508083ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Use

49、rs of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will recei