1、Designation: E 508 03Standard Test Method forCalcium and Magnesium in Iron Ores by Atomic AbsorptionSpectrometry1This 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 revision, the year of
2、 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 This test method covers the determination of calciumand magnesium in iron ores, concentrates, and agglomerates inthe
3、 concentration range from 0.05 to 5 % of calcium and 0.05to 3 % of magnesium.1.2 This standard does not purport to address all of thesafety problems, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determ
4、ine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE50 Practices for Apparatus, Reagents, and Safety Precau-tions for Chemical Analysis of MetalsE 135 Terminology Relating to Analytical Chemistry forMetals, O
5、res and Related MaterialsE 276 Test Method for Particle Size or Screen Analysis atNo. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Oresand Related MaterialsE 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory2.2 Other DocumentsE 663-86 (1991) Practice for Flame Atom
6、ic AbsorptionAnalysis33. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E 135.4. Summary of Test Method4.1 The sample is dissolved in hydrochloric acid with theaddition of a small amount of nitric acid.After evaporation anddehydration, any insoluble
7、residue is filtered, treated for therecovery of calcium and magnesium, and added to the mainsolution. The solution is aspirated into the flame of the atomicabsorption spectrometer. For calcium, a nitrous oxide-acetylene burner is used, for magnesium, an air-acetyleneburner is preferred (Note 1). The
8、 absorbed energy at theresonance line of the spectrum of calcium or magnesium, orboth, is measured by atomic absorption spectrophotometry andcompared with that of the calibration solutions of the twoelements.NOTE 1If a nitrous oxide burner is used for the determination ofmagnesium, the sensitivity i
9、s decreased by a factor of about three.If an air-acetylene burner is used for the determination of calcium,several elements, if present in percent amounts, interfere with the calciumdetermination. Also, lanthanum chloride must be employed and thesensitivity is decreased by a factor of about two.5. S
10、ignificance and Use5.1 This test method is intended as a referee method forcompliance with compositional specifications for impuritycontent. It is assumed that all who use this procedure will betrained analysts capable of performing common laboratorypractices skillfully and safely. It is expected th
11、at work will beperformed in a properly equipped laboratory and that properwaste disposal procedures will be followed. Follow appropriatequality control practices such as those described in GuideE 882.6. Interferences6.1 None of the elements normally found in iron oresinterfere with this test method
12、(Note 1).1This test method is under the jurisdiction of ASTM Committee E-1 onAnalytical Chemistry for Metals, Ores, and Related Materials and is the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edition approved June 10, 2003. Publish
13、ed August 2003. Originallyapproved in 1973. Last previous edition approved in 1998 as E 508 98.2For 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 Documen
14、t Summary page onthe ASTM website.3Available from Global Engineering Documents, 15 Inverness Way, EastEnglewood, CO 80112-57041Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 Atomic Absorption Spectrophotometer, meetin
15、g the fol-lowing criteria:7.1.1 Minimum SensitivityThe absorbance of the highestcalibration solution (see 8.4) must be at least 0.3.7.1.2 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 ze
16、ro solutionsand the lowest calibration solution.7.1.3 Minimum StabilityThe coefficient of variation of anumber of measurements of the highest calibration solutionand of the zero calibration solution must be less than 1.5 % and0.5 % respectively, relative to the measurement of the highestcalibration
17、solution.NOTE 2Use of a strip chart recorder or digital readout device, or both,is advisable.NOTE 3Instrument parameters will vary with each instrument. Thefollowing parameters were successfully used in several laboratories andthey can be used as guidelines. In the case of calcium, solutions wereasp
18、irated into a nitrous oxide-acetylene flame of a premix burner. Formagnesium an air-acetylene burner was used.Ca MgHollow cathode lamp, mA 15 15Wavelength, l, 4227 2852Nitrous oxide flow rate, L/min 13.8 .Air flow rate, L/min . 22Acetylene flow rate, L/min 6.6 4.28. Reagents and Materials8.1 Purity
19、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 Chemical Society wheresuch specifications are available4. Other grades may be used,provided i
20、t 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 shall be understood to mean reagent water as definedby Type I of Specification D 1193.8.3 Calci
21、um, Standard Solution (1 mL = 25 g Ca)Dissolve 1.2487 g of anhydrous calcium carbonate in 100 mLof dilute hydrochloric acid (HCl) (1+3). When solution iscomplete, cool and dilute to 1 L in a volumetric flask. Transfer10 mL of this solution to a 200-mL volumetric flask. Dilute tovolume, and mix.8.4 C
22、alcium 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, add 6 mL of HCl(sp gr 1.19), 60 mL of background solution, and 40 mL oflanthanum ch loride
23、 solution. Dilute to volume, and mix.8.5 Iron, Background Solution (10 g/L)Dissolve 10 g ofhigh-purity iron in 50 mL of HCl, (sp gr 1.19) and oxidize bythe dropwise addition of nitric acid (HNO3, sp gr 1.42).Evaporate to a syrupy consistency. Add 20 mL of HCl (sp gr1.19) and dilute to 200 mL with wa
24、ter. Add 20 g of sodiumchloride (NaCl) dissolved in 200 mL water and dilute to 1 Lwith water.8.6 Lanthanum Chloride Solution (50 g/L)Dissolve 50 gof lanthanum chloride in 50 mL of HCl (sp gr 1.19) and 300mL of hot water. Cool and dilute to 1 L.8.7 Magnesium, Standard Solution (1 mL = 17.5 g Mg)Disso
25、lve 0.3500 g of high-purity magnesium by slowly adding75 mL of 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 thebackground solution to a 2
26、00-mLvolumetric flask, add 6 mLofHCl (sp gr 1.19), 40 mL of lanthanum chloride solution, diluteto 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 precauti
27、ons to be observed in this method, refer toPractice E 50.10. Sample Preparation10.1 The analytical sample shall be pulverized to pass a No.100 (150-m) sieve (see Test Method E 276).NOTE 5To facilitate decomposition, some ores, such as specularhematite, require grinding to pass a No. 200 (75-m) sieve
28、.Table 111. Procedure11.1 Transfer approximately 1.0 g of the sample to a smallweighing bottle previously dried at about 150C. Dry the bottleand contents for1hat105to110C. Cap the bottle and coolto room temperature in a desiccator. Momentarily release thecap to equalize the pressure and weigh the ca
29、pped bottle andsample to the nearest 0.1 mg. Repeat the drying and weighinguntil there is no further weight loss. Transfer the sample to a250-mLbeaker and reweigh the capped bottle to the nearest 0.1mg. The difference between the two weights is the weight ofthe sample taken for analysis.11.2 Carry a
30、 reagent blank through all steps of the procedurestarting with 11.3.11.3 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. Add2mLofHNO3and digest for several minutes. Remove thecov
31、er and evaporate the solution to dryness. Heat the salts ona hot plate at 105 to 110C for 15 min.Add 5 mL of HCl, coverthe beaker, and warm for several minutes. Add 50 mL of waterand warm until soluble salts are in solution. Filter on afine-textured paper, and collect the filtrate in a 250-mL beaker
32、.Transfer the residue quantitatively to the filter paper. Washalternately three times with hot HCl (1+9) and hot water untilthe yellow color of ferric chloride is no longer apparent.Transfer the paper and residue to a platinum crucible. Reservethe filtrate.4Reagent Chemicals, American Chemical Socie
33、ty Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeia
34、l Convention, Inc. (USPC), Rockville,MD.E50803211.4 Treatment of ResidueIgnite the paper and residue inthe platinum crucible. Cool, moisten with several drops ofwater, add 3 or 4 drops of dilute sulfuric acid (H2SO4, 1+1) and10 mL of hydrofluoric acid (HF). Evaporate slowly to expelsilica and then f
35、ume off the excess of H2SO4. Finally ignite atabout 700C. Add1gofanhydrous sodium carbonate(Na2CO3) to the residue, cover the crucible, and fuse over aburner or in a muffle furnace until a clear melt is obtained.Dissolve the cool melt in the reserved filtrate from 11.3,remove and wash the crucible a
36、nd cover. Transfer the solutionto a 200-mL volumetric flask, dilute to volume, and mix. If thesolution is cloudy at this stage, indicating the presence oftitania, filter a portion of the solution through a dry paper intoa dry beaker. Transfer a proper aliquot of this solution (seeTable 1) to a 200-m
37、L volumetric flask and add 40 mL of thelanthanum chloride solution. Add the amount of backgroundsolution and HCl indicated in Table 1, dilute to volume, andmix.NOTE 6Dilutions shown in Table 1 will provide concentrations ofcalcium and magnesium falling within the range of the calibrationsolutions.11
38、.5 Adjustment of Atomic AbsorptionSpectrophotometerIn accordance with Practice E 663 (dis-continued 1997), set the initial instrument parameters to thevalues in Note 3. Light the burner and aspirate water until theinstrument comes to thermal equilibrium. Optimize instrumentresponse by adjusting the
39、wavelength, fuel, air, burner, andnebulizer while aspirating the highest calibration solution toobtain maximum absorption or absorbance. Aspirate wateruntil a steady signal is obtained and adjust the instrumentreadout system to obtain zero absorption or absorbance.NOTE 7The manufacturers instruction
40、s for igniting and extinguish-ing the nitrous oxide-acetylene burner 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 t
41、he calibration solutions in the orderof increasing absorption or absorbance 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 calib
42、ration and test solution. Repeat all measure-ments at least two more 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 cal
43、ibration solution. In a similarmanner, obtain the net absorbance of 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
44、 magnesium permillilitre.12.3 Convert the net absorbance values of the samplesolution to micrograms of calcium and magnesium per millili-tre by means of the calibration curves.12.4 Calculate the percentage of calcium and magnesium asfollows:Calcium or magnesium, % 5 A 3 200!/B 3 10 000! (1)where:A =
45、 calcium or magnesium per mL, g, andB = sample represented 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 o
46、n the accuracy of this testmethod is known. The accuracy of this test method may bejudged by comparison of accepted values for standard refer-ence materials with the mean determined through interlabora-tory testing.14. Keywords14.1 atomic absorption spectroscopy; calcium; iron ores;magnesium5Support
47、ing data giving the results of cooperative testing have been filed atASTM International Headquarters. Request RR E161001.TABLE 1 Dilution Guide for Test SolutionElementExpected Percentage of Elementin SampleAliquot, mLEquivalent Weight ofSample, gBackground Solution toBe Added, mLHydrochloric AcidAd
48、ded, mLCalcium 0.05 to 0.5 50 0.25 45 4Calcium 0.5 to 2.5 10 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 6E508033ASTM International takes no position respecting the validity of any patent rights assert
49、ed in connection with any item mentionedin this standard. Users 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 Inte
