1、Designation: E815 11Standard Test Method forDetermination of Calcium Fluoride in Fluorspar byComplexometric Titrimetry1This standard is issued under the fixed designation E815; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the ye
2、ar 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 calciumfluoride in acid-grade fluorspar and other types of fluorspa
3、r thatcan be rendered soluble by the procedure described in the testmethod.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 test method has been evaluated in accordance withPractice E1601 and Guide E1763. Unless othe
4、rwise noted inthe precision and bias section, the lower limit in the scope ofeach method specifies the lowest analyte content that may beanalyzed with acceptable error (defined as a nominal 5 % riskof obtaining a 50 % or larger relative difference in results onthe same test sample in two laboratorie
5、s).1.4 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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Reference
6、d Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE276 Test Method fo
7、r Particle Size or Screen Analysis atNo. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Oresand Related MaterialsE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Metho
8、dE1763 Guide for Interpretation and Use of Results fromInterlaboratory Testing of Chemical Analysis Methods3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E135.4. Summary of Test Method4.1 The sample is decomposed by digesting with nitric andperchl
9、oric acids and the fluorine is expelled by fuming. Theresidue is dissolved in dilute hydrochloric acid, the solutionmade alkaline, and the calcium titrated with standard EDTAsolution. Calcium present as carbonate is determined in aseparate sample with EDTA solution, after extracting theformer with d
10、ilute acetic acid. A correction for calciumfluoride, solubilized by dilute acetic acid digestion, is applied,by determining the fluoride in the acetic acid extract by fluorideion-selective electrode. The CaF2content is then calculated.5. Significance and Use5.1 Fluorspar is used as a flux in steelma
11、king, glass industry,and manufacture of hydrofluoric acid.5.2 This test method is intended to be used for compliancewith compositional specifications for calcium fluoride content.It is assumed that all who use these procedures will be trainedanalysts capable of performing common laboratory procedure
12、sskillfully and safely. It is expected that work will be performedin a properly equipped laboratory and that proper wastedisposal procedures will be followed. Appropriate qualitycontrol practices must be followed such as those described inGuide E882.6. Interferences6.1 None of the elements normally
13、found in fluorsparinterfere with this test method.7. Apparatus7.1 Fluoride Ion-Selective Electrode.31This 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, Concent
14、rates, and Related Metal-lurgical Materials.Current edition approved Sept. 1, 2011. Published September 2011. Originallyapproved in 1981. Last previous edition approved in 2004 as E815 04. DOI:10.1520/E0815-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Custo
15、mer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Thermo Scientific Orion model 94-91 has been found suitable for this purpose.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West C
16、onshohocken, PA 19428-2959, United States.7.2 Magnetic Stirrer and TFE-Fluorocarbon-Coated SpinBar.7.3 pH Meter with High ImpedanceSuitable for ion-selective electrode.7.4 Polyethylene Beakers, 100-mL.7.5 Single Junction Ag/AgCl Reference Electrode.48. Reagents and Materials8.1 Purity of ReagentsRea
17、gent 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 available.5Other grades may be used,provided it is first asce
18、rtained that the reagent is of sufficienthigh 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 conformingto Type I or II of Specification D1193. Type III or IV may b
19、eused if they effect no measurable change in the blank orsample.8.3 Acetic Acid Solution (1 + 10)Mix 1 volume of glacialacetic acid (CH3COOH) with 10 volumes of water.8.4 Calcium Carbonate, high purity (minimum 99.95 %CaCO3).8.5 Ethylenediaminetetraacetic Acid Disodium Salt(EDTA)-Na2C10H14O8N22H2O S
20、olution (0.025 mol/L)Dissolve 9.3062 g of EDTA in water, transfer to a 1-Lvolumetric flask, dilute to volume, and mix.8.6 Hydroxynaphthol Blue Indicator Grind 0.2 g of thesalt with 50 g sodium chloride (NaCl).8.7 Potassium Acetate BufferDilute 283 mL of glacialacetic acid (CH3COOH) to 1200 mLwith wa
21、ter. While coolingand stirring, add potassium hydroxide solution B (KOH) (8.9)to adjust the pH to 5.0 (approximately 350 mL of KOHsolution B are required).8.8 Potassium Hydroxide Solution ADissolve 225 g ofpotassium hydroxide (KOH) in water and dilute to 1 L withwater. Store in a plastic bottle.8.9
22、Potassium Hydroxide Solution BDissolve 500 g ofpotassium hydroxide (KOH) in water and dilute to 1 L. Storein a plastic bottle.8.10 Sodium Fluoride SolutionDissolve 0.2210 g sodiumfluoride (NaF) in water in a polyethylene beaker and dilute to1 L in a volumetric flask. Store in a stoppered polyethylen
23、ebottle. This solution has a concentration of 1 mL = 0.10 mg Fand is stable for 6 months.8.11 Triethanolamine Solution (1 + 1)Mix 50 mL of tri-ethanolamine (NC6H15O3) with 50 mL of water.9. Hazards9.1 For precautions to be observed in this method, refer toPractice E50.10. Sampling, Test Specimens, a
24、nd Test Units10.1 Pulverize the test units so that 95 % passes a No. 100mesh sieve (150-m) in accordance with Test Methods E276.11. Calibration and Standardization11.1 StandardizationWeigh and transfer 2.4970 g ofCaCO3(dried at 110 C for 1 h and cooled in a desiccator) to a600-mL beaker. Using a hoo
25、d and appropriate personal protec-tive equipment, cautiously add 75 mL of HCl and warm. Cool,transfer to a 1-L volumetric flask, dilute to volume with water,and mix. This solution has a concentration of 1 mL = 1.0000mg of calcium.11.1.1 Titration:11.1.1.1 Transfer a 50.00-mL aliquot of this solution
26、 to a400-mL beaker, add 5 mL of triethanolamine (8.11), dilute to200 mL, make just alkaline with potassium hydroxide solutionA(8.8), using a strip of litmus paper, and then add an additional15 mL of potassium hydroxide solution A (8.8).11.1.1.2 Add 0.2 g of hydroxynaphthol blue indicator andtitrate
27、immediately with 0.025 M EDTA solution ( 8.5). At theequivalence point, the color changes from pink to blue.Determine the calcium equivalent of the EDTA solution asfollows:1 mL of EDTA solution 5 50.0/V! 5 C mg of calcium (1)where:V = millilitres of EDTA used.NOTE 1If a sample with a known CaF2conte
28、nt is available, thestandardization with CaCO3can be omitted. The “standard” CaF2sampleshould then be carried through all steps of the procedure.11.2 CalibrationTransfer 10 mL of acetic acid (1 + 10)(8.3) into a series of seven 100-mL polyethylene beakers andadd 20 mL of potassium acetate buffer (8.
29、7)(Note 2). Addstandard fluoride solution (8.10) and water according to thefollowing:Test Standard FmL Solution mg Water, mL10052 0.5 0.05 4.53 1.0 0.10 4.04 2.0 0.20 3.05 3.0 0.30 2.06 4.0 0.40 1.07 5.0 0.50 0Stir the solution, immerse the electrodes (7.1 and 7.5) andwait for 3 min to 5 min for pot
30、ential to reach equilibrium.Record the potential in millivolts. Plot millivolts (linear scale)versus Fconcentration in milligrams (log scale).NOTE 2Potential measurements in calibration standards and sampleshould be carried out concurrently.12. Procedure12.1 Determination of Total Calcium:12.1.1 Tra
31、nsfer approximately 0.50 g of the sample to asmall weighing bottle, previously dried at about 105 C. Drythe bottle and contents for1hat105Cto110C.Capthebottle and cool to room temperature in a desiccator. Momen-tarily release the cap to equalize the pressure and weigh thecapped bottle to the nearest
32、 0.1 mg. Repeat the drying andweighing until there is no further loss of mass. Transfer the4Thermo Scientific Orion model 90-01-00 Single Junction Reference Electrodehas been found suitable for this purpose.5Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washi
33、ngton, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see the United States Pharmacopeia andNational Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.E815 112sample to a 400-mL beaker and reweigh the capped bottle tothe nearest 0.1 mg.
34、The difference between the two weights isthe mass of the sample taken for analysis.12.1.2 Decomposition of SampleAdd 5 mL of HNO3,cover with a watch glass, and digest on a hot plate. Coolsomewhat, add 5 mL of HClO4, and evaporate first to fumes ofHClO4. When decomposition appears to be complete, til
35、t thecover and evaporate carefully to complete dryness. Allow tocool, add 5 mL of HCl, dilute to approximately 50 mL withwater, and heat until all the soluble salts have dissolved. Thisis the main solution.NOTE 3If an insoluble residue remains, filter through a fine-texturedpaper, wash the paper tho
36、roughly with hot HCl, ignite the paper andresidue in a platinum crucible, treat the insoluble residue again with HNO3and HClO4as in sample decomposition, and combine this solution withthe main filtrate. If the volume exceeds 90 mL, evaporate the volume toabout 80 mL and cool.12.1.3 Transfer the solu
37、tion to a 100-mL volumetric flask,dilute to volume, and mix.12.1.4 Transfer an appropriate aliquot (20.00 mL in therange from 80 % to 100 % CaF2and 25.00 mL in the rangefrom 40 % to 80 % CaF2) to a 400-mL beaker. Add 5 mL oftriethanolamine (8.11). Make the solution just alkaline withpotassium hydrox
38、ide solution A (8.8) and add 15 mL ofadditional KOH solutionA(8.8). Titrate with EDTAsolution asdescribed in 11.1.1.NOTE 4As used in this test method (except as related to the termrelative standard deviation), “percent or “%” refers to mass fraction(wt/wt) of the form g/100g.12.2 Determination of So
39、luble Calcium:12.2.1 Transfer 1.00 g of sample to a 250-mL beaker. Add20 mL of acetic acid (1 + 10) (8.3) and digest at just belowboiling point for 60 min. Cool, filter through a fine-texturedfilter paper, and wash five times with acetic acid (1 + 10) (8.3),collecting the filtrate and washings into
40、a 50-mL volumetricflask. Dilute the contents to mark with water.12.2.2 Pipet a 25-mL aliquot into a 400-mL beaker andevaporate to dryness. Redissolve the residue in 1 to 2 mL ofHCL and dilute to 200 mL with water. Add 5 mL of trietha-nolamine (8.11) and proceed as in total calcium determination.Reco
41、rd the titration. Calculate milligrams of calcium (X) in the50-mL volume by multiplying the titration (in millilitres) by2C (proceed as in 11.1).12.2.3 Transfer a 10-mLaliquot into a 100-mLpolyethylenebeaker, add 20 mL of potassium acetate buffer (8.7)and5mLof water (Note 2), and mix (pH should be 5
42、.0). Measure thepotential in millivolts using reference and fluoride ion-selectiveelectrodes as described in 11.2. Obtain the milligrams of Fbyreferring to the graph in 11.2.13. Calculation13.1 Calculate total calcium as follows:Total calcium, % T 510VCab(2)where:V = volume of titrant, mL,C = calciu
43、m equivalent of EDTA solution, mg/mL,a = millilitres of aliquot,b = grams of sample used, andT = total calcium present,% .13.2 Calculate soluble calcium as follows:Soluble calcium, % S 52!V!C! 2 5.2737!F2!10(3)where:V = volume of titrant, mL,C = calcium equivalent of EDTA solution, mg/mL,F = fluorid
44、e ion content, mg.13.3 Calculate calcium fluoride as follows:Calcium fluoride, % 5 T 2 S! 3 1.948 (4)where:T = total calcium percent found in 13.1, andS = soluble calcium percent found in 13.2.14. Precision and Bias614.1 PrecisionTable 1 indicates the precision of the testmethod between laboratories
45、.14.2 BiasNo information on the bias of this test method isknown. Accepted reference materials may have not beenincluded in the materials used in the interlaboratory study.Users of this test method are encouraged to employ acceptedreference materials, if available, and to judge the bias of thistest
46、method from the difference between the accepted value forthe calcium fluoride content and the mean value from inter-laboratory testing of the reference material.15. Keywords15.1 calcium content; calcium fluoride content; complexo-metric titrimetry; fluorspar; soluble calcium content6Supporting data
47、giving the results of cooperative testing are available fromASTM International Headquarters. Request RR:E16-1003.TABLE 1 Precision DataFluorspar GradeAverageCalciumFluorideContent, %RelativeStandardDeviation,%Number ofParticipatingLaboratoriesSpanish acid 97.63 0.195 14African acid 96.78 0.257 14Mex
48、ican ceramic 91.84 0.173 14Mexican metallurgical 87.72 0.263 14E815 113ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of
49、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 receive careful consideration at a meeting of theresponsible technical committee, which you may
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