1、Designation: E 815 04Standard Test Method forDetermination of Calcium Fluoride in Fluorspar byComplexometric Titration1This standard is issued under the fixed designation E 815; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear 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 This test method covers the determination of calciumfluoride in acid-grade fluorspar and other types of fluors
3、par thatcan be rendered soluble by the procedure described in the testmethod.1.2 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 determ
4、ine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE 50 Practices for Apparatus, Reagents, and Safety Precau-tions for Chemical Analysis of Metals, Ores, and RelatedMaterialsE 135 Terminology Relating to Anal
5、ytical Chemistry forMetals, Ores, and Related MaterialsE 276 Test Methods 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 Laboratory3. Terminology3.1 Definitio
6、nsFor definitions of terms used in this testmethod, refer to Terminology E 135.4. Summary of Test Method4.1 The sample is decomposed by digesting with nitric andperchloric acids and the fluorine is expelled by fuming. Theresidue is dissolved in dilute hydrochloric acid, the solutionmade alkaline, an
7、d the calcium titrated with standard EDTAsolution. Calcium present as carbonate is determined in aseparate sample with EDTA solution, after extracting theformer with dilute acetic acid. A correction for calciumfluoride, solubilized by dilute acetic acid digestion, is applied,by determining the fluor
8、ide 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 steelmaking, glass industry,and manufacture of hydrofluoric acid.5.2 This test method is intended to be used for compliancewith compositiona
9、l specifications for calcium fluoride content.It is assumed that all who use these procedures will be trainedanalysts capable of performing common laboratory proceduresskillfully and safely. It is expected that work will be performedin a properly equipped laboratory and that proper wastedisposal pro
10、cedures will be followed. Appropriate qualitycontrol practices must be followed such as those described inGuide E 882.6. Interferences6.1 None of the elements normally found in fluorsparinterfere with this test method.7. Apparatus7.1 Fluoride Ion-Selective Electrode.37.2 Magnetic Stirrer and TFE-Flu
11、orocarbon-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 ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated
12、, it is intended thatall reagents conform to the specifications of the Committee on1This 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 Relate
13、d Metal-lurgical Materials.Current edition approved May 1, 2004. Published June 2004. Originallyapproved in 1981. Last previous edition approved in 1999 as E 815 99.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Bo
14、ok of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Orion model 94-91 has been found suitable for this purpose.4Orion model 90-01-00 has been found suitable for this purpose.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West C
15、onshohocken, PA 19428-2959, United States.Analytical Reagents of the American Chemical Society wheresuch specifications are available.5Other grades may be used,provided it is first ascertained that the reagent is of sufficienthigh purity to permit its use without lessening the accuracy ofthe determi
16、nation.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 Acetic Acid Solution (1 + 10)Mix 1 volume of glacialacetic acid (CH3COOH) with 10 volumes of water.8.4 Calcium Carbonate, high purity (mi
17、nimum 99.95 %CaCO3).8.5 Ethylenediaminetetraacetic Acid Disodium Salt(EDTA)-Na2C10H14O8N22H2O Solution (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 Hydrochloric Acid (2 + 98)Mix 2 volumes of concen-trated hydrochloric acid (HCl) wi
18、th 98 volumes of water.8.7 Hydrochloric Acid (1 + 10)Mix 1 volume of concen-trated hydrochloric acid (HCl) with 10 volumes of water.8.8 Hydroxynaphthol Blue Indicator Grind 0.2 g of thesalt with 50 g sodium chloride (NaCl).8.9 Potassium Acetate BufferDilute 283 mL of glacialacetic acid (CH3COOH) to
19、1200 mL with water. While coolingand stirring, add 50 % (W/V) potassium hydroxide solution(KOH) to adjust the pH to 5.0 (approximately 350 mL of KOHsolution are required).8.10 Potassium Hydroxide Solution (22.5 %) (W/V)Dissolve 225 g of potassium hydroxide (KOH) in water anddilute to 1 L with water.
20、 Store in a plastic bottle.8.11 Potassium Hydroxide Solution (50 %) (W/V)Dissolve 500 g of potassium hydroxide (KOH) in water anddilute to 1 L. Store in a plastic bottle.8.12 Sodium Fluoride SolutionDissolve 0.2210 g sodiumfluoride (NaF) in water in a polyethylene beaker and dilute to1 L in a volume
21、tric flask. Store in a stoppered polyethylenebottle. This solution has a concentration of 1 mL = 0.10 mg Fand is stable for 6 months.8.13 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 to
22、Practice E 50.10. Sampling, Test Specimens, and Test Units10.1 Pulverize the test units so that 95 % passes a No. 100mesh sieve (150-m) in accordance with Test Methods E 276.11. Calibration and Standardization11.1 StandardizationWeigh and transfer 2.4970 g ofCaCO3(dried at 110C for 1 h and cooled in
23、 a desiccator) to a600-mL beaker. While covered, cautiously add 75 mL of HCl(8.7) and warm. Cool, transfer to a 1-L volumetric flask, diluteto volume with water, and mix. This solution has a concentra-tion of 1 mL = 1.0000 mg of calcium.11.1.1 Titration11.1.1.1 Transfer a 50.00-mL aliquot of this so
24、lution to a400-mL beaker, add 5 mL of triethanolamine (8.13), dilute to200 mL, make just alkaline with potassium hydroxide solution(8.10), using a strip of litmus paper, and then add an additional15 mL of potassium hydroxide solution (8.10).11.1.1.2 Add 0.2 g of hydroxynaphthol blue indicator andtit
25、rate 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 CaF2
26、content 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 buffe
27、r (8.9) (Note 2). Addstandard fluoride solution (8.12) 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 to 5 min for p
28、otential to reach equilibrium. Recordthe potential in millivolts. Plot millivolts (linear scale) versusFconcentration in milligrams (log scale) on a semilog paper.NOTE 2Potential measurements in calibration standards and sampleshould be carried out concurrently.12. Procedure12.1 Determination of Tot
29、al Calcium:12.1.1 Transfer approximately 0.50 g of the sample to asmall weighing bottle, previously dried at about 105C. Drythe bottle and contents for1hat105to110C. Cap the bottleand cool to room temperature in a desiccator. Momentarilyrelease the cap to equalize the pressure and weigh the cappedbo
30、ttle to the nearest 0.1 mg. Repeat the drying and weighinguntil there is no further weight loss. Transfer the sample to a400-mL beaker and reweigh the capped bottle to the nearest 0.1mg. The difference between the two weights is the weight ofthe sample taken for analysis.12.1.2 Decomposition of Samp
31、leAdd 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, tilt thecover and evaporate carefully to complete dryness. Allow to5Reagent Chemicals, American Chemical Society S
32、pecifications, 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 National Formulary, U.S. Pharmaceutical C
33、onvention, Inc. (USPC), Rockville,MD.E815042cool, 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, and wash the paper thoroughly with hot
34、 HCl (8.6), ignite the paperand residue in a platinum crucible, and treat the insoluble residue againwith HNO3and HClO4as in sample decomposition, and combine thissolution with the main filtrate. If the volume exceeds 90 mL, evaporate itto about 80 mL and cool.12.1.3 Transfer the solution to a 100-m
35、L 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 range from40 to 80 % CaF2) to a 400-mL beaker. Add 5 mL of trietha-nolamine (8.13). Make the solution just alkaline with potas-sium hydroxide solution (8
36、.10) and add 15 mL of additionalKOH solution (8.10). Titrate with EDTA solution as describedin 11.1.1.12.2 Determination of Soluble 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 throu
37、gh a fine-texturedfilter paper, and wash five times with acetic acid (1 + 10) (8.3),collecting the filtrate and washings into 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
38、 ofhydrochloric acid and dilute to 200 mL with water. Add 5 mLof triethanolamine (8.13) and proceed as in total calciumdetermination. Record the titration. Calculate milligrams ofcalcium (X) in the 50-mL volume by multiplying the titration(in millilitres) by 2C (proceed as in 11.1).12.2.3 Transfer a
39、 10-mL aliquot into a 100-mL polyethylenebeaker, add 20 mL of potassium acetate buffer (8.9) and 5 mLof water (Note 2), and mix (pH should be 5.0). Measure thepotential in millivolts using reference and fluoride ion-selectiveelectrodes as described in 11.2. Obtain the milligrams of Fbyreferring to t
40、he graph in 11.2.13. Calculation13.1 Calculate total calcium as follows:Total calcium, % T 5 10!V!C!/a!b! (2)where:V = volume of titrant, mL,C = calcium equivalent of EDTA solution, mg/mL,a = millilitres of aliquot,b = grams of sample used, andT = total calcium present,% .13.2 Calculate soluble calc
41、ium 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 = fluoride ion concentration, 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 1
42、3.1, andS = soluble calcium percent found in 13.2.14. Precision and Bias614.1 PrecisionTable 1 indicates the precision of the testmethod between laboratories.14.2 BiasNo information on the bias of this test method isknown. Accepted reference materials may have not beenincluded in the materials used
43、in the interlaboratory study.Users of this test method are encouraged to employ acceptedreference materials, if available, and to judge the bias of thistest method from the difference between the accepted value forthe calcium fluoride content and the mean value from inter-laboratory testing of the r
44、eference material.15. Keywords15.1 calcium content; calcium fluoride content; fluorspar;soluble calcium content6Supporting data giving the results of cooperative testing are available fromASTM International Headquarters. Request RR: E16-1003.TABLE 1 Precision DataFluorspar GradeAverageConcentration,
45、 %RelativeStandardDeviation,A%Number ofParticipatingLaboratoriesSpanish acid 97.63 0.195 14African acid 96.78 0.257 14Mexican ceramic 91.84 0.173 14Mexican metallurgical 87.72 0.263 14ACalculate the relative standard deviation, RSD, in this test method as follows:RSD 5 100/ X! =(d2/n 2 1!where:X= av
46、erage concentration, %,d = difference of the determination from the mean, andn = number of determinations.E815043ASTM 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 advi
47、sed 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
48、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 attend. If
49、 you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E815044
