1、Designation: E815 11E815 17Standard 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,
2、 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 calcium fluoride in acid-grade fluorspar and other types of
3、fluorspar that canbe rendered soluble by the procedure described in the test method.1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.3 This test method has been evaluated in accordance with Practice E1601 and Guide E1763.
4、 Unless otherwise noted in theprecision and bias section, the lower limit in the scope of each method specifies the lowest analyte content that may be analyzedwith acceptable error (defined as a nominal 5 % risk of obtaining a 50 % or larger relative difference in results on the same testsample in t
5、wo laboratories).1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.
6、1.5 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Tr
7、ade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterE29 Practice for Using Significant Digits in Test Data to Determine Conformance with SpecificationsE50 Practices forApparatus, Reagents, and Safety Considerations for ChemicalAnalysis of Metals, Ores,
8、 and Related MaterialsE135 Terminology Relating to Analytical Chemistry for Metals, Ores, and Related MaterialsE276 Test Method for Particle Size or ScreenAnalysis at No. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores and RelatedMaterialsE882 Guide for Accountability and Quality Control in the C
9、hemical Analysis LaboratoryE1601 Practice for Conducting an Interlaboratory Study to Evaluate the Performance of an Analytical MethodE1763 Guide for Interpretation and Use of Results from Interlaboratory Testing of Chemical Analysis Methods (Withdrawn2015)33. Terminology3.1 DefinitionsFor definition
10、s of terms used in this test method, refer to Terminology E135.4. Summary of Test Method4.1 The sample is decomposed by digesting with nitricHNO3 and perchloricHCLO4 acids and the fluorine is expelled by fuming.The residue is dissolved in dilute hydrochloric acid, HCL, the solution made alkaline, an
11、d the calcium titrated with standard EDTAsolution. Calcium present as carbonate is determined in a separate sample with EDTA solution, after extracting the former with1 This test method is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials an
12、d is the direct responsibility ofSubcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials.Current edition approved Sept. 1, 2011May 1, 2017. Published September 2011July 2017. Originally approved in 1981. Last previous edition approved in 20042011 asE815 04.11. DOI: 10.1520/E08
13、15-11.10.1520/E0815-17.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 The last approved version of this hi
14、storical standard is referenced on www.astm.org.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurate
15、ly, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1
16、dilute acetic acid. A correction for calcium fluoride, solubilized by dilute acetic acid digestion, is applied,applied by determiningthe fluoride in the acetic acid extract by fluoride ion-selective electrode. The CaF2 content is then calculated.5. Significance and Use5.1 Fluorspar is used as a flux
17、 in steelmaking, the steelmaking and glass industry, and in the manufacture of hydrofluoricacid.HF.5.2 This test method is intended to be used for compliance with compositional specifications for calcium fluoride content. It isassumed that all who use these procedures will be trained analysts capabl
18、e of performing common laboratory procedures skillfullyand safely. It is expected that work will be performed in a properly equipped laboratory and that proper waste disposal procedureswill be followed. Appropriate quality control practices must be followed such as those described in Guide E882.6. I
19、nterferences6.1 None of the elements normally found in fluorspar interfere with this test method.7. Apparatus7.1 Fluoride Ion-Selective Electrode. 47.2 Magnetic Stirrer and TFE-Fluorocarbon-Coated Spin Bar.7.3 pH Meter with High ImpedanceSuitable for ion-selective electrode.7.4 Polyethylene Beakers,
20、 100-mL.7.5 Single Junction Ag/AgCl Reference Electrode. 58. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the Americ
21、an Chemical Society where suchspecifications are available.6 Other grades may be used, provided it is first ascertained that the reagent is of sufficient high purityto permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, references to wate
22、r shall be understood to mean reagent water conforming toType I or II of Specification D1193. Type III or IV may be used if they effect no measurable change in the blank or sample.8.3 Acetic Acid Solution (1 + 10) Mix 1 volume of glacial acetic acid (CH3COOH) with 10 volumes of water.8.4 Calcium Car
23、bonate, high purity (minimum 99.95 % CaCO3).8.5 Ethylenediaminetetraacetic Acid Disodium Salt (EDTA)-Na2C1100H1 144O8N22H2O Solution (0.025 mol/L)Dissolve9.3062 g of EDTA in water, transfer to a 1-L volumetric flask, dilute to volume, and mix.8.6 Hydroxynaphthol Blue Indicator Grind 0.2 g of the sal
24、t with 50 g sodium chloride (NaCl).8.7 Potassium Acetate BufferDilute 283 mL of glacial acetic acid (CH3COOH) to 1200 mL with water. While cooling andstirring, add potassium hydroxide KOH solution B (KOH) (8.9) to adjust the pH to 5.0 (approximately 350 mL of KOH solutionB are required).8.8 Potassiu
25、m Hydroxide Solution ADissolve 225 g of potassium hydroxide (KOH) KOH in water and dilute to 1 L withwater. Store in a plastic bottle.8.9 Potassium Hydroxide Solution BDissolve 500 g of potassium hydroxide (KOH) KOH in water and dilute to 1 L. Storein a plastic bottle.8.10 Sodium Fluoride SolutionDi
26、ssolve 0.2210 g sodium fluoride (NaF) in water in a polyethylene beaker and dilute to 1 Lin a volumetric flask. Store in a stoppered polyethylene bottle. This solution has a concentration of 1 mL = 0.10 mg F and is stablefor 6 months.8.11 Triethanolamine Solution (1 + 1) Mix 50 mL of triethanolamine
27、 (NC6H1 155O3) with 50 mL of water.9. Hazards9.1 For precautions to be observed in this method, refer to Practice E50.4 Thermo Scientific Orion model 94-91 has been found suitable for this purpose.5 Thermo Scientific Orion model 90-01-00 Single Junction Reference Electrode has been found suitable fo
28、r this purpose.6 Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American Chemical Society, see the United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, In
29、c. (USPC), Rockville, MD.E815 17210. Sampling, Test Specimens, and Test Units10.1 Pulverize the test units so that 95 % passes a No. 100 mesh sieve (150-m) in accordance withas directed in Test MethodsE276.11. Calibration and Standardization11.1 StandardizationWeigh and transfer 2.4970 g of CaCO3 (d
30、ried at 110 C for 1 h and cooled in a desiccator) to a 600-mLbeaker. Using a hood and appropriate personal protective equipment, cautiously add 75 mL of HCl and warm. Cool, transfer toa 1-L volumetric flask, dilute to volume with water, and mix. This solution has a concentration of 1 mL = 1.0000 mg
31、of calcium.11.1.1 Titration:11.1.1.1 Transfer a 50.00-mL aliquot of this solution to a 400-mL beaker, add 5 mL of triethanolamine (8.11), dilute to 200 mL,make just alkaline with potassium hydroxide KOH solution A (8.8), using a strip of litmus paper, and then add an additional 15mL of potassium hyd
32、roxide KOH solution A (8.8).11.1.1.2 Add 0.2 g of hydroxynaphthol blue indicator and titrate 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 as follows:1mL of EDTA solution550.0/V! 5C m
33、g of calcium (1)where:V = millilitres of EDTA used.V = milliliters of EDTA used.NOTE 1If a sample with a known CaF2 content is available, the standardization with CaCO3 can be omitted. The “standard” CaF2 sample should thenbe carried through all steps of the procedure.11.2 CalibrationTransfer 10 mL
34、of acetic acid (1 + 10) (8.3) into a series of seven 100-mL polyethylene beakers and add 20mL of potassium acetate buffer (8.7) (Note 2). Potential measurements in calibration standards and sample should be carried outconcurrently. Add standard fluoride solution (8.10) and water according to the fol
35、lowing:as follows:Test Standard F mL Solution mg Water, mL1 0 0 52 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) and wait for 3 min to 5 min for potential to reach equilibrium. Recordthe potential in millivolts
36、. Plot millivolts (linear scale) versus F concentration in milligrams (log scale).NOTE 2Potential measurements in calibration standards and sample should be carried out concurrently.12. Procedure12.1 Determination of Total Calcium:12.1.1 Transfer approximately 0.50 g of the sample to a small weighin
37、g bottle, previously dried at about 105 C. Dry the bottleand contents for 1 h at 105 C to 110 C. Cap the bottle and cool to room temperature in a desiccator. Momentarily release thecap to equalize the pressure and weigh the capped bottle to the nearest 0.1 mg. Repeat the drying and weighing until th
38、ere is nofurther loss of mass. Transfer the sample to a 400-mL beaker and reweigh the capped bottle to the nearest 0.1 mg. The differencebetween the two weightsmasses is the 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
39、a hot plate. Cool somewhat,add 5 mL of HClO4, and evaporate first to fumes of HClO4. When decomposition appears to be complete, tilt the cover andevaporate carefully to complete dryness.Allow to cool, add 5 mLof HCl, dilute to approximately 50 mLwith water, and heat untilall the soluble salts have d
40、issolved. This is the main solution.NOTE 2If an insoluble residue remains, filter through a fine-textured paper, wash the paper thoroughly with hot HCl, ignite the paper and residuein a platinum crucible, treat the insoluble residue again with HNO3 and HClO4 as in sample decomposition, and combine t
41、his solution with the mainfiltrate. If the volume exceeds 90 mL, evaporate the volume to about 80 mL and cool.12.1.3 Transfer the solution to a 100-mL volumetric flask, dilute to volume, and mix.12.1.4 Transfer an appropriate aliquot (20.00 mL in the range from 80 % to 100 % CaF2 and 25.00 mL in the
42、 range from 40% to 80 % CaF2) to a 400-mL beaker. Add 5 mL of triethanolamine (8.11). Make the solution just alkaline with potassiumhydroxide KOH solution A (8.8) and add 15 mL of additional KOH solution A (8.8). Titrate with EDTA solution as described in11.1.1.NOTE 3As used in this test method (exc
43、ept as related to the term relative standard deviation), “percent or “%” refers to mass fraction (wt/wt) of theform g/100g.12.2 Determination of Soluble Calcium:E815 17312.2.1 Transfer 1.00 g of sample to a 250-mL beaker. Add 20 mL of acetic acid (1 + 10) (8.3) and digest at just below boilingpoint
44、for 60 min. Cool, filter through a fine-textured filter paper, and wash five times with acetic acid (1 + 10) (8.3), collecting thefiltrate and washings into a 50-mL volumetric flask. Dilute the contents to mark with water.12.2.2 Pipet a 25-mL aliquot into a 400-mL beaker and evaporate to dryness. Re
45、dissolve the residue in 1 mL to 2 mL of HCLand dilute to 200 mL with water. Add 5 mL of triethanolamine (8.11) and proceed as in total calcium determination. Record thetitration. Calculate milligrams of calcium (X) in the 50-mL volume by multiplying the titration (in millilitres)milliliters) by 2C(p
46、roceed as in 11.1).12.2.3 Transfer a 10-mL aliquot into a 100-mL polyethylene beaker, add 20 mL of potassium acetate buffer (8.7) and 5 mL ofwater (water, Note 2), and mix (pH should be 5.0). Measure the potential in millivolts using reference and fluoride ion-selectiveelectrodes as described in 11.
47、2. Obtain the milligrams of F by referring 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 = calcium equivalent of EDTA solution, mg/mL,a = millilitres of aliquot,a = milliliters of aliquot,b = grams of sample
48、used, andT = total calcium present,% .13.2 Calculate soluble calcium as follows:Soluble calcium,%S 52!V!C!25.2737!F2!10 (3)where:V = volume of titrant, mL,C = calcium equivalent of EDTA solution, mg/mL,F = fluoride ion content, mg.F = fluoride ion content, mg.13.3 Calculate calcium fluoride as follo
49、ws:Calcium fluoride,%5T 2S! 31.948 (4)where:T = total calcium percent found in 13.1, andS = soluble calcium percent found in 13.2.13.4 Rounding of test results obtained using this test method shall be performed in accordance with Practice E29, RoundingMethod, unless an alternative rounding method is specified by the customer or applicable material specification.14. Precision and Bias714.1 PrecisionTable 1 indicates the precision of the test method between laboratories.7 Supporting data giving the results of cooperative testing are availabl
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