1、Designation: E815 17aE815 17bStandard Test Method forDetermination of Calcium Fluoride in Fluorspar by EDTAComplexometric 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 re
2、vision, 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 ty
3、pes of 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
4、 E1763. 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 testsamp
5、le in two 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, health, and environmental practices and determine the applicability ofregulatory li
6、mitations prior to use.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 T
7、echnical Barriers to Trade (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 ChemicalAn
8、alysis of Metals, Ores, 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 Q
9、uality Control in the Chemical 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 De
10、finitionsFor definitions of terms used in this test method, refer to Terminology E135.4. Summary of Test Method4.1 The sample is decomposed by digesting with HNO3 and HClO4 and the fluorine is expelled by fuming. The residue isdissolved in dilute HCl, the solution made alkaline, and the calcium titr
11、ated with standard EDTA solution. Calcium present ascarbonate is determined in a separate sample with EDTA solution, after extracting the former with dilute acetic acid. A correction1 This test method is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Relat
12、ed Materials and is the direct responsibility ofSubcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials.Current edition approved Sept. 15, 2017Nov. 15, 2017. Published October 2017December 2017. Originally approved in 1981. Last previous edition approved in 2017 asE815 17.17a.
13、 DOI: 10.1520/E0815-17A.10.1520/E0815-17B.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
14、 version of this historical 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 a
15、ll changes accurately, 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 19428-2
16、959. United States1for calcium fluoride, solubilized by dilute acetic acid digestion, is applied by determining the fluoride in the acetic acid extract byfluoride ion-selective electrode. The CaF2 content is then calculated.5. Significance and Use5.1 Fluorspar is used as a flux in the steelmaking an
17、d glass industries, and in the manufacture of 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 capable of performing common laboratory procedures skill
18、fullyand 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. Interferences6.1 None of the elements normally foun
19、d in fluorspar interferes 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, 100-mL.7.5 Single Junction Ag/AgCl Reference Elec
20、trode.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 American Chemical Society where suchspecifications are av
21、ailable.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 water shall be understood to mean reagent water conform
22、ing 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 Carbonate, high purity (minimum 99.95 % CaCO3).8.5 Ethy
23、lenediaminetetraacetic Acid Disodium Salt (EDTA)-Na2C10H14O8N22H2O Solution (0.025 mol/L)Dissolve 9.3062g 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 salt with 50 g sodium chloride (NaCl).8.7 Potassium Acetate
24、BufferDilute 283 mL of glacial acetic acid (CH3COOH) to 1200 mL with water. While cooling andstirring, add KOH solution B (8.9) to adjust the pH to 5.0 (approximately 350 mL of KOH solution B are required).8.8 Potassium Hydroxide Solution ADissolve 225 g of KOH in water and dilute to 1 L with water.
25、 Store in a plastic bottle.8.9 Potassium Hydroxide Solution BDissolve 500 g of KOH in water and dilute to 1 L. Store in a plastic bottle.8.10 Sodium Fluoride SolutionDissolve 0.2210 g sodium fluoride (NaF) in water in a polyethylene beaker and dilute to 1 Lin a volumetric flask. Store in a stoppered
26、 polyethylene bottle. This solution has a concentration of 1 mL = 0.10 mg F and is stablefor six months.8.11 Triethanolamine Solution (1 + 1)Mix 50 mL of triethanolamine (NC6H15O3) with 50 mL of water.9. Hazards9.1 For precautions to be observed in this method, refer to Practices E50.10. Sampling, T
27、est Specimens, and Test Units10.1 Pulverize the test units so that 95 % passes a No. 100 mesh sieve (150-m) as directed in Test Method E276.4 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
28、been found suitable for 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. Pharma
29、copeial Convention, Inc. (USPC), Rockville, MD.E815 17b211. Calibration and Standardization11.1 StandardizationWeigh and transfer 2.4970 g of CaCO3 (dried 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
30、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 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 20
31、0 mL,make just alkaline with KOH solution A (8.8), using a strip of litmus paper, and then add an additional 15 mL of KOH solutionA (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 pin
32、k to blue. Determine the calcium equivalent of the EDTA solution as follows:1mL of EDTA solution550.0/V! 5C mg of calcium (1)where: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 t
33、henbe 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 and add 20mL of potassium acetate buffer (8.7). Potential measurements in calibration standards and sample should be carried outconcurrentl
34、y. Add standard fluoride solution (8.10) and water 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 eq
35、uilibrium. Recordthe potential in millivolts. Plot millivolts (linear scale) versus F concentration in milligrams (log scale).12. Procedure12.1 Determination of Total Calcium:12.1.1 Transfer approximately 0.50 g of the sample to a small weighing bottle, previously dried at about 105 C. Dry the bottl
36、eand 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 there is nofurther loss of mass. Transfer the sample to a
37、400-mL beaker and reweigh the capped bottle to the nearest 0.1 mg. The differencebetween the two masses 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 a hot plate. Cool somewhat,add 5 mL of HClO4, and evaporate fir
38、st to fumes of HClO4. When decomposition appears to be complete, tilt the cover andevaporate carefully to complete dryness.Allow to cool, add 5 mL of HCl, dilute to approximately 50 mL with water, and heat untilall the soluble salts have dissolved. This is the main solution.NOTE 2If an insoluble res
39、idue 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 this solution with the mainfiltrate. If the volume exceeds 90
40、mL, evaporate the volume to about 80 mL and cool.12.1.2.1 If an insoluble residue remains, filter through a fine-textured paper, wash the paper thoroughly with hot HCl, ignite thepaper and residue in a platinum crucible, treat the insoluble residue again with HNO3 and HClO4 as in sample decompositio
41、n, andcombine this solution with the main filtrate. 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
42、 25.00 mL in the range from 40% to 80 % CaF2) to a 400-mL beaker. Add 5 mL of triethanolamine (8.11). Make the solution just alkaline with KOH solution A(8.8) and add 15 mL of additional KOH solution A (8.8). Titrate with EDTA solution as described in 11.1.1.NOTE 2As used in this test method (except
43、 as related to the term relative standard deviation), “percent” or “%” refers to mass fraction (wt/wt) ofthe form g/100g.12.2 Determination of Soluble Calcium:12.2.1 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 for 60 min
44、. 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.E815 17b312.2.2 Pipet a 25-mL aliquot into a 400-mL beaker and evaporate to dryness. Red
45、issolve 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 in the 50-mL volume by multiplying the titration (in milliliters) by 2C (proceed as in11.1
46、).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, and mix (pH should be 5.0). Measure the potential in millivolts using reference and fluoride ion-selective electrodes asdescribed in 11.2. Obtain the milligrams of F by
47、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 = milliliters of aliquot,b = grams of sample used, andT = total calcium present, %.13.2 Calculate soluble
48、 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, andF = fluoride ion content, mg.13.3 Calculate calcium fluoride as follows:Calcium fluoride,%5T 2S! 31.948 (4)where:T = total calcium percent found in 13.1,
49、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.14.2 BiasNo information on the bias of this test method is known. Accepted reference materials may have not been includedin the materials used in the interla
