1、Designation: E815 17E815 17aStandard 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 rev
2、ision, 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 typ
3、es 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 testsampl
5、e 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 safety, health, and healthenvironmental practices and determine theapplicability of r
6、egulatory limitations 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 Or
7、ganization Technical 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 fo
8、r ChemicalAnalysis 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 Accounta
9、bility and Quality 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. Termi
10、nology3.1 DefinitionsFor 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 HCLOHClO4 and the fluorine is expelled by fuming. The residueis dissolved in dilute HCL,HCl, the solution made alkaline,
11、and the calcium titrated with standard EDTAsolution. Calcium presentas carbonate is determined in a separate sample with EDTAsolution, after extracting the former with dilute acetic acid.Acorrection1 This test method is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals,
12、 Ores, and Related Materials and is the direct responsibility ofSubcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials.Current edition approved May 1, 2017Sept. 15, 2017. Published July 2017October 2017. Originally approved in 1981. Last previous edition approved in 20112017
13、as E815 11.17. DOI: 10.1520/E0815-17.10.1520/E0815-17A.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
14、last approved 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 adequa
15、tely depict all 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 Conshohocke
16、n, PA 19428-2959. 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 s
17、teelmaking and glass industry,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 labor
18、atory 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. Interferences6.1 None of the
19、elements normally found in fluorspar interfereinterferes 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
20、Junction Ag/AgCl Reference Electrode.58. Reagents and Materials8.1 Purity of ReagentsReagent grade Reagent-grade chemicals shall be used in all tests. Unless otherwise indicated, it isintended that all reagents conform to the specifications of the Committee onAnalytical Reagents of theAmerican Chemi
21、cal Societywhere such specifications are available.6 Other grades may be used, provided it is first ascertained that the reagent is of sufficienthigh purity to permit its use without lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, references to water shall
22、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 Carbonate, h
23、igh purity (minimum 99.95 % CaCO3).8.5 Ethylenediaminetetraacetic 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 so
24、dium chloride (NaCl).8.7 Potassium Acetate 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
25、 KOH in water and dilute to 1 L with water. 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 L
26、in a volumetric flask. Store in a stoppered polyethylene bottle. This solution has a concentration of 1 mL = 0.10 mg F and is stablefor 6six 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 me
27、thod, refer to PracticePractices E50.10. Sampling, Test Specimens, and Test Units10.1 Pulverize the test units so that 95 % passes a No. 100 mesh sieve (150-m) as directed in Test MethodsMethod E276.4 Thermo Scientific Orion model 94-91 has been found suitable for this purpose.5 Thermo Scientific Or
28、ion model 90-01-00 Single Junction Reference Electrode has 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 Uni
29、ted States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.E815 17a211. 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 appro
30、priate 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 1 mL = 1.0000mg of calcium.11.1.1 Titration:11.1.1.1 Transfer a 50.00-mL aliquot of this solut
31、ion to a 400-mL beaker, add 5 mL of triethanolamine (8.11), dilute to 200 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
32、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 mg of calcium (1)where:V = milliliters of EDTA used.NOTE 1If a sample with a known CaF2 content is available, the standa
33、rdization with CaCO3 can be omitted. The “standard” CaF2 sample should thenbe 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 measureme
34、nts in calibration standards and sample should be carried outconcurrently. 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 electr
35、odes (7.1 and 7.5) and wait for 3 min to 5 min for potential to reach equilibrium. 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
36、 a small weighing 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 w
37、eighing until there 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 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 d
38、igest on 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 mL of HCl, dilute to approximately 50 mL with water, and heat untilall the soluble s
39、alts have dissolved. 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, an
40、d combine this 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 25.0
41、0 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 3As used in this test method (except as r
42、elated to the term relative standard deviation), “percent“percent” or “%” refers to mass fraction (wt/wt)of the 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
43、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. Redissolv
44、e the residue in 1 mL to 2 mL ofHCLHCl and dilute to 200 mL with water. Add 5 mL of triethanolamine (8.11) and proceed as in total calcium determination.Record the titration. Calculate milligrams of calcium in the 50-mL volume by multiplying the titration (in milliliters) by 2C(proceed as in 11.1).E
45、815 17a312.2.3 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
46、 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 = milliliters of aliquot,b = grams of sample used, andT = total calcium present,% .T = total calciu
47、m 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, andF = fluoride ion content, mg.13.3 Calculate calcium fluoride as follows:Calcium fluoride,%5T 2S! 31.948 (4)where:T = to
48、tal 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
49、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 interlaboratory study. Users of this test method are encouraged to employ accepted reference materials,if available, and to judge the bias of this test method from the difference between the accepted value for the calcium fluoridecontent and the mean value from interlabora
