1、Designation: E 2296 03Standard Practice forSilver Corrections in Metal Bearing Ores, Concentrates, andRelated Metallurgical Materials by Fire Assay Slag Recyclingand Cupel Proof Gravimetry1This standard is issued under the fixed designation E 2296; the number immediately following the designation in
2、dicates the year oforiginal adoption or, in the case of revision, the year 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 practice covers the silver loss co
3、rrection, utilizingslag recycling and cupellation of proof silver during the fireassay of metal bearing ores, concentrates and related metallur-gical materials.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the use
4、r of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (See Practices E 50and ISO Guide 35.)2. Referenced Documents2.1 ASTM Standards:E 29 Practice for Using Significant Digits in Test Data toDetermine Conform
5、ance with Specifications2E 50 Practices for Apparatus, Reagents, and Safety Precau-tions for Chemical Analysis of Metals3E 135 Terminology relating to Analytical Chemistry forMetals, Ores and Related Materials3E 882 Guide for Accountability and Quality Control in theChemical Analysis of Metals32.2 O
6、ther Documents:ISO 35:1989 Certification of Reference Materials- Generaland Statistical PrinciplesISO 10378:1994 Copper Sulfide ConcentratesDetermination of Gold and Silver ContentsFire AssayGravimetric and Atomic Absorption SpectrometricMethodBugbee, Edward, Textbook of Fire Assaying4Smith, E. A.,
7、The Sampling and Assay of Precious Metals53. Terminology3.1 DefinitionsFor definitions of terms used in this Prac-tice, refer to Terminology E 135.4. Summary of Practice4.1 In the process of fire assay fusion, the slag is retainedfrom the initial fusion and reprocessed through the fusionprocedure. T
8、he resulting lead button is combined with thepreliminary lead button during cupellation. Proof silver iscarried through the cupellation procedure to determine thesilver losses. (See ISO 10378, Bugbee, Smith).5. Significance and Use5.1 This practice is primarily intended to be used for thecorrection
9、of silver loss in the fire assay process. Silvercontents are determined by fire assay for the purpose ofmetallurgical exchange between buyer and seller. It is assumedthat all who use this practice will be trained analysts capable ofperforming skillfully and safely. It is expected that work willbe pe
10、rformed in a properly equipped laboratory under appro-priate quality control practices such as those described inGuide E 882.6. Apparatus6.1 Assay Furnace, capable of temperatures up to 1100C,accurate to 6 5C with draft controls.6.2 Analytical Balance, capable of weighing to 0.001 mg.6.3 Hammer, bla
11、cksmith type.6.4 Hammering Block, flat steel or iron.1This practice is under the jurisdiction of ASTM Committee E01 on AnalyticalChemistry for Metals, Ores and Related Materials and is the direct responsibility ofSubcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials .Current
12、 edition approved June 10, 2003. Published July 2003.2Annual Book of ASTM Standards, Vol 14.02.3Annual Book of ASTM Standards, Vol 03.05.4Bugbee, E. E., A Textbook of Fire Assaying, John Wiley and Sons, Inc., ThirdEd., 1946.5Smith, E. A., The Sampling and Assay of the Precious Metals, Charles Griffi
13、nand Co., Ltd., Second Ed., 1947.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall rea
14、gents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.6Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accurac
15、y ofthe determination.7.2 Borax, sodium tetraborate (Na2B4O7), technical grade.7.3 Crucibles, standard fire assay clay.7.4 Cupels, magnesite (MgCO3) or bone ash, size deter-mined by lead button weight.NOTE 1Cupel size is determined by the weight of the lead button.Cupels must be large enough to hold
16、 all the molten lead from the primaryfire assay fusion and slag re-fusion.7.5 Lead Foil (99.99 % purity min; 1 ppm silver max).7.6 Litharge (PbO), technical grade, precious metal free.7.7 Potassium Bitartrate (K2C4H4O6), technical grade.7.8 Silica Sand (SiO2), technical grade.7.9 Silver Metal (99.99
17、 % purity), foil.7.10 Sodium Carbonate (Na2CO3), technical grade.7.11 Wax paper Flux Bag,25by25cm2.8. Hazards8.1 For precautions to be observed in this method, refer toPractice E 50.9. Procedure9.1 Perform the initial fire assay according to proper ac-cepted procedures to produce the initial lead bu
18、tton. (SeeBugbee, and Smith.)9.2 Collect the fire assay fusion slag from the original fusionand place back into the original fire assay crucible.9.3 Add 50 g of the slag re-fusion flux to the crucible. Thecomposition is shown in Table 1.9.4 Place crucible in the fire assay furnace. Raise thetemperat
19、ure to 1060C. After the furnace obtains that tempera-ture, hold for at least 30 min. In most instances, the totalfurnace time will be approximately 1 h. Fusion must be in aliquid state.NOTE 2In most cases, the best way to add re-fusion flux is with a waxpaper bag. Place the re-fusion flux into the b
20、ag, twist the top, and place ontop of the original fusion slag material in the original fire assay crucible.9.5 After 1 h, carefully pour the melt into fire assay moulds,taking care to ensure that no portion is lost.9.6 After cooling, break off slag and retain lead button.9.7 Place the re-fusion lea
21、d button with the original fusionlead button for each test sample.9.8 Weight two proof silver foil samples to match thetypical weight of the expected dor bead and record theweights. If the weight of the dor bead is unknown, weigh twoproof silver samples approximately 75 to 100 mg and 250 to350 mg.9.
22、9 Wrap the proof silver beads in lead foil, pound into alead square with a hammer.NOTE 3The weight of the lead foil should approximate the weigh ofthe combined lead buttons collected in 9.1 and 9.6.9.10 Transfer the lead square (9.9) and the combined leadbuttons (9.7) into the cupellation furnace in
23、to three cupels withthe silver proofs on two sides of the combined test samplebeads.9.11 Cupel to obtain dor beads by normal fire assaycupellation procedures.9.12 After cupellation, re-weigh the silver proofs on thebalance and record the weights.NOTE 4The loss of silver due to the original fire assa
24、y fusiontechnique is recovered by the slag recycling and re-fusion steps.10. Calculation10.1 Calculate the silver ratio as follows:Silver Ratio 5BA(1)where:A = initial weight of proof silver, mg, andB = final weight of proof silver, mg.10.2 Round the silver ratio to the nearest 0.0001 in accor-dance
25、 with Practice E 29.10.3 To correct a silver fire assay result, divide the weight ofthe silver in the test sample, determined by the difference inweight before and after parting, by the average silver ratio forthe two proofs to obtain the corrected silver weight.11. Keywords11.1 cupellation; fire as
26、say; silver; silver correction6Reagent Chemical, American Chemical Society Specifications, 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
27、 the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc., (USPC), Rockville,MD.TABLE 1 Slag Re-Fusion Fluxlitharge 55.4 gsodium carbonate 9.3 gsilica sand 9.4 gpotassium bitartrate 7.3 gborax 18.7 gE2296032ASTM International takes no position respecting the validit
28、y 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 any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject
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30、s. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If 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 i
31、s 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).E2296033
