1、Designation: E 2294 03Standard Practice forProof Silver Corrections in Metal Bearing Ores,Concentrates and Related Materials by Fire AssayGravimetry1This standard is issued under the fixed designation E 2294; the number immediately following the designation indicates the year oforiginal adoption or,
2、 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 standard practice covers the determination of fireassay correction for sil
3、ver, utilizing proof silver, for ores,concentrates and related metallurgical 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 user of this standard to establish appro-priate safety and health practices
4、and determine the applica-bility of regulatory limitations prior to use. (See MethodE 1335, Practices E 50, Guide E 882, and ISO Guide 35).2. Referenced Documents2.1 ASTM Standards:E 29 Practice for Using Significant Digits in Test Data toDetermine Conformance With Specifications2E 50 Standard Pract
5、ices for Apparatus, Reagents, andSafety Precautions for Chemical Analysis of Metals3E 135 Standard Terminology relating to Analytical Chem-istry for Metals, Ores, and Related Materials2E 882 Guide for Accountability and Quality Control in theChemical Analysis of Metals2E 1335 Test Methods for Determ
6、ination of Gold in Bullionby Cupellation22.2 Other DocumentsISO Guide 35: 1989, Certification of Reference Materials-General and Statistical PrinciplesISO 10378:1994, Copper Sulfide Concentrates- Determina-tion of Gold and Silver Contents- Fire Assay Gravimetricand Atomic Absorption Spectrometric Me
7、thodBugbee, Edward, Textbook of Fire Assaying4Smith, E.A., 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, silver losses occur. Proofsilver is ca
8、rried through the assay fusion and cupellationprocedures to determine losses that can provide the fire assaysilver correction values, (see Method E 1335, Method ISO10378, Bugbee, , Smith).5. Significance and Use5.1 This practice is primarily intended to be used for thecorrection of silver loss in th
9、e fire assay process. Silver assaysare determined by fire assay for the purpose of metallurgicalexchange between seller and buyer.5.2 It is assumed that all who use this practice will betrained analysts capable of performing skillfully and safely. Itis expected that work will be performed in a prope
10、rly equippedlaboratory under appropriate quality control practices such asthose described in Guide E 882.6. Apparatus6.1 Analytical balanceCapable of weighing to 0.001 mg6.2 Assay furnaceCapable of temperatures up to 1100 C,accurate to 65C6.3 HammerBlacksmith type6.4 Hammering blockFlat Steel plate7
11、. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society where1This practice is under the jurisdic
12、tion 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 edition approved June 10, 2003. Published July 2003.2Annual Book of ASTM Standards, Vol
13、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 Griffinand Co., Ltd., Second Ed., 1947.1Copyright ASTM International, 100 Barr Harbor Drive, PO
14、 Box C700, West Conshohocken, PA 19428-2959, United States.such specifications are available6. Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.7.2 Borax- sodium tetraborate-
15、(Na2B4O7) - technical grade.7.3 Cupels- magnesite (MgCO3) or bone ash7.4 Crucibles- Standard Fire Assay clay7.5 Flour- common baking grade7.6 Lead Foil, 99.99 % purity, min (1 ug/g silver max).7.7 Litharge (PbO) - technical grade- precious metal free7.8 Potassium Carbonate (K2CO3) - technical grade7
16、.9 Silica Sand (SiO2) - technical grade7.10 Silver metal, 99.99 % purity7.11 Sodium Carbonate- (Na2CO3) - technical grade8. Hazards8.1 For precautions to be observed in this practice, refer toPractice E 50.9. Procedure9.1 Prepare samples according to normal fire assay proce-dures, (Bugbee, , or Smit
17、h).9.2 Weigh two proof silver samples (99.99 % pure silverfoil), to match the typical weight of the expected dore bead. Ifthe weight of the dore bead is unknown, weigh two proofsilver samples, approximately 75-150 mg and 250-350 mg.9.3 Fill an assay clay crucible with the same flux used in thetest s
18、amples. A typical flux is:Typical Fire Assay Flux1. 30.5 g of sodium carbonate2. 14.5 g potassium carbonate3. 6.5 g silica sand4. 4-5 g flour5. 60 g litharge6. flux cap, (15 g litharge and 3 g borax)9.4 Mix the flux mixture first. For the best and consistentresults, transfer the weighed silver sampl
19、es and lead foil packeton the top of the mixture, then cover with the flux cap mixture.9.5 Place crucibles in fire assay furnace and proceed withfusion and cupellation steps required for test samples.9.6 After cupellation, the silver proof is weighed on themicrobalance. The weight after the fire ass
20、ay is compared tothe original silver proof weight.10. Calculation10.1 Calculate the silver ratio as follows:Silver Ratio 5 B/A (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 with Practice E 29.
21、10.3 To correct a silver fire assay result for test samples,divide the weight of the silver in the test sample, determined bythe difference in weight before and after parting, by the averagesilver ratio for the two proofs to obtain the corrected silverweight.11. Keywords11.1 Silver; silver correctio
22、n; fire assay; cupellationASTM 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 advised that determination of the validity of any such patent rights, and the riskof infrin
23、gement 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 reapproved or withdrawn. Your comments are invited either for revision of this standard
24、 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 you feel that your comments have not received a fair hearing you shouldmake your views
25、 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
26、 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).6Reagent 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 the United States Pharmacopeiaand National Formulary, U.S. Pharmaceutical Convention, Inc., (USPC), Rockville,MD.E2294032
