1、Designation: E2294 03 (Reapproved 2013)Standard Practice forProof Silver Corrections in Metal Bearing Ores,Concentrates, and Related Materials by Fire AssayGravimetry1This standard is issued under the fixed designation E2294; the number immediately following the designation indicates the year oforig
2、inal adoption or, in the case of revision, 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 practice covers the determination of fire assaycorrection
3、for silver, utilizing proof silver, ores, concentrates,and related metallurgical materials.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, asso
4、ciated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. (See Test MethodsE1335, Practices E50, Guide E882, and ISO Guide 35: 1989.)2. Referenced Documents2
5、.1 ASTM Standards:2E29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetal
6、s, Ores, and Related MaterialsE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1335 Test Methods for Determination of Gold in Bullionby Fire Assay Cupellation Analysis2.2 Other Documents:3ISO Guide 35: 1989 Certification of Reference Materials-General and Statisti
7、cal PrinciplesISO 10378: 1994 Copper Sulfide ConcentratesDetermina-tion of Gold and Silver ContentsFire Assay Gravimetricand Atomic Absorption Spectrometric Method3. Terminology3.1 DefinitionsFor definitions of terms used in thisPractice, refer to Terminology E135.4. Summary of Practice4.1 In the pr
8、ocess of fire assay, silver losses occur. Proofsilver is carried through the assay fusion and cupellationprocedures to determine losses that can provide the fire assaysilver correction values (see Test Methods E1335,ISO 10378: 1994, Bugbee,4and Smith5).5. Significance and Use5.1 This practice is pri
9、marily intended to be used for thecorrection of silver loss in the 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
10、 and safely. Itis expected that work will be performed in a properly equippedlaboratory under appropriate quality control practices such asthose described in Guide E882.6. Apparatus6.1 Analytical balanceCapable of weighing to 0.001 mg.1This practice is under the jurisdiction of ASTM Committee E01 on
11、 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 Nov. 1, 2013. Published December 2013. Originallyapproved in 2003. Last previous edition approved in
12、 2008 as E2294 03 (2008)1.DOI: 10.1520/E2294-03R13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available
13、 from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.4Bugbee, E. E., A Textbook of Fire Assaying, Third Ed., John Wiley and Sons,Inc., Hoboken, NJ, 1946.5Smith, E. A, The Sampling and Assay of the Prec
14、ious Metals, Second Ed.,Charles Griffin and Co., Ltd., 1947.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.2 Assay furnaceCapable of temperatures up to 1100 C,accurate to 6 5 C.6.3 HammerBlacksmith type.6.4 Hammering blockFlat Stee
15、l plate.7. 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 wheresuch specifications are ava
16、ilable.6Other 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 Boraxsodium tetraborate(Na2B4O7)technicalgrade.7.3 Cupelsmagnesite (MgCO3) or bone ash.7.4 CruciblesStandard Fire
17、Assay clay.7.5 Flourcommon baking grade.7.6 Lead Foil, 99.99 % purity, min (1 ug/g silver max).7.7 Litharge (PbO)technical gradeprecious metal free.7.8 Potassium Carbonate (K2CO3)technical grade.7.9 Silica Sand (SiO2)technical grade.7.10 Silver Metal, 99.99 % purity.7.11 Sodium Carbonate (Na2CO3)tec
18、hnical grade.8. Hazards8.1 For precautions to be observed in this practice, refer toPractices E50.9. Procedure9.1 Prepare samples according to normal fire assay proce-dures (Bugbee4or Smith5).9.2 Weigh two proof silver samples (99.99 % pure silverfoil), to match the typical weight of the expected do
19、r bead. Ifthe weight of the dor bead is unknown, weigh two proof silversamples, approximately 75 mg to 150 mg and 250 mg to350 mg.9.3 Fill an assay clay crucible with the same flux used in thetest samples. A typical flux is:Typical Fire Assay Flux1. 30.5 g of sodium carbonate2. 14.5 g potassium carb
20、onate3. 6.5 g silica sand4. 4 g to 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 samples and lead foil packeton the top of the mixture, then cover with the flux cap mixture.9.5 Place c
21、rucibles 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 assay is compared tothe original silver proof weight.10. Calculation10.1 Calculate the silver ratio a
22、s 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 E29.10.3 To correct a silver fire assay result for test samples,divide the weight of the silver in the
23、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 cupellation; fire assay; silver; silver correctionASTM International takes no position respecting the validity of any paten
24、t 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 to revision a
25、t 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 or for additional standardsand should be addressed to ASTM International Headquarters. Your commen
26、ts 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 is copyrighted
27、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-mai
28、l); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC, http:/www.chemistry.org. For suggesti
29、ons onthe testing of reagents not listed by the American Chemical Society, see AnnualStandards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., http:/, and the United States Pharmacopeia and National Formulary, U.S.Pharmacopeial Convention, Inc. (USPC), Rockville, MD, http:/www.usp.org.E2294 03 (2013)2
