1、Designation: E 2294 03 (Reapproved 2008)1Standard 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 ofo
2、riginal 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.1NOTEEditorial changes were made throughout in November 2008.1. Scope1.1
3、 This practice covers the determination of fire assaycorrection 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 doe
4、s 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 and determine the applica-bility of regulatory limitations prior to use. (See Test MethodsE 1335, Practices
5、E50, Guide E 882, and ISO Gu-ide 35: 1989.)2. Referenced Documents2.1 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
6、MaterialsE 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE 1335 Test Methods for Determination of Gold in Bullionby Fire Assay Cupellation Analysis2.2 Other Documents:3ISO Gu
7、ide 35: 1989 Certification of Reference Materials-General and Statistical 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 this
8、Prac-tice, refer to Terminology E 135.4. Summary of Practice4.1 In the process 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 E 1335,ISO 10378:
9、 1994, Bugbee,4and Smith5).5. Significance and Use5.1 This practice is primarily 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
10、use this practice will betrained analysts capable of performing skillfully and safely. Itis expected that work will be performed in a properly equippedlaboratory under appropriate quality control practices such asthose described in Guide E 882.6. Apparatus6.1 Analytical balanceCapable of weighing to
11、 0.001 mg.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 edition approved Nov. 1, 2008. Published D
12、ecember 2008. Originallyapproved in 2003. Last previous edition approved in 2003 as E 2294 03.2For 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
13、 Summary page onthe ASTM website.3Available 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, 1946.5Smit
14、h, E. A, The Sampling and Assay of the Precious Metals, Second Ed.,Charles Griffin and Co., Ltd., 1947.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.2 Assay furnaceCapable of temperatures up to 1100 C,accurate to 6 5 C.6.3 Hammer
15、Blacksmith type.6.4 Hammering blockFlat Steel 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 Chemi
16、cal 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 accuracy ofthe determination.7.2 Boraxsodium tetraborate(Na2B4O7)technicalgrade.7.3 Cupelsmagnesite (Mg
17、CO3) or bone ash.7.4 CruciblesStandard Fire 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, 99.9
18、9 % purity.7.11 Sodium Carbonate (Na2CO3)technical 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
19、 match the typical weight of the expected dor 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
20、 of sodium carbonate2. 14.5 g potassium carbonate3. 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
21、 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 assay is compared tothe original silver proof weight.10.
22、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 E29.10.3 To correct a silver fire assay result for test sam
23、ples,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 cupellation; fire assay; silver; silver correctionASTM International takes no p
24、osition 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 infringement of such rights, are entirely their own responsib
25、ility.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 or for additional standardsand should be addressed to
26、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 known to the ASTM Committee on Standards, at the addre
27、ss 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 ASTM at the aboveaddress or at 610-832-9585 (phone), 6
28、10-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC, http:/www.chemistry.org. For suggestions 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.E 2294 03 (2008)12
