1、Designation: E 2295 03 (Reapproved 2008)1Standard Practice forFire Assay Silver Corrections in Analysis of Metal BearingOres, Concentrates, and Related Metallurgical Materials bySilver Determination in Slags and Cupels1This standard is issued under the fixed designation E 2295; the number immediatel
2、y following the designation indicates 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 () indicates an editorial change since the last revision or reapproval.1NOTEEditorial and war
3、ning note changes were made throughout in December 2008.1. Scope1.1 This practice covers the determination of silver correc-tions for fire assay of metal bearing ores, concentrates andrelated metallurgical materials using the spent slags and cupelsfrom the fire assay process, by gravimetry and atomi
4、c absorp-tion spectrophotometry.1.2 The test methods appear in the following order:SectionsGravimetric Method 1011Atomic Absorption Method 12131.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard does not purpor
5、t 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 Practices E50and ISO Guide 35:1989.)2. Ref
6、erenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE29 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 MaterialsE
7、135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE 1024 Guide for Chemical Analysis of Metals and MetalBearing Ores by Flame Atomic Absorption Spectropho-tometry3E 1335 Test Met
8、hods for Determination of Gold in Bullionby Fire Assay Cupellation Analysis2.2 ISO Documents:4ISO Guide 35:1989 Certification of Reference MaterialsGeneral and Statistical PrinciplesISO 10378:1994 Copper Sulfide ConcentratesDetermination of Gold and Silver ContentsFire AssayGravimetric and Atomic Ab
9、sorption SpectrometricMethod3. 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 slags and cupels arecollected, retreated and silver is determined in them to providea correction value fo
10、r the fire assay determination of silver (seeGuide E 1024, Test Methods E 1335, ISO 10378:1994, Bug-bee,5and Smith6).5. Significance and Use5.1 These methods are primarily intended to be used for thedetermination of silver correction in the fire assay silverdetermination. Silver assays are determine
11、d by fire assay forthe purpose of metallurgical exchange between seller andbuyer.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 Met
12、allurgical Materials.Current edition approved Dec. 15, 2008. Published January 2009. Originallyapproved in 2003. Last previous edition approved in 2003 as E 2295 03.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Bo
13、ok of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.4Available from International Organization for Standardization (ISO), 1, ch. dela Voie-Creuse, Case p
14、ostale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.5Bugbee, E. E., A Textbook of Fire Assaying, Third Ed., John Wiley and Sons,Inc., Hoboken, NJ, 1946.6Smith, E. A, The Sampling and Assay of the Precious Metals, Second Ed.,Charles Griffin and Co., Ltd., 1947.1Copyright ASTM International,
15、100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.2 It is assumed that all who use this method will be trainedanalysts capable of performing skillfully and safely. It isexpected that work will be performed in a properly equippedlaboratory under appropriate quality
16、 control practices such asthose described in Guide E 882.6. Apparatus6.1 Analytical Balance, capable of weighing to 0.01 g.6.2 Analytical Balance, capable of weighing to 0.001 mg.6.3 Assay Furnace, capable of temperatures up to 1100 C,accurate to 6 5 C.6.4 Atomic Absorption Spectrophotometry, AAS.6.
17、5 Ring Grinder, 250 g capacity.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
18、 specifications are available.7Other 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 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean r
19、eagent water as definedby Type I of Specification D 1193.7.3 Borax, sodium tetraborate (Na2B4O7), technical grade.7.4 Ammonium Chloride Solution (NH4Cl 250g/L)Add250 g of ammonium chloride to 500 mL of water in a 1-Lvolumetric flask. Dilute to the mark and mix.7.5 Crucibles, standard fire assay.7.6
20、Cupels, magnesite (MgCO3) or bone ash.7.7 Flour, common baking grade.7.8 Litharge (PbO), technical grade, silver free.7.9 Silica Sand (SiO2), technical grade.7.10 Sodium Carbonate (Na2CO3), technical grade.8. Hazards8.1 For precautions to be observed in this practice, refer toPractice E50.8.2 All pr
21、ecautions and safe laboratory operating proce-dures should be followed when using HClO4.9. Sampling and Sample Preparation9.1 Weigh the fire assay slags and cupels from the duplicatefusion and cupellation processes for each test sample on abalance to 0.01 g. Record weight.9.2 Place the weighed slags
22、 and cupels into a ring grinderand pulverize for about 20 s. This should reduce the materialto pass a 150-m sieve. This is the retreatment sample thatcorresponds to the duplicate test sample.NOTE 1Longer grinding may cause caking of the ground material.Clean the ring grinder by grinding silica sand
23、between each retreatmentsample.GRAVIMETRIC SILVER CORRECTION METHOD10. Procedure10.1 To the duplicate crucibles saved from the fire assayfusion of each test sample, add the following flux.Crucible Fire Assay Flux1. Litharge50 g2. Sodium Carbonate50 g3. Silica50 g4. Borax50 g5. FlourUsually 4 g add o
24、r subtract to produce an approximately30 g lead fire assay button10.2 Weigh two portions of the retreatment sample into thepre-fluxed crucibles and record the weights.Sample A = 14.583 g or12 ATSample B = 29.167 g or 1 ATNOTE 2AT = Assay Ton, a fire assay weight system.10.3 Mix retreatment samples a
25、nd flux together in thecrucibles.10.4 Carry out the normal fire assay fusion and pour intoassay molds. Separate the slag from the lead button (seeBugbee5and Smith6).10.5 Place the lead button from the retreatment fusion intoa new preheated cupel at 900 C.10.6 Cupel to finish (a lead free dor button
26、should beformed).10.7 Discard the retreatment samples and crucibles whenanalysis and correction is completed.NOTE 3These materials contain lead wastes; dispose of properly.10.8 Weigh the duplicate retreatment dor beads to thenearest 0.001 mg and record the weights.11. Calculation11.1 Calculate the d
27、or correction for each fusion as fol-lows:Dor Correction, mg 5ABC(1)where:A = total slags and cupels weight, g,B = dor bead weight from retreatment fusion, mg, andC = weight of retreatment sample used in the fusion, g.11.2 Round the dor correction to the nearest 0.001 mg inaccordance with Practice E
28、29.11.3 To perform the dor correction on the original fireassay, add the average of the two dor corrections to theindividual uncorrected dor weights for the fire assays of thetest sample. The combined weight is then the corrected dorweight for final calculation of the gold plus silver in the testsam
29、ple.11.4 The gold must be determined in all dor beads andsubtracted from each dor weight to obtain the silver weight inthat dor bead.NOTE 4Gold can also be determined by first weighing the dor,parting the dor with nitric acid according to standard fire assay7Reagent Chemicals, American Chemical Soci
30、ety 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 Na
31、tional Formulary, U.S.Pharmacopeial Convention, Inc. (USPC), Rockville, MD, http:/www.usp.org.E 2295 03 (2008)12procedure, and weighing the resulting gold bead (see Test MethodsE 1335). The silver weight is determined by the difference between thedor and gold bead weights.ATOMIC ABSORPTION SILVER CO
32、RRECTIONMETHOD12. Procedure12.1 Transfer duplicate 2.00 g portions of the retreatmentsample (9.2) into 400-mL beakers and record the weights.Carry a blank beaker throughout the digestion procedures.12.2 Add 5 mL of HCl and 15 mL of HClO4to the retreat-ment sample. Heat to HClO4fumes on a hot plate.(
33、WarningAn HClO4fume hood should be used for allHClO4digestions.)12.3 Cool. When cool to touch, add 40 mL HCl and 5 mL ofNH4Cl solution.12.4 Mix solution, then place into a 400-mL volumetricflask.12.5 Dilute to volume with water. Mix. This is the analysissolution.12.6 Set the atomic absorption spectr
34、ophotometer at328.1 nm with a 10 cm path length burner head. Backgroundcorrection must be used, (see Guide E 1024 andISO 10378:1994). Perform three measurements on calibrationsolutions, that would match the low, middle, and high values ofexpected measurements in g/mL silver. Calculate, to threesigni
35、ficant figures the mean, absorbance for each calibrationsolution, provided the precision of values does not exceed10 % relative standard deviation (RSD). If this precision isexceeded, repeat the calibration. Prepare a calibration curve.12.7 Read the blank and duplicate retreatment test solutionsin r
36、eference to the calibration curve (12.6) and record theresults g/mL silver.NOTE 5During AAS determinations, the retreatment and calibrationsolutions should have the same temperatures as well as the same acidconcentrations.NOTE 6The method of bracketing test solutions by calibration solu-tions to imp
37、rove precision is recommended.NOTE 7Alternatively, an ICP atomic emission spectrometer can beused for the determination of silver at: 328.1 nm.13. Calculations13.1 Calculate the silver content of the retreatment sampleas follows:D 5 C 2 B!400/W (2)where:D = concentration of silver in the retreatment
38、 sample,g/g,C = concentration of silver in the retreatment analysissolution, g/mL,B = concentration of silver in the blank solution, g/mL,400 = volume of the retreatment analysis solution, mL, andW = weight of the retreatment sample, g.13.2 Average the results for the duplicate retreatmentsamples.13
39、.3 Calculate the silver correction weight as follows:Silver Correction Weight, mg 5AD1000(3)where:A = total slag and cupel weight, g, andD = concentration of silver in the retreatment sample, g/g.13.4 Round the silver correction weight to the nearest0.001 mg and record.13.5 The silver correction wei
40、ght is added to the milligramsof silver measured in the original fire assay silver determina-tion to obtain the corrected silver fire assay.14. Keywords14.1 cupellation; fire assay; silver; silver correctionASTM International takes no position respecting the validity of any patent rights asserted in
41、 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 at any time by the re
42、sponsible 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 comments will receive care
43、ful 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 by ASTM Internationa
44、l, 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).E 2295 03 (2008)13
