1、Designation: E 2295 03Standard 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 immediately following the des
2、ignation 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 (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice covers the det
3、ermination 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 atomic absorp-tion spectrophotometry.1.2 The test methods appear in the following order:SectionsGravi
4、metric Method 10-11Atomic Absorption Method 12-131.3 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 and determine the applica-bility of re
5、gulatory limitations prior to use. (See Practices E 50and ISO Guide 35: 1989.)2. Referenced Documents2.1 ASTM Standards:D 1193 Specification for Reagent Water2E 29 Practice Using Significant Digits in Test Data toDetermine Conformance With Specifications3E 50 Practices for Apparatus, Reagents, and S
6、afety Precau-tions for Chemical Analysis of Metals4E 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related Materials4E 882 Guide for Accountability and Quality Control in theChemical Analysis Laboratory4E 1024 Guide for Chemical Analysis of Metals and MetalBearing Ores by Fla
7、me Atomic Absorption Spectropho-tometry4E 1335 Test Methods for Determination of Gold in Bullionby Cupellation42.2 Other Documents:ISO Guide 35-1989 Certification of Reference Materials-General and Statistical Principles5ISO 10378:1994 Copper Sulfide Concentrates-Determination of Gold and Silver Con
8、tents-Fire AssayGravimetric and Atomic Absorption SpectrometricMethod. Bugbee, Edward, Textbook of Fire Assaying;Smith, E.A., The Sampling and Assay of Precious Metals63. Terminology3.1 DefinitionsFor definitions of terms used in this Prac-tice, refer to Terminology E 135.4. Summary of Practice4.1 I
9、n the process of fire assay fusion slags and cupels arecollected, retreated and silver is determined in them to providea correction value for the fire assay determination of silver (seeGuide E 1024, Test Method E 1335, ISO 10378, Bugbee,Smith).5. Significance and Use5.1 These methods are primarily i
10、ntended to be used for thedetermination of silver correction in the fire assay silverdetermination. Silver assays are determined by fire assay forthe purpose of metallurgical exchange between seller andbuyer.5.2 It is assumed that all who use this method will be trainedanalysts capable of performing
11、 skillfully and safely. It isexpected 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 Balance, capable of weighing to 0.01 g.6.2 Analytical Balance, capable of weighing to 0.001
12、mg.6.3 Assay Furnace, capable of temperatures up to 1100C,accurate to 6 5C.6.4 Atomic Absorption Spectrophotometry, AAS.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
13、on Ores, Concentrates, and Related Metallurgical Materials .Current edition approved June 10, 2003. Published July 2003.2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 14.02.4Annual Book of ASTM Standards, Vol 03.055Bugbee, E. E., A Textbook of Fire Assaying, John Wiley
14、 and Sons, Inc., ThirdEd., 1946.6Smith, 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 Box C700, West Conshohocken, PA 19428-2959, United States.6.5 Ring Grinder, 250 g capacity.7. Reagents
15、 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 available.7Other grade
16、s 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 reagent water as definedby Type I of Specif
17、ication 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 Cupels, magnesite (MgCO3) or bone ash.7.7
18、Flour, common baking grade.7.8 Litharge, PbO-tech 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 E 50.8.2 All precautions and safe laboratory operating proce-dur
19、es should be followed when using perchloric acid.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 and cupels into a ring grinderand pulv
20、erize for about 20 s. This should reduce the material topass a No. 100 (150-m) sieve. This is the retreatment samplethat corresponds to the duplicate test sample.NOTE 1Longer grinding may cause caking of the ground material.Clean the ring grinder by grinding silica sand between each retreatmentsampl
21、e.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. FlourUsually4gaddor subtract to produce anapproxima
22、tely30 g lead fire assaybutton10.2 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 and flux together in thecrucibles.10
23、.4 Carry out the normal fire assay fusion and pour intoassay molds. Separate the slag from the lead button (SeeBugbee, Smith).10.5 Place the lead button from the retreatment fusion intoa new preheated cupel at 900C.10.6 Cupel to finish, (a lead free dor button should beformed).10.7 Discard the retre
24、atment 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 dor correction for each fusion as fol-lo
25、ws: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 29.11.3 To perform the dor correction
26、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 testsample.11.4 The gold must be determined i
27、n 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 assayprocedure, and weighing the resulting gold bead (see Test MethodE 1335). The sil
28、ver weight is determined by the difference between thedor and gold bead weights.ATOMIC APSORPTION SILVER CORRECTIONMETHOD12. 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 proced
29、ures.7Reagent 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 Pharma
30、copeiaand National Formulary, U.S. Pharmaceutical Convention, Inc., (USPC), Rockville,MD.E229503212.2 Add 5 mL of HCl and 15 mL of HClO4to theretreatment sample. Heat to perchloric acid fumes on a hotplate.NOTE 5Warning: A perchloric acid fume hood should be used for allperchloric acid digestions.12
31、.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 spectrophotometer at 328.1nm with a 10 cm path length burner head. Backg
32、roundcorrection must be used, (see Guide E 1024 and ISO Method10378). Perform three measurements on calibration solutions,that would match the low, middle, and high values of expectedmeasurements in g/mL Ag. Calculate, to three significantfigures the mean, absorbance for each calibration solution,pr
33、ovided the precision of values does not exceed 10 % relativestandard deviation (RSD). If this precision is exceeded, repeatthe calibration. Prepare a calibration curve.12.7 Read the blank and duplicate retreatment test solutionsin reference to the calibration curve (12.6) and record theresults g/mL
34、Ag.NOTE 6During AAS determinations, the retreatment and calibrationsolutions should have the same temperatures as well as the same acidconcentrations.NOTE 7The method of bracketing test solutions by calibration solu-tions to improve precision is recommended.NOTE 8Alternatively, an ICP atomic emissio
35、n 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 sampleg/g,C = concentration of silver in the retreatment analysissoluti
36、on, 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.13.3 Calculate the silver correction weight as follows:Silver Correction We
37、ight, 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 nearest 0.001mg and record.13.5 The silver correction weight is added to the milligramsof silver measured in the original fire ass
38、ay 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 connection with any item mentionedin this standard. Users of this standa
39、rd 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 responsible technical committee and must be reviewed every five years andif
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41、ch 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 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).E2295033
