1、Designation:E229503(Reapproved 2008) 1 E229513 Standard Practice for Fire Assay Silver Corrections in Analysis of Metal Bearing Ores, Concentrates, and Related Metallurgical Materials by Silver Determination in Slags and Cupels 1 This standard is issued under the xed designation E2295; the number im
2、mediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval. e 1 NOTEEditor
3、ial and warning note changes were made throughout in December 2008. 1. Scope 1.1 This practice covers the determination of silver corrections for re assay of metal bearing ores, concentrates and related metallurgical materials using the spent slags and cupels from the re assay process, by gravimetry
4、 and atomic absorption spectrophotometry. 1.2 The test methods appear in the following order: Sections Gravimetric Method 1011 Atomic Absorption Method 1213 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standar
5、d does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. (See Practices E50 and ISOGuid
6、e35:1989.) 2. Referenced Documents 2.1 ASTM Standards: 2 D1193Specication for Reagent Water E29Practice for Using Signicant Digits in Test Data to Determine Conformance with Specications E50PracticesforApparatus,Reagents,andSafetyConsiderationsforChemicalAnalysisofMetals,Ores,andRelatedMaterials E13
7、5Terminology Relating to Analytical Chemistry for Metals, Ores, and Related Materials E882Guide for Accountability and Quality Control in the Chemical Analysis Laboratory E1024Guide for Chemical Analysis of Metals and Metal Bearing Ores by Flame Atomic Absorption Spectrophotometry (Withdrawn 2004) 3
8、 E1335Test Methods for Determination of Gold in Bullion by Fire Assay Cupellation Analysis 2.2 ISO Documents: 4 ISOGuide35:1989Certication of Reference MaterialsGeneral and Statistical Principles ISO10378:1994Copper Sulde ConcentratesDetermination of Gold and Silver ContentsFire Assay Gravimetric an
9、d Atomic Absorption Spectrometric Method 3. Terminology 3.1 DenitionsFor denitions of terms used in this practice, refer to Terminology E135. 1 This practice is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials and is the direct responsibili
10、ty of Subcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials. Current edition approved Dec. 15, 2008Nov. 1, 2013. Published January 2009December 2013. Originally approved in 2003. Last previous edition approved in 20032008 as E229503.E229503(Reapproved 2008) e1 . DOI: 10.1520
11、/E2295-03R08E01.10.1520/E2295-13. 2 ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatserviceastm.org.ForAnnualBookofASTMStandards volume information, refer to the standards Document Summary page on the ASTM website. 3 The last approved version of this histori
12、cal standard is referenced on www.astm.org. 4 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch. This document is not anASTM standard and is intended only to provide the user of anASTM sta
13、ndard an indication of what changes have been made to the previous version. Because it may not be technically possible to adequately depict all changes accurately,ASTM recommends that users consult prior editions as appropriate. In all cases only the current version of the standard as published by A
14、STM is to be considered the official document. Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States 14. Summary of Practice 4.1 In the process of re assay fusion slags and cupels are collected, retreated and silver is determined in them to
15、 provide a correction value for the re assay determination of silver (see Guide E1024,Test Methods E1335, ISO10378:1994, Bugbee, 5 and Smith 6 ). 5. Signicance and Use 5.1 These methods are primarily intended to be used for the determination of silver correction in the re assay silver determination.
16、 Silver assays are determined by re assay for the purpose of metallurgical exchange between seller and buyer. 5.2 Itisassumedthatallwhousethismethodwillbetrainedanalystscapableofperformingskillfullyandsafely.Itisexpected that work will be performed in a properly equipped laboratory under appropriate
17、 quality control practices such as those described in Guide E882. 6. Apparatus 6.1 Analytical Balance, capable of weighing to 0.01g. 6.2 Analytical Balance, capable of weighing to 0.001mg. 6.3 Assay Furnace, capable of temperatures up to 1100C, accurate to 65C. 6.4 Atomic Absorption Spectrophotometr
18、y, AAS. 6.5 Ring Grinder, 250g capacity. 7. Reagents and Materials 7.1 Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specications of the Committee on Analytical Reagents of the American Chemical Socie
19、ty where such specicationsareavailable. 7 Othergradesmaybeused,provideditisrstascertainedthatthereagentisofsufficientlyhighpurity to permit its use without lessening the accuracy of the determination. 7.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reag
20、ent water as dened by conforming to Type I or II of Specication D1193. Type III or IV may be used if they effect no measurable change in the blank or sample. 7.3 Borax, sodium tetraborate (Na 2 B 4 O 7 ), technical grade. 7.4 Ammonium Chloride Solution (NH 4 Cl 250g/L)Add 250g of ammonium chloride t
21、o 500mLof water in a 1-Lvolumetric ask. Dilute to the mark and mix. 7.5 Crucibles, standard re assay. 7.6 Cupels, magnesite (MgCO 3 ) or bone ash. 7.7 Flour, common baking grade. 7.8 Litharge (PbO),technical grade, silver free. 7.9 Silica Sand (SiO 2 ),technical grade. 7.10 Sodium Carbonate (Na 2 CO
22、 3 ),technical grade. 8. Hazards 8.1 For precautions to be observed in this practice, refer to Practice E50. 8.2 All precautions and safe laboratory operating procedures should be followed when using HClO 4 . 9. Sampling and Sample Preparation 9.1 Weigh the re assay slags and cupels (7.6) from the d
23、uplicate fusion and cupellation processes for each test sample on a balance to 0.01g. Record weight. 9.2 Place the weighed slags and cupels (7.6) into a ring grinder and pulverize for about 20 s. This should reduce the material to pass a 150-m sieve. This is the retreatment sample that corresponds t
24、o the duplicate test sample. NOTE 1Longer grinding may cause caking of the ground material. Clean the ring grinder by grinding silica sand between each retreatment sample. 5 Bugbee, E. E., A Textbook of Fire Assaying, Third Ed., John Wiley and Sons, Inc., Hoboken, NJ, 1946. 6 Smith, E. A, The Sampli
25、ng and Assay of the Precious Metals, Second Ed., Charles Griffin and Co., Ltd., 1947. 7 Reagent Chemicals, American Chemical Society Specications, American Chemical Society, Washington, DC, http:/www.chemistry.org. DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Soc
26、iety, seeAnnual Standards 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. MD. E229513 2GRAVIMETRIC SILVER CORRECTION METHOD 10. Procedure 10.1 To
27、the duplicate crucibles saved from the re assay fusion of each test sample, add the following ux. Crucible Fire Assay Flux 1. Litharge50 g (7.8) 2. Sodium Carbonate50 g (7.10) 3. Silica50 g (7.9) 4. Borax50 g (7.3) 5. FlourUsually 4 g add or subtract to produce an approximately 30 g lead re assay bu
28、tton (7.7) 10.2 Weigh two portions of the retreatment sample into the pre-uxed crucibles and record the weights.masses. Sample A = 14.583 g or 1 2 AT Sample B = 29.167 g or 1 AT NOTE 2AT=Assay Ton, a re assay weightmass system. 10.3 Mix retreatment samples and ux together in the crucibles. 10.4 Carr
29、y out the normal re assay fusion and pour into assay molds. Separate the slag from the lead button (see Bugbee 5 and Smith 6 ). 10.5 Place the lead button from the retreatment fusion into a new preheated cupel at 900C. 10.6 Cupel to nish (a lead free dor buttonbead should be formed). 10.7 Discard th
30、e retreatment samples and crucibles when analysis and correction is completed. NOTE 3These materials contain lead wastes; dispose of properly. 10.8 Weigh the duplicate retreatment dor beads to the nearest 0.001mg and record the weights.masses. 11. Calculation 11.1 Calculate the dor correction for ea
31、ch fusion as follows: Dore Correction,mg5 AB C (1) where: A = total slags and cupels weight, g, B = dor bead weight from retreatment fusion, mg, and C = weight of retreatment sample used in the fusion, g. A = total slags and cupels mass, g, B = dor bead mass from retreatment fusion, mg, and C = mass
32、 of retreatment sample used in the fusion, g. 11.2 Round the dor correction to the nearest 0.001mg in accordance with Practice E29. 11.3 To perform the dor correction on the original re assay, add the average of the two dor corrections to the individual uncorrected dor weightsmasses for the re assay
33、s of the test sample. The combined weightmass is then the corrected dor weightmass for nal calculation of the gold plus silver in the test sample. 11.4 The gold must be determined in all dor beads and subtracted from each dor weightmass to obtain the silver weightmass in that dor bead. NOTE 4Gold ca
34、n also be determined by rst weighing the dor, dor bead, parting the dor bead with nitric acid according to standard re assay procedure,andweighingtheresultinggoldbead(seeTestMethodsE1335).Thesilverweightmassisdeterminedbythedifferencebetweenthedorbead and gold bead weights.masses. ATOMICABSORPTION S
35、ILVER CORRECTION METHOD 12. Procedure 12.1 Transfer duplicate 2.00 g portions of the retreatment sample (9.2) into 400-mL beakers and record the weights.masses. Carry a blank beaker throughout the digestion procedures. 12.2 Add 5mL of HCl and 15mL of HClO 4 to the retreatment sample. Heat to HClO 4
36、fumes on a hot plate. (WarningAn HClO 4 fume hood should be used for all HClO 4 digestions.) 12.3 Cool. When cool to touch, add 40mL HCl and 5mL of NH 4 Cl (7.4) solution. 12.4 Mix solution, then place into a 400-mL volumetric ask. E229513 312.5 Dilute to volume with water. Mix. This is the analysis
37、 solution. 12.6 Set the atomic absorption spectrophotometer at 328.1nm with a 10cm path length burner head. Background correction must be used, (see Guide E1024 and ISO10378:1994). Perform three measurements on calibration solutions, that would match the low, middle, and high values of expected meas
38、urements in g/mL silver. Calculate, to three signicant gures the mean, absorbanceforeachcalibrationsolution,providedtheprecisionofvaluesdoesnotexceed10%relativestandarddeviation(RSD). If this precision is exceeded, repeat the calibration. Prepare a calibration curve. 12.7 Read the blank and duplicat
39、e retreatment test solutions in reference to the calibration curve (12.6) and record the results g/mL silver. NOTE 5During AAS determinations, the retreatment and calibration solutions should have the same temperatures as well as the same acid concentrations. NOTE 6The method of bracketing test solu
40、tions by calibration solutions to improve precision is recommended. NOTE 7Alternatively, an ICP atomic emission spectrometer can be used for the determination of silver at: 328.1 nm. 13. Calculations 13.1 Calculate the silver content of the retreatment sample as follows: D5C2B!400/W (2) where: D = c
41、oncentration of silver in the retreatment sample, g/g, C = concentration of silver in the retreatment analysis solution, g/mL, B = concentration of silver in the blank solution, g/mL, 400 = volume of the retreatment analysis solution, mL, and W = weight of the retreatment sample, g. W = mass of the
42、retreatment sample, g. 13.2 Average the results for the duplicate retreatment samples. 13.3 Calculate the silver correction weightmass as follows: SilverCorrectionWeight,mg5 AD 1000 (3) SilverCorrectionMass,mg5 AD 1000 (3) where: A = total slag and cupel weight, g, and A = total slag and cupel mass,
43、 g, and D = concentration of silver in the retreatment sample, g/g. 13.4 Round the silver correction weightmass to the nearest 0.001mg and record. 13.5 The silver correction weightmass is added to the milligrams of silver measured in the original re assay silver determination to obtain the corrected
44、 silver re assay. 14. Keywords 14.1 cupellation; re assay; silver; silver correction ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentioned in this standard. Users of this standard are expressly advised that determination of t
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