1、Designation: E1568 13Standard Test Method forDetermination of Gold in Activated Carbon by Fire AssayGravimetry1This standard is issued under the fixed designation E1568; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of l
2、ast 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 test method covers the determination of gold inactivated carbon by fire assay collection and gravimetricmeasuremen
3、t. It covers the range of 15 g/g to 5000 g/g gold.1.2 The values stated in SI units are to be regarded as thestandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is therespons
4、ibility 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. For specific hazardsstatements, see Section 9 and 11.2.3-11.2.5, 11.3.4, and 11.3.4.2. Referenced Documents2.1 ASTM Standards:2D2862 Tes
5、t Method for Particle Size Distribution of Granu-lar Activated CarbonD2866 Test Method for Total Ash Content of ActivatedCarbonD2867 Test Methods for Moisture in Activated CarbonE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE50 Practices for Appara
6、tus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE173 Practice for Conducting Interlaboratory Studies ofMethods for Chemical Analysis of Metals (Withdrawn1998)3
7、E276 Test Method for Particle Size or ScreenAnalysis at No.4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores andRelated MaterialsE300 Practice for Sampling Industrial ChemicalsE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1601 Practice for Conducting an Interl
8、aboratory Study toEvaluate the Performance of an Analytical Method3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E135.4. Summary of Test Method4.1 The weighed test sample is ignited and fused with fireassay flux in a clay crucible. The lead metal
9、from the fusion isseparated and the precious metals concentrated by oxidationand adsorption of the lead on a cupel, the silver is parted withnitric acid, and the gold is annealed and weighed on amicrobalance.5. Significance and Use5.1 In the primary metallurgical processes used by themineral process
10、ing industry for gold bearing ores, gold isextracted with alkaline cyanide solutions and adsorbed ontoactivated carbon for recovery of the metal. Metallurgicalaccounting, process control, and ore evaluation procedures forthis type of mineral processing plant depend on accurate,precise, and prompt me
11、asurements of gold concentrations inthe activated carbon.5.2 This test method for gold in activated carbon is intendedprimarily as a referee method to test such materials for metalcontent. It is assumed that those who use these procedures willbe trained analysts capable of performing common laborato
12、ryprocedures skillfully and safely. It is expected that work will be1This test method is under the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and is the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgica
13、l Materials.Current edition approved April 1, 2013. Published June 2013. Originallyapproved in 1993. Last previous edition approved in 2008 as E1568 03 (2008)1.DOI: 10.1520/E1568-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.o
14、rg. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2
15、959. United States1performed in a properly equipped laboratory and that properwaste disposal procedures will be followed. Appropriate qual-ity control practices must be followed, such as those describedin Guide E882.6. Interferences6.1 Elements normally found in ore processing activatedcarbon do not
16、 interfere. When present, platinum group metalsmay be reported as gold in gravimetric fire assay determina-tions and must be less than 0.1 mg in the final gold bead.7. Apparatus7.1 Analytical Balance, capable of weighing to 0.1 g.7.2 Assay Mold, 100-mL capacity.7.3 Cupel, magnesite, 30-g lead capaci
17、ty.7.4 Drying Oven, having forced air circulation, with tem-perature control between 145 C and 155 C.7.5 Fire Clay Crucible, 30-g sample capacity.7.6 Hot Plate, having variable temperature control, usedwith ventilation control for acid fumes.7.7 Jewelers Rolls, capable of flattening dor beads.7.8 Mu
18、ffle Furnace, having air circulation with draftcontrols, capable of temperatures to 1100 C, accurate to 610 C, used with ventilation controls for lead fumes.7.9 Semi-Microbalance, capable of weighing to 0.01 mg.7.10 Roasting Dish, 15-g sample capacity.8. Reagents8.1 Purity of ReagentsReagent grade c
19、hemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascerta
20、ined that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.8.2 Ammonia Wash Solution, NH4OH (1 + 17)Add100 mL NH4OH to 1700 mL of water.8.3 BoraxNa2B4O7Sodium borate powder, with goldcontent less than 0.001 g/g.8.4 Fire Assay Flux Mixture
21、Mix 575 g of litharge (PbO)with 275 g of soda ash (Na2CO3), 75 g of borax (Na2B4O7),75 g of silica (SiO2), and 30 g of baking flour.8.5 Lead Foil99.9 % minimum, with gold content lessthan 0.001 g/g.8.6 PbOLead oxide powder, with gold content less than0.001 g/g.8.7 SiO2Silicon dioxide powder, with go
22、ld content lessthan 0.001 g/g.8.8 Silver Foil99.9 % minimum, with gold content lessthan 0.001 g/g.8.9 Na2CO3Sodium carbonate powder, with gold contentless than 0.001 g/g.8.10 Strong HNO3(1 + 2) Parting SolutionAdd 330 mLHNO3to 660 mL of water.8.11 Weak HNO3(1 + 4) Parting SolutionAdd 200 mLHNO3to 80
23、0 mL water.9. Hazards9.1 Refer to Practices E50 for precautions to be observed inthis test method.9.2 Use care when handling hot crucibles and operatingfurnaces in order to avoid personal injury by either burn orelectrical shock.9.3 Lead and PbO are toxic materials and are volatile atrelatively low
24、temperatures. Use accepted safety procedures toavoid inhalation, ingestion, or skin contact.9.4 Refer to WARNINGS in 11.2.3-11.2.5, 11.3.4, and11.3.4.10. Sampling10.1 Collect the sample in accordance with Practice E300.Samples must be free of any extraneous materials such as sand,rocks, and wood.10.
25、2 Sample PreparationDry the sample, in accordancewith the Oven-Drying Method of Test Methods D2867,toconstant weight at 150 C. If the analysis of a particularparticle size range is desired, separate fractions in accordancewith Test Method D2862.10.3 Test SamplePulverize the gross sample so that atle
26、ast 90 % passes a 150-m (No. 100 or 100 mesh, Tyler) sieve,in accordance with Test Method E276. Mix the gross sample.Weigh duplicate test samples of 15.0 g 6 1.0 g, and record thetest sample weights.11. Procedure11.1 Ignition:11.1.1 Spread5gofSiO2in the bottom of a preheatedroasting dish.11.1.2 Tran
27、sfer the test sample to the top of the silica bed inthe roasting dish.11.1.3 Ash at 650 C in a muffle furnace in accordance withTest Method D2866. Cool.11.2 Fusion:11.2.1 Transfer calcine and silica to a clay crucible contain-ing 50 g of fire assay flux.11.2.2 Cover with another 50 g portion of fire
28、 assay flux.Mix. Cover the mixture of5gofPbO.11.2.3 Place the crucible in a muffle furnace at 1050 C for1h.(WARNINGFire assay products produce toxic leadoxide fumes when heated. Use protective clothing, and workonly in well-ventilated areas.)4Reagent Chemicals, American Chemical Society Specificatio
29、ns, AmericanChemical Society, Washington, DC, www.chemistry.org. For suggestions on thetesting of reagents not listed by the American Chemical Society, see the UnitedStates Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention,Inc. (USPC), Rockville, MD, http:/www.usp.org.E1568 132NOTE
30、1Draft may be required for the first 15 min of fusion to preventboil-over.11.2.4 Remove the crucible from the muffle furnace andpour molten liquid into the assay mold carefully, makingcertain that all lead droplets are transferred to the mold.(WARNINGRapidly cooling slag may eject flying glass.Use e
31、ye protection and cover the slag immediately afterpouring.)11.2.5 After cooling, separate the lead metal from the slag.Form the lead metal into a cube using a hammer and metalplate. (WARNINGLead slag is toxic; use protective equip-ment and dispose of waste properly.)11.3 Cupellation:11.3.1 Preheat a
32、 cupel at 1000 C for 10 min in a mufflefurnace. Reduce the muffle furnace temperature controller to940 C.11.3.2 Place the lead buttons on the hot cupels and melt,without draft, as the temperature drops to 940 C (approxi-mately 5 min).11.3.3 Open the draft when the lead is melted, and continueheating
33、 with the draft open until the lead has been removed,leaving the dor bead in the cupel.NOTE 2A row of empty cupels should be placed in the front of themuffle furnace for temperature control of the draft.11.3.4 Vent the muffle furnace and remove the cupel fromthe furnace. Cool. (WARNINGHot cupels emi
34、t lead fumes.Use proper ventilation.)11.4 Inquartation:11.4.1 Carefully remove the dor bead from the cupel andweigh on the semimicrobalance to the nearest 0.01 mg. Recordthe dor weight. (WARNINGUsed cupels are toxic; useprotective equipment and dispose of waste properly.)11.4.2 Weigh the proper amou
35、nt of silver foil for the dorweight, according to Table 1, to the nearest 1 mg.11.4.3 Wrap the dor bead and silver foil in 10 g of lead foil.11.4.4 Repeat the cupellation procedure (11.3) with the foilpacket.11.5 Parting:11.5.1 Flatten the dor bead and place it in a 50-mLporcelain crucible.NOTE 3The
36、 use of jewelers rolls is recommended for flattening largedor beads.11.5.2 Anneal the bead in the crucible at 650 C in a mufflerfurnace or over a Bunsen burner.11.5.3 Place the crucible on a hot plate at 95 C and add 25mL of HNO3(1 + 4), preheated to 60 C 6 10 C. Heat for 30min.11.5.4 Carefully deca
37、nt spent parting solution and discard.11.5.5 Repeat the parting steps given in 11.5.3 and 11.5.4,using HNO3(1 + 2). Cool.11.5.6 Rinse with 25 mL of NH4OH (1 + 17) and five timeswith 25 mL water. Dry on a hot plate.11.5.7 Repeat the annealing step given in 11.5.2. Cool.11.6 GravimetryWeigh the gold b
38、ead to the nearest 0.01mg. Record the weight. If silver is detected visually in the goldbead, repeat the steps given in 11.4.3-11.5.7, reweigh, andrecord the weight.12. Calculation12.1 Calculate the g/g gold in the sample as follows:Gold, g/g 5 1000 A/B (1)where:A = gold measured, mg, andB = test sa
39、mple weight, g.12.2 Average the results from duplicate determinations, andround them to the nearest 1 g/g in accordance with PracticeE29.13. Precision and Bias513.1 PrecisionAn interlaboratory study was conducted inaccordance with Practice E173 to establish the within-laboratory and between-laborato
40、ry precision. Three materialswere tested by seven laboratories. The results are summarizedin Table 2.13.2 BiasNo information concerning the bias of this testmethod is available. However, the bias of the test method in asingle laboratory, or between laboratories, may be judged bythe deviation of the
41、mean value obtained using the test methodfrom the accepted value for a suitable reference material.NOTE 4The within-laboratory precision measures the maximumdifference expected in testing the material in a single laboratory at 95 %confidence. The between-laboratory precision measures the maximumdiff
42、erence expected in testing the material in more than one laboratory at95 % confidence.NOTE 5This test method has been evaluated in accordance withPractice E173. The Reproducibility R2of Practice E173 corresponds to theReproducibility Index R of Practice E1601. The Repeatability R1ofPractice E173 cor
43、responds to the Repeatability Index r of Practice E1601.14. Keywords14.1 activated carbon; fire assay gravimetry; gold content5Support data have been filed at ASTM International Headquarters. RequestRR:E01-1007.TABLE 1 Silver Additions for InquartationDor Weight Range,mgSilver Foil Weight Factor App
44、liedto the Dor Weight0.00 to 0.1 300.1to0.2 100.2to1.0 60.1 to 10.0 4 10.0 2.25TABLE 2 Interlaboratory PrecisionMaterialMeanAu, g/gR1; PracticeE173Au, g/gR2; PracticeE173Au, g/gStripped carbon 108.2 5.4 7.6Fine carbon 347.8 17.6 17.6Loaded carbon 3983 99.5 243E1568 133ASTM International takes no pos
45、ition 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 responsibil
46、ity.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 AS
47、TM 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 address
48、 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). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).E1568 134
