1、Designation: E1805 13Standard Test Method forDetermination of Gold in Copper Concentrates by FireAssay Gravimetry1This standard is issued under the fixed designation E1805; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last 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 is for the determination of gold incopper concentrates in the content range from 0.2 g/g to 17g/g.N
3、OTE 1The lower scope limit is set in accordance with PracticeE1601.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It
4、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. For specificwarning statements, see 11.3.1, 11.5.4, and 11.6.5.2. Referenced Documents2.1 ASTM Standards:2D1193 Specificati
5、on 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 MaterialsE135 Terminology Relating to Analytical Chemistry forMeta
6、ls, Ores, and Related MaterialsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an A
7、nalytical Method3. Terminology3.1 For definitions of terms used in this test method, refer toTerminology E135.4. Summary of Test Method4.1 A test sample of copper concentrate is fluxed and fusedin a clay crucible. The precious metals are reduced, collected ina lead button, and then cupelled to remov
8、e the lead. Theremaining dor bead is parted with nitric acid to remove thesilver and other impurities from the gold. The gold is thenannealed, cleaned, and weighed on a microbalance.5. Significance and Use5.1 In the metallurgical process used in the miningindustries, gold is often carried along with
9、 copper during theflotation concentration process. Metallurgical accounting, pro-cess control, and concentrate evaluation procedures for thistype of material depend on an accurate, precise measurementof the gold in the copper concentrate. This test method isintended to be a reference method for meta
10、llurgical laborato-ries and a referee method to settle disputes in commercialtransactions. It is also a definitive method intended to testmaterials for compliance with compliance with compositionalspecifications and to provide data for certification of referencematerials. It is essential that each p
11、erformance of the methodbe validated by applying it to appropriate reference materials atthe same time and in the same manner as it is applied to theunknowns.5.2 It is assumed that all who use this test method will betrained analysts capable of performing skillfully and safely. Itis expected that th
12、e work will be performed in a properlyequipped laboratory under appropriate quality control practicessuch as those described in Guide E882.6. Interferences6.1 Elements normally found in copper concentrates withinthe limits of 1.1 do not interfere. High concentrations ofarsenic, antimony, tellurium,
13、bismuth, nickel, and platinumgroup metals (and, in some instances, copper), however, mayinterfere with the fusion and cupellation steps.1This test method is under the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and is the directresponsibility of
14、Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edition approved April 1, 2013. Published June 2013. Originallyapproved in 1996. Last previous edition approved in 2007 as E1805 - 07. DOI:10.1520/E1805-13.2For referenced ASTM standards, visit the ASTM website,
15、www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17.
16、Apparatus7.1 Analytical Balance, capable of weighing to 0.1 g.7.2 Assay Mold, 100-mL capacity.7.3 Cube or Cone Mixer, 1000-g capacity.7.4 Cupel, magnesite or bone ash, 40-g lead capacity.7.5 Drying Oven, forced air circulation with temperaturecontrol, 104 C.7.6 Fire Assay Bead Brush.7.7 Fire Assay B
17、ead Pliers.7.8 Fire Assay Clay Crucible, 20-g to 30-g sample capacity.7.9 Fire Assay Muffle Furnace, gas-fired or electric,equipped with air circulation systems and with draft controls,capable of temperatures to 1100 C 6 10 C, and withventilation controls for acid and lead fumes.7.10 Fire Assay Tong
18、s, crucible and cupel.7.11 Fire Assay Tumble Mixeran industrial mixer-crucibletumbler.7.12 Hot Plate, with variable temperature control and ven-tilation controls for acid fumes.7.13 Jaw Crusher, capable of reducing cupels and slag topass a 4-mm sieve.7.14 Ring Pulverizer, capable of 250-g minimal ca
19、pacity.7.15 Semi-Microbalance, capable of weighing to 0.001 mg.7.16 Steel Hammer.8. Reagents and Materials8.1 Borax Glass (Na2B4O7).8.2 Cupel Correction FluxBlend the following ingredi-ents in the listed proportions:Borax Glass 15 gFlour 2 gLead Oxide 30 gPotassium Carbonate 45 gSilica 12 g8.3 Fire
20、Assay Flux MixtureBlend the following ingredi-ents in the listed proportions:Borax Glass 15 gLead Oxide 55 gPotassium Carbonate 6 gPotassium Nitrate 13 gSilica 6 gSodium Carbonate 20 gNOTE 2Perform a preliminary fusion to determine lead button weight.If a 30-g to 40-g lead button is not obtained, ad
21、just the amount of KNO3and try again. Increasing the KNO3produces a smaller lead button, anddecreasing the KNO3produces a larger one.8.4 Flour, ground wheat.8.5 Lead Oxide, Litharge, (PbO)Containing less than 0.02g/g gold and less than 0.40 g/g silver.8.6 Potassium Carbonate, Potash (K2CO3).8.7 Pota
22、ssium Nitrate, Niter (KNO3).8.8 Silica (SiO2), 95 % minimum purity, particle size lessthan 180 m.8.9 Silver Foil, 99.9 % purity with less than 0.10 g/g goldcontent.8.10 Silver Solution (1 g/L)Add 1.557 g silver nitrate to1000 mL of water containing 5 mL of HNO3, mix. Store in adark bottle.8.11 Sodiu
23、m Carbonate, Soda Ash (Na2CO3), anhydroustechnical grade.8.12 Sodium Chloride, salt (NaCl).8.13 Purity of ReagentsUse reagent grade chemicals in alltests. Unless otherwise indicated, all reagents conform to thespecifications of the Committee on Analytical Reagents of theAmerican Chemical Society whe
24、re such specifications areavailable. Other grades may be used provided it is firstascertained that the reagents are of sufficiently high purity topermit their use without lessening the accuracy of the deter-mination.38.14 Purity of WaterUnless otherwise indicated, refer-ences to water shall be under
25、stood to mean reagent water asdefined by Type I or II of Specification D1193. Type III or IVmay be used if they effect no measurable change in the blankor sample.9. Hazards9.1 For precautions to be observed in the use of certainreagents in this test method, refer to Practice E50.9.2 See specific war
26、nings in 11.3.1, 11.5.4, 11.6.5.10. Sampling and Sample Preparation10.1 Collect, store, and handle gross samples in accordancewith the safety and materials guidelines in Practice E50. Grosssamples must be free of all extraneous materials.10.2 Dry the laboratory sample to constant weight at104 C.NOTE
27、 3If the gross sample was dried at a low temperature (e.g. 60 Cfor mercury) take the low temperature portion(s) and a separate moisturesample, prior to drying at 104 C.10.3 Grind the laboratory sample in a ring mill so that100 % passes through a 150-m sieve and blend the preparedsample in a cube or
28、cone blender, if necessary to further reducethe heterogeneity of the laboratory sample. Obtain the testsamples by incremental division by mixing the preparedsample and spreading it on a flat non moisture-absorbingsurface so that the prepared sample forms a rectangle ofuniform thickness. Divide into
29、at least 20 segments of equalarea. With a flat bottom, square-nose tool, take scoopfuls ofapproximately equal size from each segment from the fulldepth of the bed. Combine the scoopfuls to form the testsample.NOTE 4Verify the adequacy of the grind on a separate sub-sample, do3Reagent Chemicals, Amer
30、ican Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Reagent Chemicals and Standards,byJoseph Rosin, D. Nostrand Co., Inc., New York, NY, and the United StatesPharmacopeia and Nation
31、al Formulary, U.S. Pharmacopeial Convention, Inc.(USPC), Rockville, MD.E1805 132not pass the laboratory sample through the 150-m sieve.11. Procedure11.1 Crucible Preparation:11.1.1 Add 106 g of fire assay flux mixture to each clay fireassay crucible.11.1.2 Weigh duplicate test samples: 14.583 g 6 0.
32、001 g.Record the test sample weights. Transfer the test samples to thefire-assay crucibles.11.1.3 Mix the contents of the crucible for 2 min in acrucible tumble mixer or perform equivalent flux mixingmanually.11.1.4 InquartationBased on the preliminary assay or anestimate, dispense the silver soluti
33、on over the top portion of themixed fire assay clay crucible to achieve an Ag to Au ratio of10 to 1. Alternatively, add silver foil in small chips to make thesame ratio.11.1.5 Place 55 g of PbO on top of the mixed fire assay claycrucible. Top with 3 g NaCl salt cover.11.2 Fusion:11.2.1 PrimaryPlace
34、the prepared crucibles carefully intoa room temperature fire assay furnace. Raise the temperature asrapidly as possible to 600 C and hold at that point until the saltcover melts. Elapsed time should be approximately 25 min.11.2.2 SecondaryIncrease temperature to 950 C and holduntil slag formation is
35、 completed. Time required is about 10min.11.2.3 TertiaryIncrease temperature to 1100 C and let thefusion material liquefy completely. Total time in the fire assayfurnace for all three fusion stages should be about 45 min.11.3 Pouring:11.3.1 When the fusion is completed, remove the cruciblewith the c
36、rucible tongs. Slowly swirl the crucible several times,tap the crucible lightly on an iron plate or table, then pour thecontents in the fusion assay mold.WARNINGRapidly cooling slag may eject sharp flyingfragments. Cover the mold with a wire screen immediatelyafter pouring.11.3.2 Save the crucible f
37、rom the fusion for the slag andcupel correction procedure (see 11.8.1).11.4 Lead Separation:11.4.1 After cooling, separate the lead button from the slagby tapping with a steel hammer. Save the slag for correctionprocedure (see 11.8). Carefully hammer the lead button into asquare shape, completely re
38、moving any adhering slag from thesurface.11.4.2 Save the slag from the fusion for the slag and cupelcorrection procedure (see 11.8.1).11.5 Cupellation:11.5.1 Place cupels into the furnace and preheat at 900 Cfor 30 min.11.5.2 Quickly place a lead button prepared as described in11.4.1 onto each cupel
39、. The lead button will melt into a brightlead puddle that will soon form a dark crust with the formationof surface PbO. The furnace temperature must be greater than888 C, the melting point of PbO. This step should beaccomplished within 1 min to 2 min.11.5.3 After 5 min, open the draft to the furnace
40、, anddecrease the temperature to 820 C. The ventilation should beregulated. If the temperature and draft conditions are correct, afringe of PbO crystals, known as “feathers” will appear aroundthe upper edge of the cupel.11.5.4 When the process of cupellation is near the end, oilyappearing drops of P
41、bO can be seen to collect on the surface ofthe remaining dor bead. These cause a rainbow color band tomove swiftly over the surface of the dor bead giving theillusion that the bead is revolving on a shifting axis. When thelast trace of PbO has been removed, this play of colorsdisappears and the dor
42、bead becomes duller than a normalmetallic luster. At this point remove the cupels from thefurnace and allow them to cool.WARNINGHot cupels emit lead fumes. Use properventilation.11.5.5 Remove the dor bead containing the precious metalfrom the cool cupel with bead pliers or tongs.11.5.5.1 Save the cu
43、pel from the cupellation for the slag andcupel correction procedure (see 11.8.1).11.5.6 Brush the dor bead with a bead brush to remove anyadhering cupel material.11.6 Parting:11.6.1 Flatten the dor bead with a hammer, then place it ina 50-mL porcelain crucible.411.6.2 Add 25 mL HNO3(1 + 7) to the cr
44、ucible with thedor bead. Place the crucible on a hot plate at 95 C and heatfor 30 min. Carefully decant the spent parting solution anddispose of properly.11.6.3 Repeat the parting and decanting step of 11.6.2 asecond time.11.6.4 Add 25 mL of HNO3(3 + 1) to the crucible. Heat for25 min. Carefully dec
45、ant the spent parting solution and discard.11.6.5 Wash the bead twice with NH4OH (1 + 9) to dissolveany silver chloride (AgCl2). Discard the liquid.WARNINGStronger NH4OH solutions left in the porce-lain crucible to “soak” the bead can form ammonium nitrateswhich may explode under certain conditions.
46、11.6.6 Dry beads in porcelain cups on a hot plate.11.6.7 Anneal the remaining gold at 650 C, then cool.Black or other colored deposits remaining inside the crucibleindicate inadequate washing. Off-colored gold indicates thepresence of impurities.11.7 WeighingWeigh the remaining gold bead to theneare
47、st 0.001 mg and record.11.8 Corrections:11.8.1 Combine the slag and cupels from the duplicatefusions for each test sample, weigh the total, and record.4Bugbee, E. E., “A Textbook of Fire Assaying,” John Wiley fire assay; gold content; gravim-etry5Supporting data have been filed at ASTM International
48、 Headquarters and maybe obtained by requesting Research Report RR:E01-1034.TABLE 2 Statistical InformationMaterial A B CLabo-ratoryAu,g/gAu,g/gAu,g/g1 0.14 0.59 17.62 0.22 0.57 17.63 0.15 0.61 18.04 0.21 0.55 17.95 0.14 0.66 18.16 0.10 0.57 18.07 0.17 0.58 17.9Mean 0.16 0.59 17.9srA0.02 0.05 0.15rB0
49、.05 0.16 0.41sRC0.04 0.06 0.23RD0.12 0.16 0.64%R 75 27 3.6ARepeatability standard deviation.BRepeatability limit, based on 95 % confidence limit.CReproducibility standard deviation.DReproducibility limit, based on 95 % confidence limit.TABLE 3 Bias InformationReferenceMaterialCertified Au,g/gAverage Au,g/gBias,g/gCanmet CCU1a 5.69 5.55 0.14Canmet CCU1b 5.89 5.45 0.40E1805 134ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of
