1、Designation: E 1898 07Standard Test Method forDetermination of Silver in Copper Concentrates by FlameAtomic Absorption Spectrometry1This standard is issued under the fixed designation E 1898; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, 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 test method covers the determination of silver inthe range of 50 g/g to 1000 g/g by acid di
3、ssolution of thesilver and measurement by atomic absorption spectrophotom-etry. Copper concentrates are internationally traded within thefollowing concentration ranges:Element Unit Concentration RangeAluminum % 0.05 to 2.50Antimony % 0.0001 to 4.50Arsenic % 0.01 to 0.50Barium % 0.003 to 0.10Bismuth
4、% 0.001 to 0.16Cadmium % 0.0005 to 0.04Calcium % 0.05 to 4.00Carbon % 0.10 to 0.90Chlorine % 0.001 to 0.006Chromium % 0.0001 to 0.10Cobalt % 0.0005 to 0.20Copper % 10.0 to 44.0Fluorine % 0.001 to 0.10Gold g/g 1.40 to 100.0Iron % 12.0 to 30.0Lead % 0.01 to 1.40Magnesium % 0.02 to 2.00Manganese % 0.00
5、9 to 0.10Mercury g/g 0.05 to 50.0Molybdenum % 0.002 to 0.25Nickel % 0.0001 to 0.08Silicon % 0.40 to 20.0Silver g/g 18.0 to 8000Sulfur % 10.0 to 36.0Tin % 0.004 to 0.012Zinc % 0.005 to 4.301.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is
6、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 its use.2. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterE29 Practice for Using Significant Digits
7、in Test Data toDetermine Conformance with SpecificationsE50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 633 Guide for Use of Thermoc
8、ouples in Creep andStress-Rupture Testing to 1800F (1000C) in AirE 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 1601 Practice for Conducting an Int
9、erlaboratory Study toEvaluate the Performance of an Analytical MethodE 1763 Guide for Interpretation and Use of Results fromInterlaboratory Testing of Chemical Analysis Methods3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E 135.4. Summary of Test
10、 Method4.1 The analyst has the option of either digesting the samplein nitric and hydrochloric acids or nitric and perchloric acids,depending on their preference and equipment availability. Thefiltered solutions are aspirated into an air-acetylene flame of anatomic absorption spectrophotometer. Spec
11、tral energy at ap-proximately 328.1 nm from a silver hollow cathode lamp ispassed through the flame and the absorbance is measured. Thisabsorbance is compared with the absorbance of a series ofstandard calibration solutions.1This test method is under the jurisdiction of ASTM Committee E01 onAnalytic
12、al Chemistry for Metals, Ores and Related Materials and is the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edition approved June 1, 2007. Published June 2007. Originallyapproved in 1997. Last previous edition approved in 2002 as E 1
13、898 - 02.2For referenced ASTM standards, visit the ASTM website, 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.3Withdrawn.1Copyright ASTM International, 100 Barr H
14、arbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 In the primary metallurgical processes used by themineral processing industry for copper bearing ores, copperand silver associated with sulfide mineralization are concen-trated by the process of flot
15、ation for recovery of the metals.5.2 This test method is intended to be a referee method forthe determination of silver in copper concentrates. It is as-sumed that all who use this procedure will be trained analystscapable of performing common laboratory procedures skill-fully and safely. It is expe
16、cted that work will be performed ina properly equipped laboratory and that proper waste disposalprocedures will be followed. Appropriate quality control prac-tices must be followed such as those described in Guide E 882.6. Interferences6.1 Elements normally found in copper concentrates do notinterfe
17、re. Use of instrumental background correction is re-quired to compensate for non specific absorption interferencesin the flame.7. Apparatus7.1 Atomic Absorption Spectrophotometer, capable of re-solving the 328.1 nm silver line, equipped with an air-acetylenepremix burner and a silver hollow cathode
18、lamp. The perfor-mance of the instrument must be such that the response ofsilver absorbance is linear over the range of 0.5 to 4.0 g/mL.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents confor
19、m to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficienthigh purity to permit its use without lessening the accuracy ofthe determ
20、ination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type I of Specification D 1193.8.3 Silver Standard Solution A (1 mL = 1 mg Ag)Dissolve 1000 g of silver metal (purity: 99.99 %, minimum) in50 mL of HNO3(1+1). Dilute to ab
21、out 100 mL and boil gentlyto expel the oxides of nitrogen. Cool and transfer to a 1-Lvolumetric flask. Dilute to the mark and mix. Solution must beclear, otherwise, discard it and repeat the preparation. Store ina dark bottle.NOTE 1All reagents must be free of chloride contamination.8.4 Silver Stand
22、ard Solution B (1 mL = 10 g Ag)Pipet10 mLof Silver Standard SolutionAinto a 1-Lvolumetric flaskcontaining about 500 mL of water and 250 mL of HCl. Mix,cool, dilute to the mark, and remix. If turbid, discard thesolution and repeat the preparation. Transfer to a dark bottle.Prepare immediately before
23、use.9. Hazards9.1 For precautions to be observed in the use of certainreagents and equipment in this test method, refer to PracticesE50.10. Sampling and Sample Preparation10.1 The gross sample must be collected and prepared sothat it is representative of the lot of copper concentrate to beanalyzed.
24、The laboratory sample must be pulverized, if neces-sary, so that 100 % passes a No. 100 (150 m) sieve.NOTE 2Verify the adequacy of grind on a separate sub-sample. Do notpass the laboratory sample through the No. 100 sieve.11. Calibration and Standardization11.1 Calibration SolutionsBy means of pipet
25、s, transfer 0,5, 10, 20, 30, and 40 mL of Silver Standard Solution B into100-mL volumetric flasks. Dilute to the mark with HC1 (1+3)and mix. These solutions are 0, 0.5, 1.0, 2.0, 3.0, and 4.0 gAg/mL, respectively.11.2 Photometry:11.2.1 With the silver hollow cathode lamp in position,energized and st
26、abilized, adjust the wavelength to maximizethe energy response of the 328.1 nm line.11.2.2 Light the burner, allow it to reach thermal equilib-rium, and adjust the instrument to zero while aspirating water.Aspirate the silver solution with the highest concentration fromthe series prepared in 11.1 an
27、d adjust the burner, acetylene, andair flow rates to obtain maximum response. Whenever one ormore of these parameters is changed, recalibration is necessary.11.2.3 Aspirate the silver solution used in 11.2.2 to ensurethat the absorbance reading is repeatable. Record six absor-bance readings, and cal
28、culate the standard deviation, s,ofthereadings, as follows:s 5 0.40 A2B! (1)where:A = highest of the six values found, andB = lowest of the six values found.11.2.4 Using water as a zero reference, and beginning withthe solution to which no addition of silver was made in 11.1,aspirate each calibratio
29、n solution in ascending order of con-centration, and record its absorbance. If the value of thesolution with the highest concentration used in 11.1 differsfrom the average of the six values in 11.2.3 by more than twicethe standard deviation, or by more than 0.01 multiplied by theaverage of the six v
30、alues, whichever is greater, repeat themeasurement. If a problem is indicated, determine the cause,take appropriate corrective measures, and repeat 11.2.1-11.2.4.11.2.5 Calibration CurvePlot the average net absorbancevalues versus micrograms of silver per millilitre on rectangularcoordinate paper. T
31、est for linearity as described in GuideE 1024.12. Procedure12.1 Test Solution:4“Reagent Chemicals, American Chemical Society Specifications,” AmericanChemical Society, Washington DC. (www.acs.org). For suggestions on the testing ofreagents not listed by the American Chemical Society, see “Reagent Ch
32、emicals andStandards,” by Joseph Rosin, D. Nostrand Co., Inc., New York, NY, and the “UnitedStates Pharmacopeia and National Formulary,” U.S. Pharmocopeia Convention, Inc.(USPC), Rockville, MD (www.usp.org).E189807212.1.1 Select three test samples for each concentrate andtransfer an appropriate amou
33、nt to tared weighing vessels. Dryat 105 C in a drying oven for at least two hours to constantweight. Select final weights in accordance with the following:Est. Ag, g/g Sample Wt., g Wt. Tolerance, mg Dil., mL20-150 2.0 0.1 100150-300 2.0 0.1 200300-500 1.0 0.1 200500-1000 1.0 0.1 5001000-3000 1.0 0.
34、1 1000Transfer to a 250-mL beaker.12.1.2 Nitric and Hydrochloric Acid Decomposition:12.1.2.1 Place each test sample in a beaker as in 12.1.1.Add35 mL HNO3(1+1), cover with a watchglass, and heat gentlyuntil dissolution is complete.Add 10 mLHC1, slip cover aside,and evaporate to dryness. Dissolve the
35、 dry salts in 25 mL HC1(1+3). Heat to boiling, then cool. Rinse watchglass and beakerwith HC1 (1+3) and filter through a dry high-wet strength,medium-porosity filter paper5into a clean volumetric flask, asshown in 12.1.1. Wash the paper eight times with HC1 (1+3)and discard the paper. Dilute to volu
36、me with HC1 (1+3) andmix.NOTE 3Some copper concentrates may not be totally decomposed bythese digestion methods. The user is advised to check any residue from thedigestion procedure for residual silver.12.1.3 HNO3and HClO4Decomposition:12.1.3.1 Place each test sample in a beaker as in 12.1.1.Add35 m
37、L HNO3(1+1), cover with a watchglass, and heat gentlyuntil dissolution is complete and oxides of nitrogen aredispelled. Cautiously add 10 mL of HClO4and continueheating (see Note 4). Evaporate to dense white fumes. Con-tinue fuming to near dryness.NOTE 4Handle HClO4in accordance with practices E50as
38、 follows:HClO4can be used safely, but only under carefully prescribed conditions.Dilute HClO4has the same hazardous properties as other strong acids, butthe concentrated acid, especially when it is hot, reacts rapidly and oftenwith violently explosive force with oxidizable materials. Only well-estab
39、lished procedures should be employed for HClO4oxidations and theprocedures should be followed exactly as written. Specially designedhoods are specified for handling HClO4fumes and any hood in whichHClO4may be fumed should not be used for other operations that permiteasily oxidizable material to coll
40、ect in the ducts or blower.12.1.3.2 Cool slightly and dissolve salts in 35 mL HC1(1+3). Heat to boiling. Allow to cool again. Rinse watchglassand beaker with HC1 (1+3) and filter through a dry, highwet-strength, medium- porosity filter paper5into a volumetricflask as described in 12.1.2.1. Wash the
41、paper eight times withHC1 (1+3) and discard the paper. Dilute to volume with HCl(1+3) and mix.12.2 Prepare a reagent blank by treating the same amount ofall reagents as directed in 12.1.2 or 12.1.3. Use reagents fromthe same lots for blank and test solutions.12.3 PhotometryUsing water as a zero refe
42、rence, aspiratecalibration standards alternately until stable readings occur(within 2 %). Alternate readings: three samples, a standard,three samples and another standard, etc., until the absorbancefor all samples and standards have been determined at leastthree times. (The absorbances should repeat
43、 within 2 %).Average all values for standards and samples. Plot curve ofabsorbance versus g/mL silver in the standards. Read sampleabsorbance from the curve to obtain g/mL values of thesamples. Standards and blank must plot a straight line near zeroabsorbance on the graph.13. Calculation13.1 Convert
44、 the absorbance of the test sample solutionsand the reagent blank solution to micrograms of silver permillilitre of the final dilution volume by means of the calibra-tion curve. Calculate the concentration of silver as follows:E 5 CA2B!/D (2)where:A = g of silver per mL in the final test solution,B
45、= g of silver per mL in the final reagent blank,C = final volume of test solution, mL,D = weight of dry sample in final volume, g, andE = silver concentration in the test sample, g/g13.2 Average the test results for the triplicate test sampleportions and round the results in accordance with Practice
46、E29, to the nearest g/g, using the rounding method.14. Precision and Bias614.1 PrecisionThirty-one laboratories cooperated in test-ing these methods and obtained the statistical informationsummarized in Table 1 and Table 2. The reproducibility indexdata fits the analytical error model of Guide E 176
47、3 as afunction of silver content:HNO3HCl: R 5 =6.4921 0.1239 CAg!2(3)HNO3HClO4: R 5 =5.3021 0.1402 CAg!2(4)where:5Whatman No. 54 or No. 541 has been found suitable.6Supporting data have been filed at ASTM International Headquarters. RequestRR:E011020.FIG. 1 Ag in Cu concentrates: HNO3-HCl MethodE189
48、8073CAg= concentration of silver, g/gThese relationships are plotted in Fig. 1 and Fig. 2. Theequations or Table 3 may be used to approximate the repro-ducibility index to be expected at various silver contents.14.2 BiasThe bias of the test method is indicated by themean of interlaboratory results f
49、or sample 91-8 which is anaccepted reference material, CANMET CCU-1a. The acceptedreference value is 144.8 g/g Ag and the mean of theinterlaboratory study is 141 g/g Ag, indicating a slightly lowbias in the method. The bias, however is less than thereproducibility (R) for the method. It is recommended that theuser of the test method include accepted reference materialsand compare the accepted values for the reference materialswith the mean of the test results. When the mean of the testresults is outside of the accepted range for the referencem
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