1、Designation: E1898 13Standard Test Method forDetermination of Silver in Copper Concentrates by FlameAtomic Absorption Spectrometry1This standard is issued under the fixed designation E1898; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, the year of 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 covers the determination of silver inthe range of 13 g/g to 500 g/g by acid dissol
3、ution of thesilver and measurement by atomic absorption spectrometry.Copper concentrates are internationally traded within thefollowing content ranges:Element Unit Content RangeAluminum % 0.05 to 2.50Antimony % 0.0001 to 4.50Arsenic % 0.01 to 0.50Barium % 0.003 to 0.10Bismuth % 0.001 to 0.16Cadmium
4、% 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 % 0.009 to 0.10Mercury g/g 0.
5、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 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This st
6、andard 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 regulatory limitations prior to its use.2. Referenced Document
7、s2.1 ASTM Standards:2D1193 Specification 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 Re
8、lating to Analytical Chemistry forMetals, Ores, and Related MaterialsE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical MethodE1763 Guide for Interpretation and Use of
9、Results fromInterlaboratory Testing of Chemical Analysis Methods3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E135.4. Summary of Test Method4.1 The analyst has the option of either digesting the samplein HNO3and HCl or HNO3and HClO4, depending on
10、 theirpreference and equipment availability. The filtered solutionsare aspirated into an air-acetylene flame of an atomic absorp-tion spectrometer. Spectral energy at approximately 328.1 nmfrom a silver hollow cathode lamp is passed through the flameand the absorbance is measured. This absorbance is
11、 comparedwith the absorbance of a series of standard calibration solu-tions.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 fl
12、otation for recovery of the metals.1This 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-lurgical Materials.Current edition appro
13、ved April 1, 2013. Published June 2013. Originallyapproved in 1997. Last previous edition approved in 2007 as E1898 - 07. DOI:10.1520/E1898-13.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards vo
14、lume 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 States15.2 This test method is a comparative method and isintended to be a referee method for compliance with c
15、ompo-sitional specifications for metal content or to monitor pro-cesses.5.3 It is assumed that all who use this method will be trainedanalysts capable of performing skillfully and safely. It isexpected that work will be performed in a properly equippedlaboratory and that proper waste disposal proced
16、ures will befollowed. Appropriate quality control practices must be fol-lowed such as those described in Guide E882.6. Interferences6.1 Elements normally found in copper concentrates do notinterfere. Use of instrumental background correction is re-quired to compensate for non specific absorption int
17、erferencesin the flame.7. Apparatus7.1 Atomic Absorption Spectrometer, capable of resolvingthe 328.1 nm silver line, equipped with an air-acetylene premixburner and a silver hollow cathode lamp. The performance ofthe instrument must be such that the response of silverabsorbance is linear over the ra
18、nge of 0.5 g/mL to 4.0 g/mL.8. Reagents and Materials8.1 Silver Calibration SolutionsBy means of pipets, trans-fer (0, 5, 10, 20, 30, and 40) mL of Silver Standard Solution B(8.3) into 100-mL volumetric flasks. Dilute to the mark withHC1 (1 + 3) and mix. These solutions are (0, 0.5, 1.0, 2.0, 3.0,an
19、d 4.0) g /mL, respectively.8.2 Silver Standard Solution A (1 mL = 1 mgAg)Dissolve1000 g of silver metal (purity: 99.99 %, minimum) in 50 mL ofHNO3(1+1). Dilute to about 100 mL and boil gently to expelthe oxides of nitrogen. Cool and transfer to a 1-L volumetricflask. Dilute to the mark and mix. Solu
20、tion must be clear,otherwise, discard it and repeat the preparation. Store in a darkbottle.NOTE 1All reagents must be free of chloride contamination.8.2.1 A certified reference solution meeting these specifica-tions may also be used.8.3 Silver Standard Solution B (1 mL= 10 gAg)Pipet 10mL of Silver S
21、tandard Solution A (8.2) into a 1-L volumetricflask containing 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 use.8.4 Purity of ReagentsReagent grade che
22、micals 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.3Other grades may be used,provided it is first ascertained that t
23、he reagent is of sufficienthigh purity to permit its use without lessening the accuracy ofthe determination.8.5 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type I or II of Specification D1193. Other reagent watertypes, Type III
24、 or Type IV, may be used if they do not causesilver precipitation or effect non-measurable change in theblank or sample.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 gros
25、s sample must be collected and prepared sothat it is representative of the lot of copper concentrate to beanalyzed.NOTE 2Gross samples may need to dried at low temperature in orderto determine the mercury content without drying losses.10.2 The laboratory sample must be ground, if necessary, sothat 1
26、00 % passes a 150 m sieve.NOTE 3Verify the adequacy of grind on a separate sub-sample. Do notpass the laboratory sample through the 150 m sieve.11. Preparation of Apparatus11.1 Follow the instrument manufacturers instructions toadjust the instrument for silver at 328.1 nm. Warm up theinstrument with
27、 background correction applied in accordancewith the manufacturers instructions.11.2 With the silver hollow cathode lamp in position,energized and stabilized, adjust the wavelength to maximizethe energy response of the 328.1 nm line.11.3 Light the burner, allow it to reach thermal equilibrium,and ad
28、just the instrument to zero while aspirating water.Aspirate the silver solution with the highest concentration fromthe series prepared in 8.1 and adjust the burner, acetylene, andair flow rates to obtain maximum response. Whenever one ormore of these parameters is changed, recalibration is necessary
29、.11.4 Aspirate the silver solution used in 11.3 to ensure thatthe absorbance reading is repeatable. Record six absorbancereadings, and calculate the standard deviation, s, of thereadings, as follows:s 5 0.40 A 2 B! (1)3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Soc
30、iety, 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 National Formulary, U.S. Pharmacopeial Convention, Inc.(USPC), R
31、ockville, MD.E1898 132where:A = highest of the six values found, andB = lowest of the six values found.NOTE 4Can also be calculated as follows:s 5c 2 d!2e 2 1!where:c = individual absorbance readings,d = mean of absorbance readings, ande = number of readings (6).11.5 Using water as a zero reference,
32、 and beginning with thesolution to which no addition of silver was made in 8.1,aspirate each calibration solution in ascending order ofconcentration, and record its absorbance. If the value of thesolution with the highest concentration used in 8.1 differs fromthe average of the six values in 11.4 by
33、 more than twice thestandard deviation, or by more than 0.01 multiplied by theaverage of the six values, whichever is greater, repeat themeasurement. If a problem is indicated, determine the cause,take appropriate corrective measures, and repeat 11.2-11.5.12. Calibration12.1 Calibration CurvePlot th
34、e average net absorbancevalues versus micrograms of silver per millilitre on rectangularcoordinate paper or calibrate in accordance with the manufac-turers instructions.12.2 Using water as a zero reference, aspirate calibrationstandards alternately until stable readings occur (within 2 %).Alternate
35、readings: three samples, a standard, three samplesand another standard, etc., until the absorbance for all samplesand standards have been determined at least three times. (Theabsorbances should repeat within 2 %). Average all values forstandards and samples. Plot curve of absorbance versus g/mLsilve
36、r in the standards. Read sample absorbance from the curveto obtain g/mL values of the samples. Standards and blankmust plot a straight line near zero absorbance on the graph.13. Procedure13.1 Test Solution:13.1.1 Select three test samples for each concentrate andtransfer an appropriate amount to tar
37、ed 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 0.1 1000Tra
38、nsfer to a 250-mL beaker.13.1.2 HNO3and HCl Decomposition:13.1.2.1 Place each test sample in a beaker as in 13.1.1.Add35 mL HNO3(1+1), cover with a watch glass, and heat gentlyuntil dissolution is complete.Add 10 mLHC1, slip cover aside,and evaporate to dryness. Dissolve the dry salts in 25 mL HC1(1
39、+3). Heat to boiling, then cool. Rinse watch glass and beakerwith HC1 (1+3) and filter through a dry high-wet strength,medium-porosity filter paper4into a clean volumetric flaskWash the paper eight times with HC1 (1+3) and discard thepaper. Dilute to volume with HC1 (1+3) and mix.NOTE 5Some copper c
40、oncentrates may not be totally decomposed bythese digestion methods. The user is advised to check any residue from thedigestion procedure for residual silver.13.1.3 HNO3and HClO4Decomposition:13.1.3.1 Place each test sample in a beaker as in 13.1.1.Add35 mL HNO3(1+1), cover with a watch glass, and h
41、eat gentlyuntil dissolution is complete and oxides of nitrogen aredispelled. Cautiously add 10 mL of HClO4and continueheating (see Note 6). Evaporate to dense white fumes. Con-tinue fuming to near dryness.NOTE 6Handle HClO4in accordance with practices E50 as follows:HClO4can be used safely, but only
42、 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-established procedures should be employed for H
43、ClO4oxidations 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 collect in the ducts or blower.13.1.3.2 Cool s
44、lightly and dissolve salts in 35 mL HC1(1+3). Heat to boiling. Allow to cool again. Rinse watch glassand beaker with HC1 (1+3) and filter through a dry, highwet-strength, medium- porosity filter paper4into a volumetricflask. Wash the paper eight times with HC1 (1+3) and discardthe paper. Dilute to v
45、olume with HCl (1+3) and mix.13.2 Prepare a reagent blank by treating the same amount ofall reagents as directed in 13.1.2 or 13.1.3. Use reagents fromthe same lots for blank and test solutions.13.3 MeasurementUsing water as a zero reference, aspi-rate calibration standards alternately until stable
46、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 least4Whatman No. 54 or No. 541 has been found suitable.FIG. 1 Ag in Cu concentrates: HNO3-HCl MethodE1898 133
47、three times. (The absorbances should repeat 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 zeroabsorban
48、ce on the graph.14. Calculation14.1 Convert 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 content of silver as follows:E 5 CA 2 B!/D (2)where:A = g of silv
49、er per mL in the final test solution,B = 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 content in the test sample, g/g14.2 Average the test results for the triplicate test sampleportions and round the results in accordance with Practice E29,to the nearest g/g, using the rounding method.15. Precision and Bias515.1 PrecisionThirty-one laboratories cooperated in test-ing these methods and obtained the statistical informationsummarized in Table 1
