1、Designation: E 945 07Standard Test Method forDetermination of Zinc in Zinc Ores and Concentrates byComplexometric Titrimetry1This standard is issued under the fixed designation E 945; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision,
2、 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 zinc inores, concentrates, and related materials having che
3、micalcomposition within the following limits:Element Concentration Range, %Zinc 5.0 to 70.0Lead 0.5 to 50.0Copper 0.1 to 3.0Iron 0.5 to 16.0Sulfur 4.0 to 30.0Calcium 0.1 to 20.0Magnesium 0.1 to 10.0Cadmium 0.1 to 8.0Arsenic 0.01 to 1.0Antimony 0.01 to 0.005Bismuth 0.001 to 0.1Cobalt 0.1 to 0.5Nickel
4、 0.3 to 3.0Silver 0.00 to 150 oz/tonGold 0.00 to 1.0 oz/ton1.2 This standard 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-bi
5、lity of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 1193 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 Chemica
6、l Analysis of Metals, Ores, andRelated MaterialsE 135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE 173 Practice for Conducting Interlaboratory Studies ofMethods for Chemical Analysis of Metals3E 663 Practice for Flame Atomic Absorption Analysis3E 882 Guide for
7、 Accountability and Quality Control in theChemical Analysis LaboratoryE 1024 Guide for Chemical Analysis of Metals and MetalBearing Ores by Flame Atomic Absorption Spectropho-tometry4E 1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method3. Terminol
8、ogy3.1 DefinitionsFor definitions of terms used in this testmethod, refer to Terminology E 135.4. Summary of Test Method4.1 The sample, after appropriate acid decomposition, isevaporated to near dryness. The salts are dissolved in acid,interfering elements are removed, and the zinc is extracted asth
9、iocyanate complex into MIBK. Zinc is determined in theextract by titrating with EDTA, using an internal indicator.5. Significance and Use5.1 This test method is primarily intended to test materialsfor compliance with compositional specifications. It is assumedthat all who use this test method will b
10、e trained analystsworking in properly equipped laboratories.5.2 Appropriate quality control practices shall be followedsuch as those described in Guide E 882.6. Interferences6.1 With the exception of cadmium and cobalt, elements donot interfere if their concentrations are under the maximumlimits sho
11、wn in 1.1.6.2 When the cadmium content is above 5.0 % in thematerial to be analyzed, some of the cadmium is extracted andwill titrate as zinc. The addition of potassium iodide before thetitration serves to prevent the interference of cadmium. Theamount of potassium iodide solution to add in order to
12、 preventthe interference of cadmium is listed in 13.10.3.1This 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.
13、Current edition approved July 15, 2007. Published July 2007. Originallyapproved in 1983. Last previous edition approved in 2002 as E 945 02a.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volu
14、me information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Withdrawn.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6.3 Cobalt is extracted and titrated with the zinc. If thecobalt content of the mat
15、erial to be analyzed is less than0.05 %, the interference is negligible. For cobalt contentsgreater than 0.05 %, the cobalt must be extracted as outlined in13.9.5.7. Apparatus7.1 Atomic absorption spectrophotometers shall conform toPractice E 663 or Guide E 1024.7.2 Magnetic Stirrer, with TFE-fluoro
16、carbon covered mag-netic stirring bar. A magnetic stirrer provided with illuminationis preferred.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committe
17、e onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.5Other 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 determination.8.2 Purity of WaterUnless other
18、wise indicated, referencesto water shall be understood to mean reagent water as definedby Type I of Specification D 1193.8.3 Ammonium Fluoride Solution (250 g/L)Dissolve 250g of ammonium fluoride (NH4F) in water and dilute to 1 L.Store in a polyethylene bottle.8.4 Ammonium Chloride Solution (250 g/L
19、)Dissolve 250g of ammonium chloride (NH4Cl) in water and dilute to 1 L.8.5 Ammonium Thiocyanate (500 g/L)Dissolve 500 g ofammonium thiocyanate (NH4SCN) in distilled water and diluteto1L.8.6 Buffer Solution (pH 5.5)Dissolve 250 g of hexameth-ylenetetramine (C6H12N4) in 750 mL of water. Add 57 mL ofac
20、etic acid, dilute to 1 L, and mix.8.7 Chloroform (CHCl3).8.8 Disodium Ethylenedinitrilo Tetraacetate Dihydrate(EDTA) Standard SolutionPrepare a solution as follows:8.8.1 PreparationDissolve disodium ethylenedinitrilo tet-raacetate (EDTA) dihydrate in water, transfer to a 1L volu-metric flask, dilute
21、 to volume, and mix. The solution is stablefor several months when stored in plastic or borosilicate glassbottles.Use the following table as a guide for the specific weight ofEDTA 2H2O to use.NOTE 1The use of varying concentrations of EDTA solution allowsthe volume of the titrant to be between 30 an
22、d 50 mL.Amount ofEDTA 2H2O EDTA Standard ZincIf the expectedzinc is:Weight, g/L Concentration Solution toUse5 to 20 % 6.642 6 g/L 10 mL20 to 40 % 13.29 12 g/L 30 mL40 to 56 % 17.71 16 g/L 40 mL56 to 70 % 22.14 20 g/L 50 mL8.8.2 Standardize the EDTA solution by pipetting the sug-gested amount of stan
23、dard zinc solution into a 250-mLseparatory funnel.Add 10 drops of ferric chloride solution, adddistilled water to adjust volume to 50 mL, mix, and proceed asdirected in 13.9.2. It is recommended that replicate standard-izations be made to ensure better accuracy.8.8.3 Calculate the zinc equivalent of
24、 the EDTA solution asfollows:Zinc equivalent, mg/mL!5AB(1)where:A = zinc in the chosen aliquot, mg andB = EDTA solution used, mL8.9 Ethanol (CH3CH2OH)Certain denatured ethanols in-terfere with the color of the indicator during the titration. Pureethanol is recommended for this reason.8.10 Ferric Chl
25、oride Solution (140 g/L)Dissolve 14 g offerric chloride (FeCl36H2O) in water and dilute to 100 mL.8.11 4-Methyl-2-Pentanone (MIBK)CH3COCH2CH(CH3)2.8.12 2-Nitroso-1-Naphthol Solution (10 g/L)Dissolve 0.5g of 2-nitroso-1-naphthol (NOC10H6OH) in 50 mL of aceticacid. Prepare fresh as needed.8.13 Potassi
26、um Iodide (1000 g/L)Dissolve 100 g ofpotassium iodide (KI) in distilled water and dilute to 100 mL.8.14 Sodium Fluoride Solution (20 g/L)Dissolve 10 g ofsodium fluoride (NaF) in water and dilute to 500 mL. Store ina polyethylene bottle.8.15 Thiourea Solution (100 g/L)Dissolve 50 g of thio-urea (NH2C
27、SNH2) in water and dilute to 500 mL.8.16 Xylenol Orange Tetrasodium Salt Indicator Solution (2g/L)Dissolve 100 mg of xylenol orange tetrasodium salt inwater and dilute to 50 mL.8.17 Zinc, Standard Solution (1 mL3.50 mg)Dissolve3.50 g of zinc (minimum purity 99.99 %) in 10 mL of HNO3and 25 mL of wate
28、r. Heat gently; when dissolution is complete,boil. Cool. Transfer to a 1-L flask. Dilute to the mark and mixthoroughly.9. Hazards9.1 For precautions to be observed in the use of certainreagents in this test method, refer to Practices E50.10. Sampling and Sample Preparation10.1 The gross sample shall
29、 be collected and prepared so asto be representative of the material to be analyzed.10.2 Pulverize the laboratory sample to pass a No. 100(150-m) sieve. The repeatability, R1, of Practice E 173corresponds to the repeatability index, r, of Practice E 1601.5Reagent Chemicals, American Chemical Society
30、 Specifications , AmericanChemical Society, Washington, DC (www.acs.org). For suggestions on the testing ofreagents not listed by the American Chemical Society, see Reagent Chemicals andStandards, by Joseph Rosin, D. Nostrand Co., Inc., New York, NY, and the UnitedStates Pharmacopeia and National Fo
31、rmulary, U.S. Pharmaceutical Convention,Inc. (USPC), Rockville, MD (www.usp.org).E94507211. Rounding Calculated Values11.1 Calculated values shall be rounded to the desirednumber of places as directed in the Rounding-Off Proceduresection of Practice E29.12. Interlaboratory Studies12.1 This test meth
32、od has been evaluated in accordancewith Practice E 173. For those methods tested according toPractice E 173, the reproducibility, R2, of Practice E 173corresponds to the reproducibility index, R, of Practice E 1601.13. Procedure13.1 Weigh approximately 2.5 g of sample into a weighingbottle. Dry the
33、bottle and contents at least1hat105C,butnotmore than 3 h. Cap the bottle and cool to room temperature ina desiccator.13.1.1 Momentarily release the cap to equalize the pressureand weigh the capped bottle and sample to the nearest 0.1 mg.13.1.2 Transfer all of the sample into a 250 to 300-mLErlenmeye
34、r flask or Phillips beaker. Reweigh the capped bottleto the nearest 0.1 mg. The difference between the weightrecorded in 13.1.1 and the weight recorded in 13.1.2 is theweight of the sample.13.2 Moisten the sample in the Erlenmeyer flask withapproximately 5 mL of water and add 2 to 3 mL bromine.Allow
35、 to stand for 15 min with occasional stirring.13.3 Add 10 mL of HNO3cautiously and allow to stand for5 min with occasional stirring.13.4 Cautiously add 15 mL of H2SO4(1 + 1), mix, and heatgently to remove the brown bromine and nitric oxide fumes.Do not boil.13.5 Remove from the heat, add 3 to 5 drop
36、s of HF, 5 mLof HClO4, replace on the hotplate, and evaporate the solutionuntil the volume is reduced to approximately 5 mL.13.6 Remove from the heat, wash down the sides withwater, add 5 mL of H2SO4(1 + 1), 1 mL of HCl (1 + 4), anddilute to 40 mL. Mix and bring to a boil.13.6.1 For samples containi
37、ng more than 10 % SiO2, pro-ceed as directed in 13.7. For samples containing less than 10 %SiO2, proceed as directed in 13.8.13.7 Filter the solution into a 500-mL volumetric flask,using a Whatman #1 or equivalent paper. Wash the residuethoroughly to remove soluble precipitate.13.7.1 Transfer the pa
38、per plus residue into a platinumcrucible. Char the paper at a low temperature and then ignite ina muffle furnace at 800 C. Remove from the furnace and cool.13.7.2 Add 5 mL of HF, 5 mL of HClO4, mix, and heat untildense fumes are being given off. Remove from the heat andcool.13.7.3 Dilute with water
39、and transfer to the 500-mL volu-metric flask, which contains the filtrate from 13.7. Dilute tovolume and mix. Allow any remaining residue to settle.13.8 Transfer the solution obtained in 13.6 to a 500-mLvolumetric flask. Dilute to volume and mix. Allow anyremaining residue to settle.13.9 Extraction:
40、13.9.1 Pipet 50 mL of the clear solution obtained in 13.7.3or 13.8 into a 250 mL separatory funnel.Add 10 drops of ferricchloride solution and mix.NOTE 2Ferric chloride is added to aid the analyst in setting the pH ofthe solution. If iron is present in the sample already, the addition of theferric c
41、hloride solution can be eliminated.13.9.2 Add 20 mL of NH4Cl solution and mix.13.9.3 Add NH4OH, dropwise, until a slight turbidity de-velops. Then add 5 mL of HCl (1 + 4) and mix.13.9.4 Add 20 mL of NH4F solution and mix.13.9.4.1 If the cobalt content of the sample is known to beless than 0.05 %, pr
42、oceed as directed in 13.9.6. When thecobalt content is higher than 0.05 %, the cobalt must beremoved. Proceed as directed in 13.9.5.13.9.5 Adjust the pH using pH paper to between 3 and 4 bythe dropwise additions of HCl (1 + 1) or NH4OH (1 + 1)solution. Add 5 drops of H2O2(30 %) and 2 mL of 2-nitroso
43、-1-napthol solution. Allow to stand 30 min with occasionalstirring.13.9.5.1 Add 20 mL of CHCl3, shake for 30 s, and allow thephases to separate. Discard the lower phase.13.9.5.2 Add another 20 mL of CHCl3and repeat theextraction again discarding the lower phase.13.9.5.3 Extract a third time using 10
44、 mL of CHCl3anddiscard the lower phase. Proceed as directed in 13.9.6.13.9.6 Add 5 mL of thiourea solution and 25 mL NH4SCNsolution, mixing after each addition.13.9.7 Add 80 mLof MIBK and shake vigorously for 1 min.Allow the phases to separate, and then draw off the loweraqueous phase into a second
45、separatory funnel. Retain theupper organic phase.13.9.8 Add 20 mL of MIBK to the second separatory funneland shake for 1 min. Allow the phases to separate and discardthe lower aqueous phase. Retain the upper organic phase.13.9.9 Transfer the portions from both separatory funnels toa 400-mL beaker. T
46、o each separatory funnel add 1 mL of HCl(1 + 4) and 50 mL of ethanol and shake for 5 s. Transfer bothof these solutions to the 400-mL beaker. Cover the beaker untilthe titration is to begin.13.10 Titration:13.10.1 Place a stirring bar into the solution in the 400-mLbeaker and place the beaker on a m
47、agnetic stirrer. Begin to stirat a moderate rate.13.10.2 While stirring, add 10 mL of NaF solution, 10 mLof thiourea solution, and 20 mL of buffer solution.13.10.3 If the cadmium content of the original sample isbelieved to be from 5 to 10 % add 10 mL of KI solution.13.10.4 Add 10 drops of xylenol o
48、range indicator solutionand 0.25 to 0.30 g ascorbic acid, and continue to stir. Titratewith the appropriate EDTAsolution chosen as prescribed in 8.8to a yellow end point.NOTE 3The reaction between EDTA and zinc is slowed down in thepresence of organic solvents. On approaching the equivalence point,
49、it isnecessary to work more slowly than usual. Wait 10 s after each additionof EDTA. Should a phase separation occur or the sample become cloudy,add 20 mL of ethanol and proceed with the titration.NOTE 4If the end-point is inadvertently passed, add 1.00 mL of zincstandard solution by means of a microburet. Complete the titration asusual. Correct the final result for the quantity of zinc added.E94507314. Calculation14.1 Calculate the percentage of zinc as follows:Zinc, % 5C 3 D! 2 FE 3 10(2)where:C = EDTA used, mL,D = zinc equivalent, (mg/mL) EDTA sol
