1、Designation:E34204 Designation:E34211Standard Test Method for Determination of Chromium Oxidein Chrome Ores by Permanganate Titrimetry1This standard is issued under the fixed designation E342; the number immediately following the designation indicates the year oforiginal adoption or, in the case of
2、revision, 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.Scope1.1This test method covers the determination of chromium oxide (Cr2O3) in chrome ores in the concentr
3、ation range from 25 to60%.1.2) in chrome ores in the compositional range from 25 % to 60 %.NOTE1As used in this test method, “%” refers to a mass fraction (wt/wt %) (g/100g).1.2The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1
4、.3This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2.Referenced Docume
5、nts2.1ASTM Standards:2D1193Specification for Reagent WaterE50Practices for Apparatus, Reagents, and Safety Considerations for Chemical Analysis of Metals, Ores, and Related MaterialsE135Terminology Relating to Analytical Chemistry for Metals, Ores, and Related MaterialsE276Test Method for Particle S
6、ize or Screen Analysis at No. 4 (4.75-mm) Sieve and Finer for Metal-Bearing Ores and RelatedMaterialsE882Guide for Accountability and Quality Control in the Chemical Analysis Laboratory3.Terminology3.1 DefinitionsFor definitions of terms used in this test method, refer to Terminology E135.4.Summary
7、of Test Method4.1The sample is decomposed by fusion with sodium peroxide. After leaching in water and boiling to decompose peroxides, thesolution is acidified with nitric and sulfuric acids. Residual chromium is oxidized to chromate with silver nitrate, potassiumpermanganate, and peroxydisulfate. Th
8、e excess of permanganate is destroyed by the addition of sodium chloride. After cooling,the chromate is reduced by the addition of a measured excess of a ferrous ammonium sulfate, and the excess is titrated with astandard permanganate solution.5.Significance and Use5.1This test method is intended to
9、 be used for compliance with compositional specifications for chromium oxide content inchromium-bearing ores. It is assumed that all who use these procedures will be trained analysts capable of performing commonlaboratory procedures skillfully and safely. It is expected that work will be performed i
10、n a properly equipped laboratory and thatproper waste disposal procedures will be followed. Appropriate quality control practices must be followed such as those describedin Guide E882.6.Interferences6.1None of the elements normally found in chrome ores interfere with this test method.1This test meth
11、od is under the jurisdiction of ASTM Committee E01 on Analytical Chemistry for Metals, Ores, and Related Materials and is the direct responsibility ofSubcommittee E01.02 on Ores, Concentrates, and Related Metallurgical Materials.Current edition approved MayDec. 1, 2004.2011. Published June 2004.Janu
12、ary 2012. Originally approved in 1967. Last previous edition approved in 19992004 asE34299.E34204. DOI: 10.1520/E0342-04.10.1520/E0342-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume
13、 information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequa
14、tely depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
15、n, PA 19428-2959, United States.7.Reagents and Materials7.1Purity of ReagentsReagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where su
16、chspecifications are available3. Other grades may be used, provided it is first ascertained that the reagent is of sufficiently high purityto permit its use without lessening the accuracy of the determination.7.2Purity of WaterUnless otherwise indicated, references to water shall be understood to me
17、an reagent water as defined byconforming to Type I or II of Specification D1193. . Type III or IV may be used if they effect no measurable change in the blankor sample.7.3Ammonium Peroxydisulfate Solution (250 g/L)Dissolve 25 g of ammonium persulfate (ammonium peroxydisulfate)(NH4)2S2O8) in water, a
18、nd dilute to 100 mL. Prepare fresh as needed.7.4Ferrous Ammonium Sulfate, Standard Solution7.4Ferrous Ammonium Sulfate Solution(0.2 N)Dissolve 78.4 g of ferrous ammonium sulfate (FeSO4(NH4)2SO46H2O) in 1L of cool H2SO4(5+95). As (5 + 95). Because the ferrous ammonium sulfate solution gradually weake
19、ns in reducing power, itis necessary to standardize it daily, the ferrous ammonium sulfate solution daily or at the same time that the chrome ore is analyzed.To standardize, transfer 100 mL of FeSO4(NH4)2SO46H2O to a 600-mL beaker, dilute to 300 mL with cold H2SO4(5 + 95), add2mLofH3PO4and 2 drops o
20、f ortho-phenanthroline ferrous sulfate (Fferroin). Titrate immediately with 0.2 N KMnO4solution(7.9) to a faint, permanent pink color.7.5Ferrous Sulfate Solution (0.025 M)Dissolve 6.95 g of ferrous sulfate (FeSO47H2O) in 500 mL of water and dilute to 1L.7.6Nitric Acid (sp gr 1.42)Concentrated nitric
21、 acid (HNO3).7.7Ortho-Phenanthroline Ferrous Sulfate Indicator Solution (0.025 M)Dissolve 1.485 g of 1,10-phenanthroline monohy-drate in 100 mL of ferrous sulfate solution (FeSO47H2O).7.8O) prepared in 7.5.7.7Phosphoric Acid (sp gr 1.69)(specific gravity 1.69 g/mL)Concentrated phosphoric acid (H3PO4
22、).7.97.8Potassium Permanganate Solution (20 g/L)Dissolve 20 g of potassium permanganate (KMnO4) in water and dilute to 1L.7.10Potassium Permanganate, Standard Solution7.9Potassium Permanganate Solution(0.2 N)Dissolve 6.4 g of KMnO4in 1 L of water. Standardize against the NationalInstitute of Standar
23、ds and Technology Standard sodium oxalate or equivalent.7.11in 1 L of water. Standardize against a National Institute of Standards and Technology Reference Material for sodium oxalate(Na2C2O4) or equivalent.7.10Silver Nitrate Solution (8 g/L)Dissolve8gofsilver nitrate (AgNO3) in water and dilute to
24、1 L.7.127.11Sodium Chloride Solution (100 g/L)Dissolve 10 g of sodium chloride (NaCl) in water and dilute to 100 mL.7.137.12Sodium Peroxide (Na2O2).7.14Sulfuric Acid (1+1)Carefully pour 1 volume of concentrated sulfuric acid (H2SO4, sp gr 1.84) into 1 volume of water.7.15Sulfuric Acid (5+95)Carefull
25、y pour 5 volumes of concentrated H2SO4(sp gr 1.84) into 95 volumes of water.8.Hazards8.1For precautions to be observed in this method, refer to Practices E50.9.Sampling, Test Specimens, and Test Units9.1The test unitmaterial shall be pulverized so that at least 95 % passes a No. 100 (150-m) sieve in
26、 accordance with TestMethod E276 and shall be dried at 105 C to 110 C for a minimum of 1 h.10.Procedure10.1Transfer 0.50 g of the previously dried sample, weighed to the nearest 0.1 mg to a 30-mL iron crucible (Note 1Note 2) andadd8gofdryNa2O2(Note 23). Thoroughly mix the contents of the crucible an
27、d cover the mixture with an additional 1 g to 2gofNa2O2.10.2Cover the crucible with an iron or nickel cover and carefully fuse the contents at 600 C to 700 C, preferably in an electricmuffle furnace. After the mix has melted, fuse for several minutes at a low red heat while giving a slight rotary mo
28、tion to thecrucible to ensure complete decomposition.3Reagent Chemical, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by theAmerican Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd.,
29、 Poole Dorset, U. K., and the Reagent Chemicals, American Chemical SocietySpecifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by the American Chemical Society, see the United StatesPharmacopeia and National Formulary, U.S. Pharmaceutical
30、Convention, Inc.,Inc. (USPC), Rockville, MD.E342112NOTE12Ordinary iron crucibles which may contain significant amounts of chromium should be avoided. Crucibles made of ingot iron are satisfactory.NOTE2If about 0.2 g of very fine pulverized sugar charcoal is mixed with the Na3Only about5gofNa2O2, onl
31、y about5goftheperoxide is required.After heating for about 30 s, ignition of the charcoal takes place, and the crucible will suddenly become a dull red on the outside. The total time requiredto complete the fusion is about 2 min. By thus shortening the time for fusion and contact with the flux, the
32、life of the crucible is extended.10.2Place the cool crucible and cover in a 600-mL covered beaker, leach the melt with 150 mL of water, remove the crucibleand cover, and rinse. Boil 10 min to destroy the residual peroxide. Add to the cooled solution 60 mL of His required if about 0.2 g ofvery fine p
33、ulverized sugar charcoal is mixed with the Na2O2. After heating for about 30 s, ignition of the charcoal takes place, and the cruciblewill suddenly become a dull red on the outside. The total time required to complete the fusion is about 2 min. By shortening thetime for fusion and contact with the f
34、lux, the life of the crucible is extended.10.3Place the cool crucible and its cover into a 600-mLcovered beaker, leach the melt with 150 mLof water, remove the crucibleand cover, and rinse the crucible and cover into the beaker. Boil 10 min to destroy the residual peroxide.10.4Add to the cooled solu
35、tion 60 mL of H2SO4(1+1)and5mLofHNO3and boil for several minutes until any iron scalefrom the crucible is dissolved.10.5Add 15 mL of AgNO3solution, 2 drops of KMnO4solution (7.9), and 10 mL of (NHsolution (7.8), and 10 mL of (NH4)2S2O8solution and boil for 5 min.10.6Add 10 mL of NaCl solution and bo
36、il for 5 min to 10 min after the KMnO4or any MnO2has completely disappeared.10.37Cool, and if necessary, dilute with cold water to 350 mL, then add 3 mL to 5 mL of H3PO4(7.8). Add a measured excessof FeSO(7.7).10.8Add a measured excess of FeSO4(NH4)2SO46H2O. The point at which reduction is complete
37、can be detected by thedevelopment of deep green color. The FeSO4(NH4)2SO46H2O may be added either as the 0.2 N prepared solution (7.4) or aweighed amount of the salt (Note 34). Add 2 drops of orthophenanthroline ferrous sulfate (Ferroin)(ferroin) as an indicator.10.9Titrate the excess FeSO4(NH4)2SO4
38、6H2O with 0.2 N KMnO4solution (7.9). The end point is reached whenever the solutionbecomes clear green in color.NOTE34Approximately 70 mL of 0.2 N FeSO4(NH4)2SO46H2O solution of (7.4) containing 5.5 g of the salt is required for a chrome ore containing65%Cr2O3. (Note 1).11.Calculation11.1Calculate t
39、he percentage of chromium oxide content as follows:ChromiumoxideCr2O3!,%5A2B!3C30.02534/D3100 (1)ChromiumoxideCr2O3!,%5A2B!3C32.534D(1)where:A = millilitres of standard KMnO4solution (7.9) equivalent to the total amount of FeSO4(NH4)2SO46H2O added to the samplesolution,B = millilitres of standard KM
40、nO4solution (7.9) required to titrate the excess FeSO4(NH4)2SO46H2O,C = normality of standard KMnO4solution, andD = grams of sample used.grams of sample used (Note 1).12.Precision and Bias12.1PrecisionTable 1 indicates the precision of this test method between laboratories.12.2BiasNo information on
41、the bias of this test method is known. Accepted reference materials may not have been includedin the materials used in the interlaboratory study. Users of this test method are encouraged to employ accepted reference materials,if available, and to judge the bias of the method from the difference betw
42、een the accepted value for the chromium oxide contentand the mean value from interlaboratory testing of the reference material.TABLE 1 Precision DataAverageConcentration,A%RelativeStandard DeviationB, %Number ofParticipatingLaboratories51.52 0.21 442.11 0.19 5AEach conc valuent ration represents a d
43、ifferent kind of chrome ore.BRelative Standard Deviation, RSD, in thi (s test meth Nod is calculated asfollows:RSD5100/X!=(d2/n21!where:X= average concentration, %d = difference of the determination from the mean, andn = number of determinations).E34211313.Keywords13.1chromium ores; chromium oxide c
44、ontent13.1 chromium ores; chromium oxide content; permanganate titrimetry; titrimetryASTM International takes no position 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 th
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