1、Designation: E314 10Standard Test Methods forDetermination of Manganese in Iron Ores by Pyrophosphate(Potentiometric) and Periodate (Photometric) Techniques1This standard is issued under the fixed designation E314; the number immediately following the designation indicates the year oforiginal adopti
2、on or, in the case of 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. Scope1.1 These test methods cover the determination of manga-nese in iron ores, con
3、centrates, and agglomerates. The follow-ing two test methods are included:SectionsTest Method A (Pyrophosphate (Potentiometric) 8-15Test Method B (Periodate (Photometric) 16-221.2 Test Method A covers the determination of manganesein the concentration range from 2.5 % to 15.0 %. Test MethodB covers
4、the determination of manganese in the concentrationrange of 0.01 % to 5.00 %.NOTE 1The lower limit for this test method is set at 50 % relativeerror for the lowest grade material tested in the interlaboratory study inaccordance with Practice E1601.1.3 The values stated in SI units are to be regarded
5、 asstandard. No other units of measurement are included in thisstandard.1.4 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 t
6、he applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E50 Practices for Apparatus, Reagents, and Safety Consid-erations for Chemical Analysis of Metals, Ores, andRelated MaterialsE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Rela
7、ted MaterialsE173 Practice for Conducting Interlaboratory Studies ofMethods for Chemical Analysis of Metals3E877 Practice for Sampling and Sample Preparation of IronOres and Related Materials for Determination of ChemicalCompositionE882 Guide for Accountability and Quality Control in theChemical Ana
8、lysis LaboratoryE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method3. Terminology3.1 DefinitionsFor definitions of terms used in these testmethods, refer to Terminology E135.4. Significance and Use4.1 This test method is intended to be used for c
9、ompliancewith compositional specifications for manganese content iniron ores, concentrates, and agglomerates. It is assumed that allwho use these procedures will be trained analysts capable ofperforming common laboratory procedures skillfully andsafely. It is expected that work will be performed in
10、a properlyequipped laboratory and that proper waste disposal procedureswill be followed. Appropriate quality control practices must befollowed such as those described in Guide E882.5. Reagents and Materials5.1 Purity and Concentration of ReagentsThe purity andconcentration of the common chemical rea
11、gents used shallconform to Practices E50. Special apparatus and reagentsrequired are located in separate sections preceding the proce-dure.6. Hazards6.1 For precautions to be observed in this method, refer toPractices E50.7. Sampling and Sample Preparation7.1 The gross sample shall be collected and
12、prepared inaccordance with Practice E877.1These test methods are under the jurisdiction of ASTM Committee E01 onAnalytical Chemistry for Metals, Ores, and Related Materials and are the directresponsibility of Subcommittee E01.02 on Ores, Concentrates, and Related Metal-lurgical Materials.Current edi
13、tion approved June 15, 2010. Published August 2010. Originallyapproved in 1966. Last previous edition approved in 2005 as E314 00 (2005).DOI: 10.1520/E0314-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of
14、ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn. The last approved version of this historical standard is referencedon www.astm.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United
15、 States.7.2 The analytical sample shall be pulverized to pass a No.100 (150-m) sieve.NOTE 2To facilitate decomposition some ores, such as specularhematites, may require grinding to pass a No. 200 (75-m) sieve.TEST METHOD APYROPHOSPHATE(POTENTIOMETRIC) METHOD8. Summary of Test Method8.1 The test samp
16、le is decomposed by treatment with HCl,NHO3, HF, and HClO4.After the addition of sodium pyrophos-phate and the adjustment of the acidity, the manganese isdetermined by oxidation to trivalent manganese with a standardsolution of potassium permanganate. The end point is deter-mined potentiometrically.
17、9. Interferences9.1 Provision has been made for the removal of chromiumwhich under some conditions is an interfering element.10. Apparatus10.1 pH MeterA number of pH meters are commerciallyavailable. Many of these instruments can accept a variety ofelectrodes and therefore can be used also for poten
18、tial mea-surements.Although both line- and battery-operated pH metersare manufactured, the former is recommended for laboratorywork because this type of pH meter contains an electronic ortransistorized potentiometer which makes the emf balancingoperation entirely automatic. Electrometer tube input i
19、s usedon both the electronic and transistorized pH meters.10.1.1 The pH meter must have electrode standardization(or asymmetry potential) and manual or automatic temperaturecompensation controls. The dial must read in pH directly, andpermit readings that are accurate to at least 6 0.01 pH unit. Forh
20、igher accuracies it is recommended that a pH meter with anexpanded scale be used.10.1.2 Because there is no accurate method for determiningthe absolute potential of an individual electrode, two electrodesare used for pH measurements. These are called the referenceand indicator electrodes. By interna
21、tional agreement the hy-drogen electrode is the standard indicator electrode for pH, butis inconvenient to use and subject to several limitations. Themost widely used reference electrode is the saturated calomelelectrode. It is most often used as a pencil-type unit that isimmersed directly in the so
22、lution, but may also be utilized asan external cell (to prevent possible contamination) contactingthe solution by means of a salt bridge. The silver-silverchloride reference electrode is also convenient to use, but it ismore difficult to prepare than the saturated calomel electrode.The mercurous sul
23、fate reference electrode may be used insolutions in which the chloride ions that diffuse out of thecalomel cell might be harmful.10.1.3 The most commonly employed indicator electrode isthe glass electrode. The quinhydrone and antimony-antimonous oxide electrodes are used to a much lesser extent.Comb
24、ination electrodes containing both the indicator andreference units are also available. The tips of the electrodescontaining solutions must be covered with rubber caps whenthe electrodes are disconnected from the meter and stored.When pH measurements are not being made the electrodesconnected to the
25、 pH meter should be kept in a beakercontaining water. Prior to measuring the pH of a solution theelectrodes must be thoroughly washed with water especially ifthey have been left standing for a long period of time.10.2 Potentiometric Titration ApparatusInstruments fordetecting the end points in pH (a
26、cid-base), oxidation-reduction,precipitation, and complexation titrations consist of a pair ofsuitable electrodes, a potentiometer, a buret, and a motor-driven stirrer. Titrations are based on the fact that when twodissimilar electrodes are placed in a solution there is a potentialdifference between
27、 them. This potential difference depends onthe composition of the solution and changes as the titrant isadded. A high-impedance electronic voltmeter follows thechanges accurately. The end point of the titration may bedetermined by adding the titrant until the potential differenceattains a predetermi
28、ned value or by plotting the potentialdifference versus the titrant volume, the titrant being addeduntil the end point has been passed.10.2.1 An elaborate or highly sensitive and accurate poten-tiometer is not necessary for potentiometric titrations becausethe absolute cell voltage needs to be known
29、 only approxi-mately, and variations of less than 1 MV are not significant.Such instruments should have a range of about 1.5 V and areadability of about 1 MV. Many of the pH meters are alsosuitable for potentiometric titrations.10.2.2 The electrode system must consist of a referenceelectrode and an
30、indicator electrode. The reference electrodemaintains a constant, but not necessarily a known or reproduc-ible potential during the titration. The potential of the indicatorelectrode does change during the titration; further, the indicatorelectrode must be one that will quickly come to equilibrium.
31、Aplatinum indicator electrode and reference electrode are re-quired for this method.10.2.3 Initially, a titration of the constituent in question isperformed manually, and the volumes of titrant added and thecorresponding potential differences are noted. By use ofestablished techniques the end point
32、potential is determined.For the analytical determinations, titration may be continued toa preset potential, the end point being signaled by a null meter,with or without automatic termination of the titration. Thistechnique is applicable to reasonably rapid reactions involvingstrong oxidants and redu
33、ctants, precipitates not more solublethan silver chloride, and ionization constants greater than thatof boric acid.10.2.4 Other techniques may be used for both slow and fastreactions. These include automatic recording of the titrationcurve on a strip chart, and the recording of the titrant end point
34、volume on a tape. In the latter, an adjustable print-out delayprevents undertitrating when the reaction is slow.10.3 Magnetic StirrerUse of a TFE-fluorocarboncoveredstirring bar is recommended.11. Reagents11.1 Hydrochloric Acid (sp gr 1.19)Concentrated HCl.11.2 Hydrochloric Acid (1 + 1)Mix one volum
35、e of con-centrated HCl (sp gr 1.19) with one volume of water.11.3 Hydrochloric Acid (1 + 10)Mix one volume of con-centrated HCl (sp gr 1.19) with ten volumes of water.E314 10211.4 Hydrofluoric Acid (48 %)Concentrated HF.11.5 Hydrogen Peroxide (3 %)Mix one volume of con-centrated hydrogen peroxide (H
36、2O2, 30 %) with nine volumesof water.11.6 Nitric Acid (sp gr 1.42)Concentrated HNO3.11.7 Perchloric Acid (70 %)(HClO4).11.8 Potassium Permanganate, Standard Solution (0.1 N).11.8.1 PreparationDissolve 3.2 g of potassium perman-ganate (KMnO4) in 1 L of water. Let stand in the dark for twoweeks. Filte
37、r, without washing, through a Gooch crucible or afine porosity fritted-glass crucible. Avoid contact with rubberor other organic material. Store in a dark-colored glass-stoppered bottle.11.8.2 StandardizationDry a portion of the National In-stitute of Standards and Technology (NIST) standard sample
38、ofsodium oxalate at 105 C. Transfer 0.3000 g of the sodiumoxalate to a 600-L beaker. Add 250 mL of H2SO4(5 + 95)previously boiled for 10 min to 15 min and then cooled to27 C 6 3 C, and stir until the oxalate has dissolved. Add39 mL to 40 mL (Note 3) of the KMnO4solution, at a rate of25 mL/min to 35
39、mL/min, while stirring slowly. Let stand untilthe pink color disappears (about 45 s) (Note 4). Heat to 55 Cto 60 C and complete the titration by adding KMnO4solutionuntil a faint pink color persists for 30 s. Add the last 0.5 mL to1 mL dropwise, allowing each drop to become decolorizedbefore adding
40、the next drop. To determine the blank: Titrate250 mL of H2SO4(5 + 95), treated as above, with KMnO4solution to a faint pink color. The blank correction is usuallyequivalent to 0.03 mL 3 0.05 mL.NOTE 3A 0.3000-g portion of sodium oxalate requires 44.77 mL ofKMnO4solution (0.1 N).NOTE 4If the KMnO4sol
41、ution is too strong, the pink color will notfade at this point; begin again, adding a few millilitres less of the KMnO4solution.11.9 Potassium Permanganate, Standard Solution (0.05 N)(Note 5)Dilute one volume of 0.1 N potassium permangan-ate solution with one volume of water. Standardize using0.1500
42、 g of sodium oxalate as described under 11.8.2. Confirmthe standardization against an ore of known manganese contentby carrying the known sample through all steps of theprocedure.NOTE 5The 0.05 normality of the potassium permanganate (KMnO4)solution used (1.5803 g/L) is based on the usual valance ch
43、ange ofmanganese in acid solution from 7 to 2. In the test method described, themanganese in the sample is oxidized from Mn (II) to Mn (III) while theKMnO4is reduced from Mn (III) to Mn (VII). The factor 0.04395mentioned in Section 13, therefore, is based on the following calculation:45 3 0.05494 (M
44、n equivalent of KMnO4in the (7 to 2) valence change).11.10 Sodium Carbonate (Na2CO3).11.11 Sodium Hydroxide Solution (200 g/L)Dissolve200 g of sodium hydroxide (NaOH) in 500 mL to 600 mL ofwater and dilute to 1 L.11.12 Sodium Pyrophosphate (Na4P2O710H2O), SaturatedSolutionThis reagent shall be teste
45、d in the titration of aknown amount of manganese. Only lots which rapidly providesteady potentials shall be used.12. Procedure12.1 Transfer approximately 0.5000 g of prepared sample toa small dry weighing bottle and place in a drying oven. Afterdrying at 105 C to 110 C (Note 6) for 1 h, cap the bott
46、le, andcool to room temperature in a desiccator. Momentarily releasethe cap to equalize pressure and weigh the capped bottle to thenearest 0.0001 g. Repeat the drying and weighing until there isno further weight loss. Transfer the test sample to a 600-mLbeaker and reweigh the capped bottle to the ne
47、arest 0.0001 g.The difference between the two weights is the weight of the testsample.NOTE 6Most ores yield their hygroscopic moisture at the specifiedtemperature. However, in the case of some ores, higher drying tempera-tures may be required.12.2 Moisten the test sample with a few millilitres of wa
48、ter,add 20 mL of HCl, cover, and heat below boiling. When allsoluble minerals are decomposed, add 10 mL of HNO3,4mLto 5 mL of HF, and 15 mL of HClO4and evaporate without acover to copious fumes of HClO4. Cool, and rinse down thesides of the beaker and dissolve the salts in 10 mL of water(Note 7). Co
49、ver and again evaporate to fumes HClO4and fumestrongly for 1 min. Withdraw the cover slightly and volatilizeany chromium present by the drop-wise addition of HCl. Whenchromyl chloride has been expelled, as indicated by theabsence of orange vapor on the addition of HCl, replace thecover and evaporate to about 3 mLor until the salts form on thebottom of the beaker. Cool, add 10 mL of HCl (1 + 1) and1mLofH2O2, and boil for about 5 min.NOTE 7At this point manganese, which may have separated asmanganese dioxide (MnO2), should be dissolved by the drop
