1、Designation: E314 16Standard Test Methods forDetermination of Manganese in Iron Ores by PyrophosphatePotentiometry and Periodate SpectrophotometryTechniques1This 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) 815Test Method B (Periodate (Spectrophotometric) 16221.2 Test Method A covers the determination of manganesein the range from 2.5 % to 15.0 %. Test Method B covers thedeter
4、mination of manganese in the range 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 asstandard. No other
5、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 the applica-bility of r
6、egulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E29 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 Material
7、sE135 Terminology Relating to Analytical Chemistry forMetals, Ores, and Related MaterialsE173 Practice for Conducting Interlaboratory Studies ofMethods for Chemical Analysis of Metals (Withdrawn1997)3E877 Practice for Sampling and Sample Preparation of IronOres and Related Materials for Determinatio
8、n of Chemi-cal Composition and Physical PropertiesE882 Guide for Accountability and Quality Control in theChemical Analysis LaboratoryE1601 Practice for Conducting an Interlaboratory Study toEvaluate the Performance of an Analytical Method3. Terminology3.1 DefinitionsFor definitions of terms used in
9、 these testmethods, refer to Terminology E135.4. Significance and Use4.1 This test method is intended to be used for compliancewith compositional specifications for manganese content iniron ores, concentrates, and agglomerates. It is assumed that allwho use these procedures will be trained analysts
10、capable ofperforming common laboratory procedures skillfully andsafely. It is expected that work will be performed in 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.
11、 Reagents and Materials5.1 Purity of ReagentsThe purity of the common chemicalreagents used shall conform to Practices E50. Special appara-tus and reagents required are located in separate sectionspreceding the procedure.6. Hazards6.1 For precautions to be observed in this method, refer toPractices
12、E50.1These 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 edition approved Nov. 1, 2016. Published
13、 December 2016. Originallyapproved in 1966. Last previous edition approved in 2015 as E314 10 (2015)1.DOI: 10.1520/E0314-16.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, r
14、efer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was develope
15、d in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organiziation Technical Barriers to Trade (TBT) Committee.17. Sampling and Sampl
16、e Preparation7.1 The gross sample shall be collected and prepared inaccordance with Practice E877.7.2 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.T
17、EST METHOD APYROPHOSPHATE(POTENTIOMETRIC) METHOD8. Summary of Test Method8.1 The test sample is decomposed by treatment with HCl,HNO3, 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 st
18、andardsolution of potassium permanganate. The end point is deter-mined potentiometrically.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 th
19、ese instruments can accept a variety ofelectrodes and therefore can be used also for potential 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 potentio
20、meter which makes the emf balancingoperation entirely automatic. Electrometer tube input is 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
21、read in pH directly, andpermit readings that are accurate to at least 6 0.01 pH unit. Forhigher 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 us
22、ed for pH measurements. These are called the referenceand indicator electrodes. By international 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 calome
23、lelectrode. It is most often used as a pencil-type unit that isimmersed directly in the solution, 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,
24、 but it ismore difficult to prepare than the saturated calomel electrode.The mercurous sulfate 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
25、quinhydrone and antimony-antimonous oxide electrodes are used to a much lesser extent.Combination 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 t
26、he meter and stored.When pH measurements are not being made the electrodesconnected to the 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 ti
27、me.10.2 Potentiometric Titration ApparatusInstruments fordetecting the end points in pH (acid-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 whe
28、n twodissimilar electrodes are placed in a solution there is a potentialdifference between 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
29、 may bedetermined by adding the titrant until the potential differenceattains a predetermined 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
30、necessary for potentiometric titrations becausethe absolute cell voltage needs to be known onlyapproximately, and variations of less than 1 mV are notsignificant. Such instruments should have a range of about1.5 V and a readability of about 1 mV. Many of the pH metersare also suitable for potentiome
31、tric titrations.10.2.2 The electrode system must consist of a referenceelectrode and an 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 titrat
32、ion; further, the indicatorelectrode must be one that will quickly come to equilibrium.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 thecorres
33、ponding potential differences are noted. By use ofestablished techniques the end point 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. This
34、technique is applicable to reasonably rapid reactions involvingstrong oxidants and reductants, 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 recor
35、ding of the titrationcurve on a strip chart, and the recording of the titrant end pointvolume on a tape. In the latter, an adjustable print-out delayprevents undertitrating when the reaction is slow.10.3 Magnetic StirrerUse of a TFE-fluorocarbon-coveredstirring bar is recommended.E314 16211. Reagent
36、s11.1 Hydrochloric Acid (sp gr 1.19)Concentrated.11.2 Hydrochloric Acid (1 + 1)Mix one volume 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.11.4 Hydrofluoric Acid (48 %)Concentrated
37、.11.5 Hydrogen Peroxide (3 %)Mix one volume of con-centrated hydrogen peroxide (H2O2, 30 %) with nine volumesof water.11.6 Nitric Acid (sp gr 1.42)Concentrated.11.7 Perchloric Acid (70 %).11.8 Potassium Permanganate, Standard Solution (0.1 N).11.8.1 PreparationDissolve 3.2 g of potassium perman-gana
38、te (KMnO4) in 1 L of water. Let stand in the dark for twoweeks. Filter, 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 a samp
39、le of so-dium 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 mLmin to
40、 35 mLmin, 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 addi
41、ng 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 to 0.05 mL.NOTE 3A 0.3000-g portion of sodium oxalate requires 44.77 mL ofKMnO4solution (0.1 N).NOTE 4If the KMnO
42、4solution 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.
43、1500 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 valan
44、ce change 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 0.05494
45、 (Mn equivalent of KMnO4in the (7 to 2) valence change).11.10 Sodium Carbonate (Na2CO3).11.11 Sodium Hydroxide Solution (200 gL)Dissolve200 g of NaOH in 500 mL to 600 mL of water and dilute to1L.11.12 Sodium Pyrophosphate (Na4P2O710H2O), SaturatedSolutionThis reagent shall be tested in the titration
46、 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 110 C (Note 6) for 1 h, cap the bottle, and cool toroom tempera
47、ture in a desiccator. Momentarily release the capto equalize pressure and weigh the capped bottle to the nearest0.0001 g. Repeat the drying and weighing until there is nofurther weight loss. Transfer the test sample to a 600-mLbeaker and reweigh the capped bottle to the nearest 0.0001 g.The differen
48、ce 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 water,add 20 mL of HCl, cover
49、, 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.12.2.1 At this point manganese, which may have separatedas manganese dioxide (MnO2), should be dissolved by thedropwise addition of H2O2. If any residue remains, dilute with50 mL of hot water and filter the solution through a medium-texture paper.Wash alternately with HCl (1 + 10) a
