1、Designation: D3872 05 (Reapproved 2011)Standard Test Method forFerrous Iron in Iron Oxides1This standard is issued under the fixed designation D3872; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A numb
2、er 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 quantitative determinationof ferrous oxide (FeO) by oxidation of ferrous iron (Fe+)inanacid solution to the fer
3、ric state (Fe+) and titration withpotassium dichromate using diphenylamine as the indicator.1.2 This test method is applicable to synthetic black ironoxide, natural black iron oxide, magnetite or brown iron oxidewhere part of the iron content is present in the ferrous state(Note 1). It is applicable
4、 to iron oxides where the ferrous ironcontent ranges from 50 to 0.20 %.NOTE 1Natural iron oxides and magnetite may contain traces ofmetallic iron that will be combined with and analyzed as FeO.1.3 This standard does not purport to address the safetyconcerns if any, problems associated with its use.
5、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 use.2. Referenced Documents2.1 ASTM Standards:2D50 Test Methods for Chemical Analysis of Yellow, Or-ange, Red, and Brown Pigm
6、ents Containing Iron andManganeseD280 Test Methods for Hygroscopic Moisture (and OtherMatter Volatile Under the Test Conditions) in PigmentsD769 Specification for Black Synthetic Iron OxideD1193 Specification for Reagent WaterD3722 Specification for Natural Red and Brown Iron OxidePigmentsD3724 Spec
7、ification for Synthetic Brown Iron Oxide Pig-ment3. Significance and Use3.1 This test method may be used for production qualitycontrol or specification acceptance.4. Apparatus4.1 The digestion apparatus consists of a standard 500-mLErlenmeyer flask fitted with a two-hole rubber stopper andglass tubi
8、ng, as shown in Fig. 1, to provide for the introductionof the inert gas and vent for gas and digestion fumes.5. Reagents5.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Comm
9、it-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.5.2 Purity of WaterUnl
10、ess otherwise indicated, referencesto water shall be understood to mean Type II of SpecificationD1193.5.3 Diphenylamine IndicatorDissolve1gofdiphenylam-ine in 100 mL of concentrated (H2SO4) (sp gr 1.84).5.4 Hydrochloric Acid (1+1)Dilute concentrated hydro-chloric acid (HCl, sp gr 1.19) with an equal
11、 volume of reagentwater.5.5 Iron Ore, Standard, Sibley No. 27-f.45.6 Potassium Dichromate, Standard Solution (0.1 N)Dissolve 4.904 g of K2Cr2O7in water and dilute to 1 L.Standardize against National Institute of Standards and Tech-nology standard sample No. 27f of Sibley iron ore. Calculatethe Fe fa
12、ctor in grams per millilitre for the solution as:1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.31 on Pigment Specifications.Current edition approved June 1, 2011. Publish
13、ed June 2011. Originallyapproved in 1979. Last previous edition approved in 2005 as D3872 - 05. DOI:10.1520/D3872-05R11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer
14、 to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH
15、Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4May be secured from National Institute of Standards and Technology, Depart-ment of Commerce, Washington, DC 20234. Other recognized primary ironstandard may
16、be substituted.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Fe 5 W/V1(1)where:W = weight of Fe in the standard iron ore (not thesolution, as there is none), andVV1=K2Cr2O7required for titration of standard, mL.5.7 Sulfuric-Phospho
17、ric Acid SolutionPrepare by care-fully adding 600 mL of concentrated sulfuric acid (H2SO4) (spgr 1.84) to 800 mL of water while stirring, then add 600 mL ofphosphoric acid (85 to 87 %) mixing thoroughly. Cool andstore.6. Preparation of Sample (Note 2)6.1 Mix the sample thoroughly and take a represen
18、tativeportion for the analysis. Exercise care at all times to preventoxidation of the Fe+iron to the Fe+state (Note 2). Grindnatural iron oxides or natural magnetites to 100 % minus 100mesh.6.2 Finely divided synthetic black iron oxides if not care-fully dried can oxidize so that part of the Fe+iron
19、 is convertedto Fe+. For this reason moisture should be determined on aseparate specimen or by Test Methods D280, Part B. Vacuumdrying at temperatures not exceeding 65C is recommended.NOTE 2Coarsely ground natural iron oxides and magnetite are veryslow to dissolve. Exercise care in grinding oxides c
20、ontaining ferrous ironto avoid generating heat, as additional grinding could oxidize ferrous toferric iron.7. Procedure7.1 Weigh 0.5 g of oxide to 1 mg and transfer to the 500-mLErlenmeyer flask. Wash down the sides of the flask with 15 mLof water.7.2 Attach the stopper with funnel and the gas deliv
21、ery tubeto the flask. Open the CO2valve until a gentle stream of gasflows through the flask. Nitrogen may be substituted.7.3 Add 15 mL of 1 + 1 HCl (1+1). Digest on an asbestospad on the hot plate at just below boiling temperature untilcompletely dissolved or there is no further reaction (Note 3).Fi
22、nely divided synthetic black or brown oxides usually require5 to 10 min but natural oxides or magnetites may requireconsiderably longer.NOTE 3Synthetic black iron oxides may contain small amounts ofcarbon black to increase tint strength. Carbon black will not dissolveduring the digestion step and sh
23、ould not be confused with the soluble ironoxide.7.4 Remove the flask from the hot plate and add 30 mL ofsulfuric-phosphoric acid solution.Add 60 mLof water and coolin the water bath for 5 min.7.5 Remove the CO2apparatus and add 5 drops of thediphenylamine indicator. Titrate with the standard potassi
24、umFIG. 1 Digestion ApparatusD3872 05 (2011)2dichromate solution. The end point is sharp with a color changefrom green to purple. Avoid going past the end point.8. Calculations8.1 The percent FeO or Fe+in the unknown sample arecalculated by using Eq 1 or Eq 2.where:W = weight of Fe in standard soluti
25、on, g, andV = volume of potassium dichromate solution, mL.% FeO 5V 3 F 3 1.2865 3 100S(2)where:F = Fe factor defined by Eq 1, andS = specimen weight, g.%Fe115V 3 F 3 100S(3)1.2865 5molecular weight of FeOmolecular weight of Fe571.8555.8478.2 Report results to 0.1 %.9. Precision and Bias9.1 The preci
26、sion statements are based on an interlaboratorystudy of the method in which operators in seven laboratoriesanalyzed in duplicate on two days two commercial syntheticblack iron oxides containing 20 and 23 % ferrous iron oxide.The within-laboratory standard deviation was found to be0.235 for the first
27、 material and 0.05 for the second, each with7df. The between-laboratory standard deviations were 0.061and 0.058, respectively, each with 6 df. Based on the pooledstandard deviations, the following criteria should be used forjudging the acceptability of results at the 95 % confidencelevel:9.1.1 Repea
28、tabilityTwo results, each the mean of dupli-cate determinations, obtained by the same operator on differentdays should be considered suspect if they differ by more than0.5 % absolute at FeO contents of 20 to 25 %.9.1.2 ReproducibilityTwo results, each the mean of dupli-cate determinations, obtained
29、by operators in different labora-tories should be considered suspect if they differ by more than0.8 % absolute at FeO contents of 20 to 25 %.9.2 BiasBias has not been determined.10. Keywords10.1 ferrous iron content; iron oxides; ferrous iron content;pigment; iron oxidesASTM International takes no p
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33、ss shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D3872 05 (2011)3
