1、Designation: D 3872 05Standard Test Method forFerrous Iron in Iron Oxides1This standard is issued under the fixed designation D 3872; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parenthese
2、s 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 quantitative determinationof ferrous oxide (FeO) by oxidation of ferrous iron (Fe+)inanacid solution to the ferric state (Fe+)
3、 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 to iron oxides
4、 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. It is therespon
5、sibility 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:2D 50 Test Methods for Chemical Analysis of Yellow, Or-ange, Red, and Brown Pigments Containin
6、g Iron andManganeseD 280 Test Methods for Hygroscopic Moisture (and OtherMatter Volatile Under the Test Conditions) in PigmentsD 769 Specification for Black Synthetic Iron OxideD 1193 Specification for Reagent WaterD 3722 Specification for Natural Red and Brown IronOxide PigmentsD 3724 Specification
7、 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 tubing, as sh
8、own 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 Commit-tee on
9、 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 WaterUnless other
10、wise indicated, referencesto water shall be understood to mean Type II of SpecificationD 1193.5.3 Diphenylamine IndicatorDissolve1gofdipheny-lamine 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 volume
11、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 factor in
12、grams per millilitre for the solution as: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.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, an
13、d Applications and is the direct responsibility ofSubcommittee D01.31 on Pigment Specifications.Current edition approved Sept. 1, 2005. Published September 2005. Originallyapproved in 1979. Last previous edition approved in 1999 as D 3872 86 (1999).2For referenced ASTM standards, visit the ASTM webs
14、ite, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For sugg
15、estions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH 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
16、 Institute of Standards and Technology, Depart-ment of Commerce, Washington, DC 20234. Other recognized primary ironstandard may be substituted.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.7 Sulfuric-Phosphoric Acid SolutionPrep
17、are 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 representativeportion for the
18、 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 is convertedto Fe+.
19、For this reason moisture should be determined on aseparate specimen or by Test Methods D 280, 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 containing ferrous ir
20、onto 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 delivery tubeto the flask
21、. 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).Finely divided synthet
22、ic 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 should not be confused
23、 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 potassiumdichromate solutio
24、n. 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 2 or Eq 3.FIG. 1 Digestion ApparatusD3872052where:W = weight of Fe in standard solution, g, andV = volume of pota
25、ssium 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 precision statements are based on
26、 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 material and 0.05 for the s
27、econd, 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 RepeatabilityTwo results, each th
28、e 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 by operators in different la
29、bora-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 position respecting the valid
30、ity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subje
31、ct to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquart
32、ers. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard
33、 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).D3872053
