1、Designation: D 1845 86 (Reapproved 2008)Standard Test Methods forChemical Analysis of Strontium Chromate Pigment1This standard is issued under the fixed designation D 1845; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods cover the chemi
3、cal analysis ofstrontium chromate pigment.1.2 The analytical procedures appear in the following order:SectionsStrontium by the Strontium Sulfate Method 7 to 10Chromium by the Thiosulfate Method 11 to 14Chloride Content 15Sulfate Content 16Moisture and Other Volatile Matter 17Coarse Particles 18Mass
4、Color and Tinting Strength 191.3 This values stated in SI units are to be considered thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address the safetyconcerns associated with its use. It is the responsibility of theuser of this standard to
5、establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D 185 Test Methods for Coarse Particles in PigmentsD 280 Test Methods for Hygroscopic Moisture (and OtherMatter Volatile Under the Test
6、Conditions) in PigmentsD 387 Test Method for Color and Strength of ChromaticPigments with a Mechanical MullerD 444 Test Methods for Chemical Analysis of Zinc YellowPigment (Zinc Chromate Yellow)D 1193 Specification for Reagent Water3. Significance and Use3.1 These test methods may be used to confirm
7、 the statedstrontium oxide and chromium oxide content of strontiumchromate.4. Apparatus4.1 Gooch crucible.4.2 Electric Furnace, capable of 800C.5. Purity of Reagents5.1 Reagent grade chemicals shall be used in all tests.Unless otherwise indicated, it is intended that all reagents shallconform to the
8、 specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications are available.3Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use, without lessening the accuracy ofthe determin
9、ation.5.2 Unless otherwise indicated, references to water shall beunderstood to mean Type II of Specification D 1193.6. Preparation of Sample6.1 Mix the sample thoroughly. Take a sufficient quantityfor chemical analysis and pass it through a No. 325 (4-m)sieve.STRONTIUM BY THE STRONTIUM SULFATEMETHO
10、D7. Reagents7.1 Acetic Acid (glacial).7.2 Ammonium Hydroxide (1+3)Mix 1 volume of con-centrated ammonium hydroxide (NH4OH, sp gr 0.90) with 3volumes of water.1These test methods are under the jurisdiction of ASTM Committee Paint andRelated Coatings, Materials, and Applications and are the direct res
11、ponsibility ofSubcommittee D01.31 on Pigment Specifications.Current edition approved Feb. 1, 2008. Published February 2008. Originallyapproved in 1961. Last previous edition approved in 2003 as D 1845 86 (2003).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Cust
12、omer 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 suggestions on the testing of reagents not
13、listed 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700,
14、West Conshohocken, PA 19428-2959, United States.7.3 Ethyl Alcohol, conforming to Formula No. 2B or No. 30of the U.S. Bureau of Alcohol, Tobacco, and Firearms.7.4 Hydrochloric Acid (1+1)Mix equal volumes of con-centrated hydrochloric acid (HCl, sp gr 1.19) and water.7.5 Sulfuric Acid (1+19)Mix 1 volu
15、me of concentratedsulfuric acid (H2SO4, sp gr 1.84) with 19 volumes of water.8. Procedure8.1 Weigh to 0.1 mg about 0.5 g of the sample into a400-mL beaker. Add 40 mL of HCl (1+1) and heat the solutionto dissolve the pigment. Add 40 mL of ethyl alcohol until thechromium is reduced, as this is indicat
16、ed by a dark colorationof the solution. Add to the solution 100 mL of water andsufficient NH4OH (1+3) to form a slight persistent precipitate.8.2 Add HCl dropwise until the precipitate just redissolves(Note 1). Heat the solution to just under boiling and add 20 mLof H2SO4(1+19). Add 100 mL of ethyl
17、alcohol and allow theprecipitate to settle for several hours or overnight.NOTE 1For a cleaner precipitate, add HCl until a pH of 2.0 is reached,instead of adding HCl dropwise until the precipitate is just dissolved. Thenadd 25 mL of acetic acid to minimize the tendency of the sulfate to forma comple
18、x with trivalent chromium. Finally, heat the solution, and addH2SO4(1 + 19).8.3 Filter the precipitate through a Gooch crucible that hasbeen previously dried to constant weight. Wash the precipitateseveral times with a solution of equal volumes of ethyl alcohol,water, and H2SO4(1+19). Dry the crucib
19、le in an oven and thenignite for12 h at 800C or until constant weight is attained(weight loss less than 0.1 mg). Cool and weigh the crucible.9. Calculation9.1 Calculate the percent of strontium oxide (SrO) asfollows:SrO, % 5 P 3 0.56416!/S 3 100where:P = SrSO4precipitate, g, andS = pigment specimen,
20、 g.0.56416 5molecular weight of SrOmolecular weight of SrSO45103.63163.7010. Precision10.1 Within LaboratoryThe usual difference between du-plicate runs performed by the same analyst is approximately0.2 % of the SrO content of the pigment tested.10.2 Between LaboratoriesThe average difference be-twe
21、en two determinations performed by different analysts indifferent laboratories is approximately 0.5 % of the SrOcontent of the pigment tested.CHROMIUM BY THE THIOSULFATE METHOD11. Reagents11.1 Hydrochloric Acid (1+5)Mix 1 volume of concen-trated hydrochloric acid (HCl, sp gr 1.19) with 5 volumes ofw
22、ater.11.2 Potassium Iodide Solution (150 g per L)Dissolve150 g of potassium iodide (KI) in water and dilute to 1 L.11.3 Sodium Thiosulfate Standard Solution (0.1 N)Dissolve 24.8 g of reagent grade Na2S2O35H2O in recentlyboiled water and dilute to 1 L with additional recently boiledwater. To standard
23、ize, pipet 25 mL of the standard potassiumdichromate solution (exactly 0.1000 N) into a 250-mL Erlen-meyer flask. Add 100 mL of water, 15 mL of potassium iodidesolution, and 15 mL of concentrated hydrochloric acid (sp gr1.19). Titrate the liberated iodine with sodium thiosulfatesolution until the re
24、ddish-brown color becomes quite faint.Add5 mL of starch solution and continue the titration dropwiseuntil the blue color changes to a pale green. Calculate thenormality of the sodium thiosulfate solution as follows:N 52.5000Mwhere:N = normality, andM = sodium thiosulfate solution, g.11.4 Starch Indi
25、cator SolutionMake a homogenous pasteof 10 g of soluble starch in cold water. Add to this 1 L ofboiling water, stir rapidly, and cool. Salicylic acid (1.25 g/L)may be added to preserve the indicator. If long storage isrequired, the solution should be kept in a refrigerator at 4 to10C (40 to 50F). Pr
26、epare fresh indicator when the end pointof the titration from blue to colorless or blue to light green failsto be sharp.12. Procedure12.1 Weigh accurately approximately 0.2 g of the sampleinto a 250-mL iodine flask. Add 50 mL of water and 50 mL ofHCl (1 + 5); swirl the flask to complete solution.Add
27、 20 mL ofKI solution and allow the solution to stand for several minutes.12.2 Titrate the liberated iodine with 0.1 N Na2S2O3solu-tion until the reddish brown iodine color becomes faint. Add 1mL of starch solution and continue the titration cautiously tothe end point which is easily discernible when
28、 the colorchanges from blue to a light green with no blue tinge.13. Calculation13.1 Calculate the percent of chromium as chromic oxide(CrO3) as follows:CrO3,%5 VN 3 0.03334!/S 3 100where:V =Na2S2O3solution required for titration of specimen,mL,N = normality of the Na2S2O3solution, andS = sample used
29、, g.14. Precision and Bias14.1 Within LaboratoriesThe usual difference betweenduplicate runs performed by the same analyst is approximately0.3 % of the CrO3content of the pigment tested.14.2 Between LaboratoriesThe average difference be-tween two determinations performed by different analysts indiff
30、erent laboratories is approximately 0.5 % of the CrO3content of the pigment tested.D 1845 86 (2008)20.0334 5molecular weight CrO21000 3 3 volume!599.991000 3 35 milliequivalent weightCHLORIDE CONTENT15. Procedure15.1 Determine the chloride content in accordance with TestMethods D 444.SULFATE CONTENT
31、16. Procedure16.1 Determine the sulfate content in accordance with theTest Methods D 444.MOISTURE AND OTHER VOLATILE MATTER17. Procedure17.1 Determine moisture and other volatile matter in accor-dance with Method A of Test Methods D 280.COARSE PARTICLES18. Procedure18.1 Determine the percentage of c
32、oarse particles in thepigment as received in accordance with Test Methods D 185.MASS COLOR AND TINTING STRENGTH19. Procedure19.1 Determine mass color and tinting strength in accor-dance with Test Method D 387.20. Keywords20.1 chromium; strontium chromate pigment; thiosulfatemethodASTM International
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