1、Designation: D1845 86 (Reapproved 2014)Standard Test Methods forChemical Analysis of Strontium Chromate Pigment1This standard is issued under the fixed designation D1845; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods cover the che
3、mical 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 18Mas
4、s 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 t
5、o establish appropriate safety and healthpractices and determine the applicability of regulatory limita-tions prior to use.2. Referenced Documents2.1 ASTM Standards:2D185 Test Methods for Coarse Particles in PigmentsD280 Test Methods for Hygroscopic Moisture (and OtherMatter Volatile Under the Test
6、Conditions) in PigmentsD387 Test Method for Color and Strength of ChromaticPigments with a Mechanical MullerD444 Test Methods for Chemical Analysis of Zinc YellowPigment (Zinc Chromate Yellow)D1193 Specification for Reagent Water3. Significance and Use3.1 These test methods may be used to confirm th
7、e 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 sp
8、ecifications 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 determinati
9、on.5.2 Unless otherwise indicated, references to water shall beunderstood to mean Type II of Specification D1193.6. 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 SULFATEMETHOD7.
10、Reagents7.1 Acetic Acid (glacial).7.2 Ammonium Hydroxide (1+3)Mix 1 volume of concen-trated ammonium hydroxide (NH4OH, sp gr 0.90) with 3volumes of water.1These test methods are under the jurisdiction of ASTM Committee D01 onPaint and Related Coatings, Materials, and Applications and are the directr
11、esponsibility of Subcommittee D01.31 on Pigment Specifications.Current edition approved Dec. 1, 2014. Published December 2014. Originallyapproved in 1961. Last previous edition approved in 2008 as D1845 86 (2008).DOI: 10.1520/D1845-86R14.2For referenced ASTM standards, visit the ASTM website, www.as
12、tm.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 suggestions on
13、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.Copyright ASTM International, 100 Barr H
14、arbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States17.3 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 Sulf
15、uric Acid (1+19)Mix 1 volume 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 r
16、educed, as this is indicated 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
17、+19). Add 100 mL of ethyl 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 t
18、he sulfate to forma complex 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 H
19、2SO4(1+19). Dry the crucible 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 30.56416!/S# 3100where:P = SrSO4precipitate, g,
20、 andS = pigment specimen, 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
21、average difference be-tween 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
22、 1.19) with 5 volumes ofwater.11.2 Potassium Iodide Solution (150 g per L)Dissolve 150g 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
23、 boiledwater. To standardize, 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 thiosul
24、fatesolution until the reddish-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 sol
25、ution, g.11.4 Starch Indicator 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 a
26、t 4 to10C (40 to 50F). Prepare 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
27、 to complete solution.Add 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 i
28、s easily discernible when 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 30.03334!/S# 3100where:V =Na2S2O3solution required for titration of specimen,mL,N = normality of the Na2S2O3solu
29、tion, andS = sample used, 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 d
30、ifferent analysts inD1845 86 (2014)2different laboratories is approximately 0.5 % of the CrO3content of the pigment tested.0.0334 5molecular weight CrO21000 33 volume!599.991000 335milliequivalent weightCHLORIDE CONTENT15. Procedure15.1 Determine the chloride content in accordance with TestMethods D
31、444.SULFATE CONTENT16. Procedure16.1 Determine the sulfate content in accordance with theTest Methods D444.MOISTURE AND OTHER VOLATILE MATTER17. Procedure17.1 Determine moisture and other volatile matter in accor-dance with Method A of Test Methods D280.COARSE PARTICLES18. Procedure18.1 Determine th
32、e percentage of coarse particles in thepigment as received in accordance with Test Methods D185.MASS COLOR AND TINTING STRENGTH19. Procedure19.1 Determine mass color and tinting strength in accor-dance with Test Method D387.20. Keywords20.1 chromium; strontium chromate pigment; thiosulfatemethodASTM
33、 International takes no position respecting the validity 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 ent
34、irely their own responsibility.This standard is subject 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 standardsan
35、d should be addressed to ASTM International Headquarters. 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 o
36、n Standards, at the address 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 Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 86 (2014)3
