1、Designation: D3546 05 (Reapproved 2011)Standard Test Method forFormic Acid in Glacial Acetic Acid1This standard is issued under the fixed designation D3546; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of the formicacid (and other reducing substances) content of glacial aceticacid by oxidat
3、ion with lead tetraacetate.21.2 For purposes of determining conformance of an ob-served or a calculated value using this test method to relevantspecifications, test result(s) shall be rounded off “to the nearestunit” in the last right-hand digit used in expressing thespecification limit, in accordan
4、ce with the rounding-off methodof Practice E29.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 For hazard information and guidance, see the suppliersMaterial Safety Data Sheets.1.5 This standard does not purport to addre
5、ss 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 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1193 Specifica
6、tion for Reagent WaterE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE200 Practice for Preparation, Standardization, and Storageof Standard and Reagent Solutions for Chemical Analysis3. Summary of Test Method3.1 In an aqueous acetic acid solution ea
7、ch molecule offormic acid is oxidized to one molecule of carbon dioxide byreduction of one molecule of lead tetraacetate. The amount oflead tetraacetate remaining is then determined by addingpotassium iodide and titrating the liberated iodine with stan-dard sodium thiosulfate solution to the starch
8、end point.4. Significance and Use4.1 This test method is useful for determining the formicacid content of glacial acetic acid by chemical means.4.2 Low molecular weight organic acids (such as acetic andpropionic), aldehydes (including formaldehyde and acetalde-hyde), ketones, and alcohols (including
9、 methyl alcohol) do notinterfere with the test.4.3 Formic acid (and other reducing substances) may bepresent as a result of contamination during storage, distribu-tion, and manufacture. This test method may be used inassessing compliance with a specification.5. Reagents5.1 Purity of ReagentsReagent
10、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 Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first a
11、scertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.5.2 Purity of WaterUnless otherwise indicated referenceto water shall be understood to mean reagent water conformingto Type IV of Specification D1193.5.3 Lead Tetraacetate S
12、olutionDissolve completely 40.0g of sodium acetate in 1 L of glacial acetic acid and thendissolve 40.0 g of lead tetraacetate.5.4 Sodium Thiosulfate Standard Solution (0.1 N)Prepareand standardize 0.1 N sodium thiosulfate (Na2S2O3)asdescribed in Practice E200.5.5 Starch Indicator SolutionPrepare the
13、 starch indicatorsolution as described in Practice E200.5.6 Stopping SolutionDissolve 100 g of potassium iodideand 500 g of sodium acetate in 1 L of water.1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct res
14、ponsibility ofSubcommittee D01.35 on Solvents, Plasticizers, and Chemical Intermediates.Current edition approved Feb. 1, 2011. Published February 2011. Originallyapproved in 1976. Last previous edition approved in 2005 as D3546 05. DOI:10.1520/D3546-05R11.2Perlin, A. S., “Determination of Formic Aci
15、d by Oxidation with LeadTetraacetate,” Analytical Chemistry, Vol 26, 1954, pp. 10531054.3For 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 to the standards Document Summa
16、ry page onthe ASTM website.4Reagent 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 Ltd., Poole, Dorset, U.K., and t
17、he United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.6. Proced
18、ure6.1 Pipet 25 mL of the lead tetraacetate solution into each oftwo 500-mL Erlenmeyer flasks. Pipet the specimen (Note 1)into one of the flasks, swirl, and allow to stand for 20 to 30min. The second flask is the blank.NOTE 1The following are suggested specimen sizes for varyingconcentrations of for
19、mic acid:Formic Acid, % Specimen Size, mL0.0 to 0.10 250.10 to 0.30 100.30 to 0.60 50.60 to 1.00 31.00 to 2.00 22.00 to 3.00 16.2 Add to each flask a slight excess of the stopping solutionas indicated by the formation of the yellow lead iodideprecipitate. Add enough water just to dissolve the yellow
20、precipitate. This usually requires about 200 mL.6.3 Titrate the solution in both flasks with standard 0.1 NNa2S2O3solution to a pale yellow color. Add 1 mL of starchindicator and continue the titration until the blue color justdisappears. If the specimen titration is less than 10 mL, discardand repe
21、at with a smaller specimen.7. Calculation7.1 Calculate the weight percent of formic acid, A,asfollows:A 5B 2 V! 3 N 3 2.3D 3 S(1)where:B =Na2S2O3solution required for titration of the blank,mL,V =Na2S2O3solution required for titration of the speci-men, mL,N = normality of the Na2S2O3solution,D = spe
22、cific gravity of the sample at test temperature,S = specimen size, mL, and2.3 =equivalent weight of formic acid 23!310010008. Report8.1 Report the concentration of formic acid determined tothe nearest 0.001 weight % absolute. Duplicates that agreewithin 0.0031 % are acceptable for averaging (95 % co
23、nfi-dence level).9. Precision and Bias9.1 On the basis of an interlaboratory study of this testmethod in which operators in eight laboratories analyzed induplicate on each of two different days two samples of aceticacid with mean contents of 0.050 % and 0.172 % formic acid,the pooled within-laborato
24、ry standard deviation was estimatedto be 0.0016 % absolute with 13 df, and the between-laboratorystandard deviation was estimated to be 0.0105 % absolute with6 df. Based on these standard deviations, the following criteriashould be used for judging the acceptability of results at the95 % confidence
25、level:9.1.1 RepeatabilityTwo results, each the mean of dupli-cates, obtained by the same operator on different days shouldbe considered suspect if they differ by more than 0.005 %absolute.9.1.2 ReproducibilityTwo results, each the mean of dupli-cates, obtained by operators in different laboratories
26、should beconsidered suspect if they differ by more than 0.036 %absolute.9.2 BiasAny material or contaminant that will react withlead tetraacetate under the test conditions will affect the results.9.2.1 Various reducing materials may be present.As a result,this test method is sometimes used to measur
27、e “reducingsubstances, as formic acid.”10. Keywords10.1 formic acid content; glacial acetic acidSUMMARY OF CHANGESCommittee D01.35 has identified the location of selected changes to this standard since the last issue(D3546 90 (1999) that may impact the use of this standard.(1)Added reference to Prac
28、tice E29 in 1.2 of the Scope section. (2) Added Practice E29 to list of Referenced Documents.D3546 05 (2011)2ASTM 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
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30、proved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand 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
31、 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 is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual
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