1、Designation: D 3546 05Standard Test Method forFormic Acid in Glacial Acetic Acid1This standard is issued under the fixed designation D 3546; 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 par
2、entheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 oxidation with lead t
3、etraacetate.21.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 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
4、 off “to the nearestunit” in the last right-hand digit used in expressing thespecification limit, in accordance with the rounding-off methodof Practice E 29.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user o
5、f this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.5 For hazard information and guidance, see the suppliersMaterial Safety Data Sheets.2. Referenced Documents2.1 ASTM Standards:3D 1193 Specification for Reag
6、ent WaterE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis3. Summary of Test Method3.1 In an aqueous acetic acid solution each molecule
7、 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 end point.4
8、. 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 methyl alc
9、ohol) 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 grade chemi
10、cals 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 ascertained
11、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 D 1193.5.3 Lead Tetraacetate SolutionDis
12、solve 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 E 200.5.5 Starch Indicator SolutionPrepare the starch i
13、ndicatorsolution as described in Practice E 200.5.6 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 responsibil
14、ity ofSubcommittee D01.35 on Solvents, Plasticizers, and Chemical Intermediates.Current edition approved May 15, 2005. Published June 2005. Originallyapproved in 1976. Last previous edition approved in 1999 as D 3546 90 (1999).2Perlin, A. S., “Determination of Formic Acid by Oxidation with LeadTetra
15、acetate,” 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 Summary page onthe ASTM website.4R
16、eagent 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 the United States Pharmacopeia
17、and 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. Procedure6.1 Pipet 25 mL of the lea
18、d 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 formic acid:Formic Acid, % Speci
19、men 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 yellowprecipitate. This usually req
20、uires 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 repeat with a smaller specimen.7.
21、 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 = specific gravity of the sample a
22、t 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 % confi-dence level).9. Precision
23、 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-laboratory standard deviation was est
24、imatedto 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 level:9.1.1 RepeatabilityTwo
25、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 should beconsidered suspect i
26、f 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 measure “reducingsubstances, as for
27、mic 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(D 3546 90 (1999) that may impact the use of this standard.(1) Added reference to Practice E29 in 1.3 of the Scop
28、esection.(2) Added Practice E29to list of Referenced Documents.ASTM 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
29、 patent rights, and the riskof infringement of such rights, are entirely 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
30、 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 feel that your comments have not received a f
31、air 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 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).D3546052
