1、Designation: D2191 06 (Reapproved 2012)Standard Test Method forAcetaldehyde Content of Vinyl Acetate1This standard is issued under the fixed designation D2191; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. 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 tracequantities of acetaldehyde, in the range from 0.00 to 0.05 %,contained in 99 %
3、 grade vinyl acetate.1.2 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 accordance with
4、 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 Sheet.1.5 This standard does not purport to address all o
5、f 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. For specific hazardstatements see Section 8.2. Referenced Documen
6、ts2.1 ASTM Standards:2D1193 Specification for Reagent WaterE29 Practice for Using Significant Digits in Test Data toDetermine Conformance with Specifications3. Summary of Test Method3.1 The acetaldehyde present in the specimen is reactedwith a measured excess of sodium bisulfite. The amount ofsodium
7、 bisulfite consumed, determined by titrating the excesswith a standard iodine solution, is a measure of the acetalde-hyde present in the vinyl acetate.4. Significance and Use4.1 This test method provides a measurement of acetalde-hyde content in vinyl acetate. The results of these measure-ments can
8、be used for specification acceptance.5. Interference5.1 Ketones and other aldehydes, if present, cause a positiveinterference.6. Apparatus6.1 Buret, 50-mL capacity, graduated in 0.1-mL subdivi-sions, with a funnel or flared top and a ground-glass stopcock.6.2 Erlenmeyer Flask, 500-mL capacity, glass
9、-stoppered.6.3 Pipet, 50-mL capacity.6.4 Pipet, 100-mL capacity.7. Reagents7.1 Purity of ReagentsUnless otherwise indicated, it isintended that all reagents shall conform to the specifications ofthe Committee onAnalytical Reagents of theAmerican Chemi-cal Society, where such specifications are avail
10、able.3Othergrades may be used provided that it is first ascertained that thereagent is of sufficiently high purity to permit its use withoutlessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as defin
11、edby Type IV of Specification D1193.7.3 Iodine, Standard Solution (0.1 N)Dissolve 35.0 g ofpotassium iodide (KI) and 13.0 g of resublimed iodine in water,and dilute to 1 L with water. Store this solution in a dark bottleand standardize each day, as required, against a standard 0.1 Nsodium thiosulfat
12、e (Na2S2O3) solution. (See standardizationprocedure, 9.3 and 9.4.)1This test method is under the jurisdiction of ASTM Committee D01 on Paintand Related Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.35 on Solvents, Plasticizers, and Chemical Intermediates.C
13、urrent edition approved June 1, 2012. Published July 2012. Originally approvedin 1963. Last previous edition approved in 2006 as D2191 06. DOI: 10.1520/D2191-06R12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Boo
14、k 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 notlisted by the American Chemical Society, see An
15、alar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Dri
16、ve, PO Box C700, West Conshohocken, PA 19428-2959. United States17.4 Potassium Iodate (KIO3), primary standard.7.5 Sodium Bisulfite Solution (0.44 %)Dissolve 4.4 g ofsodium metabisulfite (Na2S2O5) in 1 L of water. This solutionshould be prepared fresh daily or just before using.7.6 Sodium Thiosulfat
17、e, Standard Solution(0.1 N)Weighto 0.1 g 24.8 g of sodium thiosulfate (Na2S2O35H2O) crystalsand dissolve in 500 mL of water. Dilute this solution to 1 Lwith water. Add 0.5 mL of chloroform per litre of solution asa preservative, and store in a clean dark bottle. This solutionshould be standardized w
18、eekly, as required, against potassiumiodate (KIO3). (See standardization procedure, 9.1 and 9.2.)7.7 Starch IndicatorMake a paste of 6 g of powderedsoluble starch in water, and dilute to 1 L with water, stirring toproduce a suspension. While stirring, add 20 g of potassiumhydroxide (KOH) pellets, an
19、d continue stirring until the KOHis dissolved. Let stand for 2 h and add 27.5 mL of hydrochloricacid (HCl). Adjust the mixture to a pH of 6.0 6 0.1 by addingsmall increments of HCl or KOH as required. Add 6 mL ofglacial acetic acid as a preservative.7.8 Sulfuric Acid (1 N)Place approximately 700 to
20、800mL of water in a 1-L volumetric flask. Add slowly and withconstant stirring 27.2 mL of concentrated sulfuric acid (H2SO4,sp gr 1.84). Allow the solution to cool to room temperature,and adjust the volume to the 1-L mark with additional water.8. Hazards8.1 Vinyl acetate is flammable and hazardous;
21、use specialprecautions when handling it. Avoid eye and skin contact andthe inhalation of its vapors.9. Standardization9.1 To standardize the 0.1 N Na2S2O3solution, first dry for6 h approximately3goftheKIO3primary standard in a dryingoven maintained at a temperature of 110 6 5C. Place the driedKIO3in
22、 a desiccator until cool. Weigh 0.14 to 0.15 g of thedried KIO3to 0.1 mg, and transfer to a 250-mL Erlenmeyerflask. Add 25 mL of water to the flask to dissolve the KIO3.Tothis solution, add2gofKIcrystals and 10 mL of the 1 NH2SO4, and thoroughly mix. Fill a 50-mL buret with theNa2S2O3solution to be
23、standardized and titrate the KIO3solution until the brown color of the iodine has been reduced toa pale yellow color. At this point, add 0.5 mL of the starchindicator, and continue the titration until the color changessharply from blue to colorless.NOTE 1When titrating excess iodine with sodium thio
24、sulfate, thestarch indicator should be added only when near the end point as noted bythe fading of the brown color of the iodine. Starch reacts with iodine in thepresence of iodide to form an intensely blue color absorption complex,and if added to a solution containing free iodine, a stable complex
25、isformed, that would give erroneous results.9.2 Calculate the normality N of the Na2S2O3solution asfollows:N 5 W 3 P!/V 30.035669!where:W = weight of KIO3used, gP = correction for purity of KIO3standard, andV = volume of Na2S2O3required for titration of the KIO3,mL.9.3 Fill the funnel-topped 50-mL b
26、uret with the 0.1 N iodinesolution to be standardized. Measure approximately 40 mL ofthe iodine solution into a 250-mL Erlenmeyer flask, and readthe buret to the nearest 0.1 mL. Add approximately 50 mL ofwater to the flask containing the iodine solution, and titratewith the standardized 0.1 N Na2S2O
27、3solution as described in9.1.9.4 Calculate the normality N1of the iodine solution asfollows:N15 V 3 N!/V1(1)where:V = volume of Na2S2O3required for titration of the iodinesolution, mL,N = normality of the Na2S2O3solution, andV1= volume of iodine solution used for standardization,mL.10. Procedure10.1
28、 Pipet 50 mL of Na2S2O5solution (7.5) into each of twoglass-stoppered 500-mL Erlenmeyer flasks.Add approximately25 g of clean chipped ice to each flask and into one of the flaskspipet 100 mL of the sample. Grease the stoppers and place theflasks on a mechanical shaker, allowing them to shake for 10
29、61 min.10.2 At the end of the 10-min reaction period, add 0.5 mLof starch indicator to the blank and specimen. Titrate the excesssodium bisulfite with the standard iodine solution. The endpoint is when the first permanent blue color is obtained.NOTE 2In order to maintain good drainage of the iodine
30、solution, careshould be taken to always use a clean buret which should be filled with theiodine solution just before beginning each series of titrations.11. Calculation11.1 Calculate the weight percent aldehyde content of thevinyl acetate, as acetaldehyde, A, as follows:A 5 B 2 V2! 3 N130.02202!/D 3
31、 M!# 3100 (2)where:B = volume of iodine required for the titration of the blank,mL,V2= volume of iodine required for titration of the specimen,mL,N1= normality of the iodine solution,D = specific gravity of the sample, andM = volume of sample used, mL.12. Report12.1 Report the following information:
32、 weight percent ac-etaldehyde to the nearest 0.001 %. Duplicate runs that agreewithin 0.003 % are acceptable for averaging (95 % confidencelevel).13. Precision and Bias13.1 PrecisionThe following criteria should be used forjudging the acceptability of results at the 95 % confidencelevel:D2191 06 (20
33、12)213.1.1 RepeatabilityTwo results, each the mean of dupli-cate determinations, obtained by the same analyst should beconsidered suspect if they differ by more than 0.006 %absolute.13.1.2 ReproducibilityTwo results, each the mean of du-plicate determinations, obtained by analysts in different labo-
34、ratories should be considered suspect if they differ by morethan 0.008 % absolute.NOTE 3The above precision estimates are based upon an interlabo-ratory study on four samples of vinyl acetate containing 0.01, 0.02, 0.03,and 0.05 % acetaldehyde. Two analysts in each of three different labora-tories p
35、erformed duplicate determinations on each sample on two succes-sive days making a total of 96 determinations.13.2 BiasBias has not been determined for this testmethod because there is no appropriate standard available.14. Keywords14.1 acetaldehyde ; vinyl acetateSUMMARY OF CHANGESCommittee D01.35 ha
36、s identified the location of selected changes to this standard since the last issue(D2191 97 (2001) that may impact the use of this standard. (Approved April 1, 2006.)(1) Added reference to Practice E29 in the scope section. (2) Added Practice E29 to list of Referenced Documents.ASTM International t
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39、essed 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 on Standards, at
40、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 ASTM website (www.astm.org/COPYRIGHT/).D2191 06 (2012)3
