1、Designation: D 2191 06Standard Test Method forAcetaldehyde Content of Vinyl Acetate1This standard is issued under the fixed designation D 2191; 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
2、parentheses 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 tracequantities of acetaldehyde, in the range from 0.00 to 0.05 %,contained in 99 % grade vinyl ac
3、etate.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 the rounding-o
4、ff methodof Practice E 29.1.3 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 of thesafety co
5、ncerns, 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 Documents2.1 ASTM Sta
6、ndards:2D 1193 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 bisulfite co
7、nsumed, 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 be used for s
8、pecification 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-stoppered.6.
9、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 available.3Othergr
10、ades 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 definedby Type IV
11、of Specification D 1193.7.3 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 thiosulfate (Na2S2O3)
12、solution. (See standardizationprocedure, 9.3 and 9.4.)7.4 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.1This test method is under the j
13、urisdiction 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.Current edition approved April 1, 2006. Published April 2006. Originallyapproved in 1963. Last prev
14、ious edition approved in 2001 as D 2191 97 (2001).2For 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.3Reagent Ch
15、emicals, 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 Pharmacopeiaand Natio
16、nal 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.7.6 Sodium Thiosulfate, Standard Solution (0.1
17、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 weekly, as required, again
18、st potassiumiodate (KIO3). (See standardization procedure, 9.1 and 9.2.)7.7 Starch IndicatorMake a paste of6gofpowderedsoluble starch in water, and dilute to 1 L with water, stirring toproduce a suspension. While stirring, add 20 g of potassiumhydroxide (KOH) pellets, and continue stirring until the
19、 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 800mL of water in a 1-L volum
20、etric 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; use specialprecautions when h
21、andling 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 a desiccator until cool. Wei
22、gh 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 standardized and titrate the
23、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 thiosulfate, thestarch indicator
24、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 isformed, that would give err
25、oneous results.9.2 Calculate the normality N of the Na2S2O3solution asfollows:N 5 W 3 P!/V 3 0.035669!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 buret with the 0.1 N iodineso
26、lution 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 Na2S2O3solution as described in9.1
27、.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 Pipet 50 mL of Na2S2O5solut
28、ion (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 61 min.10.2 At the end of th
29、e 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 solution, careshould be take
30、n 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 N13 0.02202!/D 3 M!# 3 100 (2)where:B = vol
31、ume of iodine required for the titration of theblank, mL,V2= volume of iodine required for titration of the speci-men, 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: weight percent ac-etald
32、ehyde 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:13.1.1 RepeatabilityTwo results, eac
33、h the mean of dupli-cate determinations, obtained by the same analyst should beconsidered suspect if they differ by more than 0.006 %absolute.D219106213.1.2 ReproducibilityTwo results, each the mean of du-plicate determinations, obtained by analysts in different labo-ratories should be considered su
34、spect 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 performed duplicate determination
35、s 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 has identified the location of sele
36、cted changes to this standard since the last issue(D 2191 97 (2001) that may impact the use of this standard. (Approved April 1, 2006.)(1) Added reference to Practice E29in the scope section. (2) Added Practice E29to list of Referenced Documents.ASTM International takes no position respecting the va
37、lidity 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 entirely their own responsibility.This standard is su
38、bject 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 standardsand should be addressed to ASTM International Headqu
39、arters. 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 the address shown below.This stand
40、ard 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).D2191063
