1、Designation: E 298 01Standard Test Methods forAssay of Organic Peroxides1This standard is issued under the fixed designation E 298; 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 parentheses
2、indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 These test methods cover the assay of organic peroxides.Two procedures are given, depending upon the ease of reduc-tion:1.1.1 Sodium Iodide, Room Temperatur
3、e Test Method, fororganic peroxides easy to reduce, and1.1.2 Sodium Iodide, 60C Test Method, for organic perox-ides that are moderately stable.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standar
4、d to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.3 Review the current material safety data sheets (MSDS)for detailed information concerning toxicity, first-aid proce-dures, and safety precautions.2. Referenced Documents
5、2.1 ASTM Standards:D 1193 Specification for Reagent Water2E 180 Practice for Determining the Precision of ASTMMethods for Analysis and Testing of Industrial Chemicals3E 200 Practice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis33. Significance
6、and Use3.1 Organic peroxides are widely used as chemical interme-diates, catalysts, and initiators. These test methods provideprocedures for assaying organic peroxides to determine if theyare suitable for their intended use.4. Purity of Reagents4.1 Purity of ReagentsReagent grade chemicals shall beu
7、sed 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 that the reag
8、ent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.4.2 Unless otherwise indicated, references to water shall beunderstood to mean Type II or Type III reagent water conform-ing to Specification D 1193.SODIUM IODIDE, ROOM TEMPERATURE TESTMETHOD5. Sco
9、pe5.1 This test method covers the assay of organic peroxidesthat are easily reduced, such as hydroperoxides and diacylperoxides. Dialkyl peroxides do not react, while peresters andbridge-type peroxides like ascaridole react slowly and incom-pletely.5.2 Specific peroxides that can be analyzed by this
10、 proce-dure include the following:5.2.1 Diacyl PeroxidesBenzoyl 2,4-dichlorobenzoyl,p-chlorobenzoyl, lauroyl, acetyl, and decanoyl peroxides.5.2.2 Dibasic Acid PeroxideSuccinic acid peroxide.5.2.3 Ketone PeroxidesCyclohexanone peroxide and me-thyl ethyl ketone peroxide.5.2.4 Alkyl Hydroperoxidestert
11、-Butylhydroperoxide and2,5-dimethylhexane-2,5-dihydroperoxide.6. Summary of Test Method6.1 A sample is dissolved in a mixture of methylenechloride and acetic acid. A saturated solution of sodium iodideis added and the mixture is allowed to react in the dark at roomtemperature for 15 min. The liberat
12、ed iodine is then titratedwith standard sodium thiosulfate solution.7. Interferences7.1 Conjugated diolefins interfere by absorbing iodine.8. Apparatus8.1 Iodine Flasks, 250-mL, with stoppers.NOTE 1All glassware should be thoroughly cleaned before use.1These test methods are under the jurisdiction o
13、f ASTM Committee E15 onIndustrial and Specialty Chemicalsand are the direct responsibility of SubcommitteeE15.01 on General Standards.Current edition approved Oct. 10, 2001. Published December 2001. Originallypublished as E 298 66 T. Last previous edition E 298 98.2Annual Book of ASTM Standards, Vol
14、 11.01.3Annual Book of ASTM Standards, Vol 15.05.4Reagent 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., Pool
15、e, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.9. Reagents9.1 Acetic Acid, Glacial.9.2 Carbon Dioxide, cylinder.9.3 Methylene C
16、hloride.9.4 Sodium Iodide, Saturated SolutionPrepare a saturatedsolution of sodium iodide (NaI) in de-aerated water. Thissolution should be prepared just prior to use and kept in abrown bottle.9.5 Sodium Thiosulfate, Standard Solution (0.1 N)Prepareand standardize a 0.1 N solution of sodium thiosulf
17、ate(Na2S2O3) in accordance with the appropriate sections ofPractice E 200.9.6 Starch Indicator Solution (10 g/L), Prepare as describedin the appropriate sections of Practice E 200.9.7 Water, De-aeratedPass carbon dioxide (CO2) throughdistilled water for several minutes prior to use.10. Procedure10.1
18、 Add 20 mL of acetic acid to a 250-mL iodine flask andsparge with a rapid flow of CO2for 2 min. Stopper the flaskand reserve for the sample.10.2 Accurately weigh a sample containing 3 to 4 meq ofactive oxygen to the nearest 0.1 mg and transfer to the flask.Volatile liquid peroxides may be diluted to
19、 a known volumewith acetic acid and aliquots taken for analysis.NOTE 2The approximate weight of the sample to be used in theanalysis may be calculated as follows:Sample weight, g 5 3.5M/2C 3 1000 (1)where:M = molecular weight of the compound, andC = number of peroxide groups in the molecule.10.3 Add
20、 10 mL of methylene chloride and restopper. Swirlbriefly to dissolve the sample.10.4 Add 5 mL of freshly prepared saturated NaI solution.Restopper and swirl. Place a few millilitres of water in the wellof the flask and allow to stand in the dark at room temperaturefor 15 min.10.5 Add 50 mL of de-aer
21、ated water and titrate with 0.1 NNa2S2O3solution until the solution is a pale straw color. Add1 to 2 mL of starch solution and continue the titration to thesharp disappearance of the blue color. Record the number ofmillilitres required for titration.10.6 Subtract the number of millilitres required f
22、or titrationof a blank carried through the entire procedure and calculatethe assay value of the sample.NOTE 3The blank titration should normally require 0.05 mL or less of0.1 N Na2S2O3solution. The results should be discarded and the analysisrepeated if high blank values are obtained.11. Calculation
23、11.1 Calculate the assay as follows:Assay, as percent compound 5 A 2 B! 3 N 3 M 3 100/W 3 2C3 1000 (2)where:A =mLofNa2S2O3solution required for titration of thesample,B =mLofNa2S2O3solution required for titration of theblank,N = normality of the Na2S2O3solution,C = number of peroxide groups in the m
24、olecule,M = molecular weight of the compound, andW = grams of sample used.11.2 Calculate the percent active oxygen in the compoundas follows:Active oxygen, % 5 A 2 B! 3 N 3 0.0083 100/W (3)11.3 If required, the percent active oxygen can be con-verted to a specific peroxide using the appropriate conv
25、ersionfactor.Peroxide X,%5 % Active Oxygen in Peroxide X 3 F (4)where:F = conversion factor for Compound X.11.3.1 Conversion Factors for some common peroxides areas follows:Cumene Hydroperoxide = 9.5125Benzoyl Peroxide = 15.140t-Butyl Hydroperoxide = 5.6328Lauroyl Peroxide = 24.91512. Report12.1 Rep
26、ort the assay value of the compound to the nearest0.01%.13. Precision and Bias513.1 The following criteria shall be used for judging theacceptability of results (Note 4):13.1.1 Repeatability (Single Analyst)The standard devia-tion for a single determination has been estimated to be0.047 % absolute a
27、t 36 df. The 95 % limit for the differencebetween two such determinations is 0.13 % absolute.13.1.2 Laboratory Precision (Within-Laboratory, Between-Days Variability, Formerly Called Repeatability)The stan-dard deviation of results (each the average of duplicates)obtained by the same analyst on diff
28、erent days, has beenestimated to be 0.010 % absolute at 18 df. The 95 % limit forthe difference between two such averages is 0.028 % absolute.13.1.3 Reproducibility (Multilaboratory)The standard de-viation of results (each the average of duplicates) obtained byanalysts in different laboratories has
29、been estimated to be0.035 % absolute at 5 df. The 95 % limit for the differencebetween two such averages is 0.10 % absolute.NOTE 4These precision estimates are based on an interlaboratorystudy in which 3 samples were analyzed. One analyst in each of 6laboratories performed duplicate determinations a
30、nd repeated them on asecond day, for a total of 72 determinations. Practice E 180 was used indeveloping these statements.13.2 BiasThe bias of this test method has not beendetermined due to the lack of suitable reference materials ormethodology.SODIUM IODIDE, 60C TEST METHOD14. Scope14.1 This test me
31、thod covers the assay of organic peroxides5Supporting data are available from ASTM Headquarters. Request RR: E15-1001.E 2982that are moderately stable, such as peresters, di-acyl peroxides,and n-alkyl peroxides. These peroxides react slowly withsodium iodide at room temperature, but do not require t
32、he useof hydroiodic acid.14.2 Specific peroxides that can be analyzed by this proce-dure include the following: t-butyl peracetate, t-butyl peroxy-isobutyrate, di-t-butyl diperphthalate, t-butyl perbenzoate, and2,2-bis(t-butylperoxy) butane.15. Summary of Test Method15.1 A sample is dissolved in gla
33、cial acetic acid. Saturatedsodium iodide solution is then added and the mixture isallowed to react for1hat60C. The liberated iodine is titratedwith standard sodium thiosulfate solution.16. Interferences16.1 Conjugated diolefins interfere under the conditions ofanalysis by absorbing iodine.17. Appara
34、tus17.1 Iodine Flasks, 250-mL with stopper (Note 1).17.2 Water Bath, maintained at 60 6 1C.18. Reagents18.1 Acetic Acid, Glacial.18.2 Carbon Dioxide, cylinder.18.3 Sodium Iodide, Saturated SolutionSee 9.4.18.4 Sodium Thiosulfate, Standard Solution (0.1 N)See9.5.18.5 Starch Indicator SolutionSee 9.6.
35、18.6 Water, De-aeratedSee 9.7.19. Procedure19.1 Add 20 mL of acetic acid to a 250-mL iodine flask andsparge with a rapid flow of carbon dioxide (CO2) for 2 min.Stopper the flask and reserve for the sample.19.2 Accurately weigh a sample containing 3 to 4 meq ofactive oxygen to the nearest 0.1 mg and
36、transfer to the flask(Note 2).19.3 Add 5 mL of freshly prepared saturated NaI solution(Note 5). Restopper tightly and swirl. Place a few millilitres ofwater in the well of the flask and allow the flask to standpartially submerged in a water bath maintained at 60C for 1 h.NOTE 5Some peroxides may req
37、uire the addition of a small amountof hydrochloric acid (HCl) to react completely in a reasonable time. In thiscase 1 mL of concentrated HCl shall be added to the solution just beforeit is placed in the water bath.19.4 Remove the flask from the bath and cool to roomtemperature.19.5 Add 60 mL of de-a
38、erated water and titrate with 0.1 NNa2S2O3solution until the solution is a pale straw color. Add1 to 2 mL of starch solution and continue the titration to thesharp disappearance of the blue color. Record the number ofmillilitres required for titration.19.6 Subtract the number of millilitres required
39、 for titrationof a blank carried through the entire procedure and calculatethe assay value of the sample.NOTE 6The blank titration should normally require about 0.10 mL of0.1 N Na2S2O3solution. The results should be discarded and the analysisrepeated if high blank values are obtained.20. Calculation
40、20.1 Calculate the assay as follows:Assay, as percent compound5 A 2 B! 3 N 3 M 3 100/W 3 2C3 1000 (5)where:A =mLofNa2S2O3solution required for titration of thesample,B =mLofNa2S2O3solution required for titration of theblank,N = normality of the Na2S2O3solution,C = number of peroxide groups in the mo
41、lecule,M = molecular weight of the compound, andW = grams of sample used.20.2 Calculate the percent of active oxygen in the com-pound as follows:Active oxygen, % 5 A 2 B! 3 N 3 0.008/W 3 100 (6)20.3 If required, the percent active oxygen can be convertedto a specific peroxide using the appropriate c
42、onversion factor.See 11.3.21. Report21.1 Report the assay value of the compound to the nearest0.01 %.22. Precision and Bias522.1 The following criteria should be used in judging theacceptability of results (Note 7):22.1.1 Repeatability (Single Analyst)The standard devia-tion for a single determinati
43、on has been estimated to be0.080 % absolute at 24 df. The 95 % limit for the differencebetween two such determinations is 0.23 % absolute.22.1.2 Laboratory Precision (Within-Laboratory, Between-Days Variability, Formerly called Repeatability)The stan-dard deviation of results (each the average of du
44、plicates)obtained by the same analyst on different days, has beenestimated to be 0.055 % absolute at 12 df. The 95 % limit forthe difference between two such averages is 0.15 % absolute.22.1.3 Reproducibility (Multilaboratory)The standard de-viation of results (each the average of duplicates) obtain
45、ed byanalysts in different laboratories has been estimated to be0.126 % absolute at 5 df. The 95 % limit for the differencebetween two such averages is 0.35 % absolute.NOTE 7These precision estimates are based on an interlaboratorystudy conducted in which 2 samples were analyzed. One analyst in each
46、of 6 laboratories performed duplicate determinations and repeated them ona second day, for a total of 48 determinations. Practice E 180 was used indeveloping these statements.22.2 BiasThe bias of this test method has not beendetermined due to the lack of suitable reference materials ormethodology.23
47、. Keywords23.1 assay; iodometric; organic peroxide; peroxidesE 2983The ASTM International takes no position respecting the validity of any patent rights asserted in connection with any itemmentioned in this standard. Users of this standard are expressly advised that determination of the validity of
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