1、Designation: D7637 10Standard Test Method forDetermination of Glycerin Assay by Titration (Sodium MetaPeriodate)1This standard is issued under the fixed designation D7637; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、 last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method provides the quantitative determinationof glycerin by the titrimetric method. It is applicable to al
3、lglycerin or glycerin/water mixtures 75 %.1.2 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.3 This standard may involve hazardous materials, opera-tions and equipment. This standard does not purport to addressall of the safe
4、ty problems associated with its use. It is theresponsibility of whoever uses this standard to consult theestablished and appropriate safety and health practices anddetermine the applicability of regulatory limitations prior touse. Specific precautions are listed in Section 8.2. Referenced Documents2
5、.1 ASTM Standards:2D1193 Specification for Reagent WaterD4725 Terminology for Engine CoolantsE177 Practice for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other Standards:The United States
6、Pharmacopoeia 31 Glycerin Monograph Assay Method3AOCS Official Method EA6-94 (ReplacesAOCS EA6-51),Determination of Crude Glycerin, Titrimetric Method4BS 5711: Part 3, 1979 Sampling and Test for Glycerol -Determination of Glycerol Content53. Terminology3.1 Definitions:3.1.1 glycerinpropane-1,2,3-tri
7、ol, C3H5(OH)3(alsoknown as glycerine), 1,2,3-propanetriol, 1,2,3-trihydroxypropane, glyceritol, glycyl alcohol, glycerol. CAS#56-81-5.3.1.2 SMPSodium Meta Periodate.3.1.3 For other definitions of terms used in this specifica-tion, refer to Terminology D4725.4. Significance and Use4.1 This test metho
8、d is based on the cold oxidation of theglycerol by sodium metaperiodate in a strong acidic medium.Formaldehyde and formic acid are produced in this reactionand the latter is used to measure the glycerol content bytitration with standard sodium hydroxide solution, to a pH 8.16 0.1. The glycerol conte
9、nt is expressed as a percentage(m/m).CH2OH 2 CHOH 2 CH2OH 1 2 NaIO4HCOOH 1 2 HCHO 1 2 NaIO31 H2O (1)4.2 InterferencesThe glycerin sample should be free oforganic compounds with more than two hydroxyl groups onadjacent carbon atoms (for example, sugars, glycols). Thesetypes of compounds may produce f
10、ormic acid which interfereswith the determination of the glycerol content.5. Apparatus5.1 Burette50 mL “Type A” unit that can deliver 30 dropsper mL and calibrated to meet the NIST standards.NOTE 1 It is critical that all glassware be “Type A” and thoroughlycleaned before use as dirty glassware will
11、 impact the analysis results.5.2 pH meter, fitted with glass electrode.NOTE 2The pH meter should be standardized with a minimum of twobuffer solutions at 10.0 and 7.0. (See 7.12.)5.3 Stirrerpreference should be given to a magneticstirrer. In this case, check that it does not influence the pHmeter.1T
12、his test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and is the direct responsibility of Subcommittee D15.93 on Research andLong Range Planning.Current edition approved June 1, 2010. Published July 2010. DOI: 10.1520/D763710.2For referenced ASTM standards, visit the ASTM
13、 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.3Available from U.S. Pharmacopeia (USP), 12601 Twinbrook Pkwy., Rockville,MD 20852-1790, http:/www.usp.org.
14、4Available from AOCS, 2710 S. Boulder, Urbana, IL 61802-6996, http:/www.aocs.org.5Available from British Standards Institute (BSI), 389 Chiswick High Rd.,London W4 4AL, U.K., http:/www.bsi-.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United St
15、ates.6. Purity of Reagents and Water6.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are
16、available. Other grades may be usedprovided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.6.2 Purity of WaterUnless indicated otherwise, referencesto water shall be understood to mean Type II reagent water
17、asdefined in Specification D1193.NOTE 3The presence of carbon dioxide can introduce errors; there-fore it is advisable to prepare 500 mL of water by boiling for 5 min andcooling to room temperature. Check the pH of the distilled water beforeuse. The pH should be 7.0 6 0.1. If not, adjust the pH with
18、 0.1 N sodiumhydroxide (NaOH) or 0.1 N hydrogen chloride (HCl), whichever isappropriate. Store the freshly boiled and neutralized water in a tightlyclosed container.7. Reagents7.1 Sodium Metaperiodate, NaIO4, acidic solutionDissolve 60 g of sodium metaperiodate in sufficient watercontaining 120 mL o
19、f 0.1 N sulfuric acid to make 1000 mL. Donot heat to dissolve the periodate. If the solution is not clear,pass it through a sintered-glass filter. Store the solution in aglass-stoppered, light-resistant container.7.2 Hydrochloric Acid, aqueous solution, approximately 0.1N.7.3 Sodium Hydroxide, aqueo
20、us solution, approximately0.05 N.7.4 Sodium Hydroxide, 0.1 N, Standardized Dissolve fourgrams of sodium hydroxide (NaOH) in water and dilute to oneliter. Standardize accurately to 60.0001 N. The standardizedsodium hydroxide solution should be protected against evapo-ration and absorption of carbon d
21、ioxide (CO2) from the air.7.5 Ethylene glycol (1,2-ethanediol, free from glycerol)solution in water. 1:1 (v/v).7.6 SulfuricAcid Solution, aqueous solution, approximately0.1 N.7.7 SulfuricAcid Solution, aqueous solution, approximately0.2 N.7.8 Sodium Thiosulfate, 0.1 N, aqueous solution.7.9 Potassium
22、 Iodide, aqueous solutionDissolve 16.5 g ofpotassium iodide in water to make 100 mL. Store tightlycapped in a light-resistant container.7.10 Starch SolutionMix 1g of soluble starch with suffi-cient cold water to make a thin paste. Add 200 mL of boilingwater, and boil for 1 min with continuous stirri
23、ng. Cool, anduse only the clear solution.NOTE 4It is recommended that freshly prepared starch solution beused to ensure a sharper endpoint. Commercially available, stabilizedstarch indicator solution may be also used in place of freshly preparedstarch.7.11 Bromothymol blue indicator solutionDissolve
24、 100mg of bromothymol blue in 100 mL of water to make 100 mLof indicator solution.7.12 pH Buffers (7.0 6 0.01 and 10.0 6 0.01 at 25C)needed for pH meter standardization.7.13 Freshly boiled water, or equivalent. (See 6.2.)8. Precautions8.1 Sulfuric acid and sodium hydroxide solutions are cor-rosive.
25、Avoid eye and skin contact.8.2 Please study and be aware of the Material Safety DataSheet and correct laboratory performance for the appropriatehealth and safety precautions that may apply to any of thechemicals and equipment prior to use.8.3 It is the responsibility of each organization to conduct
26、ajob hazard analysis to assess safety risks and PPE needed forperformance of this test method.9. Procedure9.1 Sodium Periodate Solution Suitability TestPipet 10mL of the prepared sodium periodate solution (Reagent 7.1)into a 250-mL volumetric flask, dilute with water to volume,and mix.9.2 Weigh appr
27、oximately 550 mg of glycerin into flask.Dissolve the sample in 50 mLof water and pipette 50 mLof thediluted periodate solution prepared in 9.1.Allow the solution tostand for 30 min.9.3 Add 5 mL of hydrochloric acid solution (Reagent 7.2)and 10 mL of potassium iodide solution (Reagent 7.9), andgently
28、 swirl to mix. Allow the solution to stand for 5 min.9.4 Add 100 mL of water and 3 mL of starch solution(Reagent 7.10). Titrate slowly with 0.1 N sodium thiosulfate(Reagent 7.8) to the starch endpoint, mixing continuously toensure the solution has stabilized after each addition.9.5 Blank Test for So
29、dium Periodate Solution SuitabilityTestFor the blank, pipet 50 mL of the diluted periodatesolution into a flask containing 50 mL of water. Carry out, atthe same time as the determination and under the sameconditions, a blank test without the glycerin test portion usingthe same quantities of reagents
30、 and diluting water for thedeterminations as outlined in 9.1 through 9.4.9.6 The ratio of the volume of 0.1 N sodium thiosulfate(Reagent 7.8) required for the glycerin-periodate mixture tothat required for the blank should be between 0.750 and 0.765.9.7 Glycerol Assay DeterminationTransfer about 400
31、 mgof glycerin, accurately weighed on an analytical balance, intoa 600 mL beaker.9.8 Dilute the sample in the beaker with 50 mL of water andadd approximately 3 mL of bromothymol blue indicator(Reagent 7.11). Carefully acidify with 0.2 N sulfuric acid(Reagent 7.7) to a definite green or greenish yell
32、ow color.Neutralize with 0.05 N sodium hydroxide (Reagent 7.3)toadefinite blue endpoint, free from green color.9.9 Pipette 50 mL of sodium metaperiodate solution (Re-agent 7.1) into the beaker. Mix using moderate agitation andcover the beaker with a watch glass. Allow the beaker to standfor 30 min a
33、t room temperature (not exceeding 35C) in thedark or in subdued light.NOTE 5The presence of carbon dioxide can introduce errors; there-fore it is advisable to cover the beaker containing the test solution with awatch glass during all standing periods.D7637 1029.10 Add 10 mL of the ethylene glycol so
34、lution (Reagent7.5) into the beaker. Mix using moderate agitation and coverthe beaker with a watch glass. Allow the beaker to stand for 20min at room temperature (not exceeding 35C) in the dark or insubdued light.9.11 Dilute the solution with water to about 300 mL.9.12 Insert the glass electrode and
35、 using moderate stirring,titrate slowly as the endpoint is approached with 0.1 N sodiumhydroxide (Reagent 7.4)toapHof8.16 0.1 for the specimenunder assay.NOTE 6When approaching the endpoint, it is critical that the titrationis conducted slowly and the solution is well mixed after each addition toens
36、ure a stable pH reading for the endpoint determination.9.13 Blank Determination for Glycerine AssayDeterminationCarry out, at the same time as the assaydetermination and under the same conditions, a blank testwithout the test portion using the same quantities of reagentsand diluting water for the de
37、terminations as outlined in 9.5through 9.12. Titrate with 0.1 N sodium hydroxide to a pH of6.5 6 0.1 for the blank.9.14 Each mL of 0.1 N sodium hydroxide, after correctionfor the blank, is equivalent to 9.210 mg of glycerol (C3H8O3).10. Calculation10.1 The glycerol content, expressed as a percentage
38、, isgiven by the formula:Glycerol %! 5V1VB! 3 F 3 NW(2)where:V1= number of mL of 0.1 N sodium hydroxide solutionused for the sample titration,VB= number of mL of 0.1 N sodium hydroxide solutionused for the blank titration,F = Factor = 9.210,N = exact normality of sodium hydroxide that was usedfor th
39、e titration, andW = mass, in g, of glycerin subjected to the reaction withsodium metaperiodate solution.11. Report11.1 Report the glycerin content of the sample to the nearest0.1 %.12. Precision and Bias12.1 The precision of this test method is based on aninterlaboratory study conducted in 2009. Eac
40、h of eight labora-tories tested two different materials. Every “test result” repre-sents an individual determination, and every laboratory re-ported two replicate test results for each of the materials.Except for the use of only two test materials, Practice E691was followed for the design and analys
41、is of the data; the detailsare given in an ASTM Research Report.612.1.1 Repeatability Limit (r)Two test results obtainedwithin one laboratory shall be judged not equivalent if theydiffer by more than the “r” value for that material; “r”istheinterval representing the critical difference between two t
42、estresults for the same material, obtained by the same operatorusing the same equipment on the same day in the samelaboratory.12.1.1.1 Repeatability limits are listed in Table 1.12.1.2 Reproducibility Limit (R)Two test results shall bejudged not equivalent if they differ by more than the “R” valuefo
43、r that material; “R” is the interval representing the criticaldifference between two test results for the same material,obtained by different operators using different equipment indifferent laboratories.12.1.2.1 Reproducibility limits are listed in Table 1.12.1.3 The terms (repeatability limit and r
44、eproducibilitylimit) are used as specified in Practice E177.12.1.4 Any judgment in accordance with statements 12.1.1and 12.1.2 would have an approximate 95 % probability ofbeing correct.12.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for t
45、his testmethod, therefore no statement on bias is being made.12.3 The precision statement was determined through sta-tistical examination of 26 results, from eight laboratories, ontwo materials. These two materials were described as thefollowing:Glycerin A: a 99.5 % pure glycerine (data fromseven la
46、boratories included)Glycerin B: a 97.5 % solution of glycerine (datafrom six laboratories included)12.4 To judge the equivalency of two test results, it isrecommended to choose the type of glycerin closest in char-acteristics to the test fluid.13. Keywords13.1 antifreeze; engine coolant; ethylene; g
47、lycerin; glycer-ine; glycerol; titrimetric6Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D15-1025.TABLE 1 Glycerin (%)Material AverageARepeatabilityStandardDeviationReproducibilityStandardDeviationRepeatabilityLimitReproducibil
48、ityLimitxSxSrSRrRA 99.48 0.14 0.29 0.29 0.81 0.81B 97.48 0.36 0.17 0.38 0.48 1.05AThe average of the laboratories calculated averages.D7637 103ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of th
49、is 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 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 either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful c
