1、Designation: D7736 12 (Reapproved 2018)Standard Test Method forDetermination of Acids and Glycol Esters in EthyleneGlycol1This standard is issued under the fixed designation D7736; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th
2、e year of 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 covers the determination of free acidsand glycol esters in ethylene glycol by titration.1.2
3、 This test method is for used on ethylene glycol used forthe manufacture of engine coolant. It can not be used onformulated engine coolant. The inhibitors will interfere withthe determination.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included
4、in thisstandard.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 of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitati
5、ons prior to use.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization Tec
6、hnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1176 Practice for Sampling and Preparing Aqueous Solu-tions of Engine Coolants or Antirusts for Testing PurposesD1193 Specification for Reagent WaterD4725 Terminology for Engine Coolants and Related FluidsE177 Practi
7、ce for Use of the Terms Precision and Bias inASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, referto Terminology D4725.4. Summary of Test Method4.1
8、This test method is used to determine the acid and estercontent of ethylene glycol by titration. The sample is titrated tothe phenolphthalein end point with 0.02 N NaOH to determinethe acidity. Then a known amount of base is added and thesample is heated at 100 C to hydrolyze the esters. It is thenb
9、ack-titrated with 0.02 N sulfuric acid to determine the estercontent.5. Significance and Use5.1 The presence of acids or glycol esters in the ethyleneglycol used to produce engine coolant is undesirable. Underconditions in an engine cooling system, the esters can hydro-lyze to form glycol and an aci
10、d. The acid will react with thecorrosion inhibitors, thereby reducing the useful life of thecoolant. This method can determine the amount of acid andglycol ester present in the ethylene glycol.6. Interferences6.1 This test method is based on a color change titration.Glycol with a strong color could
11、interfere with the results ofthis method.6.2 High pH recycled glycols streams will affect the resultsof this test method.7. Apparatus7.1 250 mL Borosilicate Glass Bottles, with screw caps.8. Reagents and Materials8.1 Phenolphthalein SolutionDissolve 0.5 g of phenol-phthalein in methanol or ethanol a
12、nd dilute to 100 mL.8.2 Sodium Hydroxide (NaOH), 0.02 N in water.8.3 Sulfuric Acid (H2SO4), 0.02 N in water.1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and Related Fluids and is the direct responsibility of SubcommitteeD15.04 on Chemical Properties.Current edi
13、tion approved March 1, 2018. Published March 2018. Originallyapproved in 2011. Last previous edition approved in 2012 as D7736 - 12. DOI:10.1520/D7736-12R18.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of AS
14、TMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized pri
15、nciples on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.18.4 Purity of WaterUnless otherwise indicated, referencesto water shall b
16、e understood to mean reagent water as definedby Type II or III of Specification D1193.8.5 Purity of ReagentsReagent grade chemicals 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 t
17、he American Chemical Society,where such specifications are available.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.9. Sampling9.1 Sample the material in accordance with Pr
18、actice D1176.10. Procedure10.1 Acid Content:10.1.1 Adjustment of pHPipet 25.00 mL of deionizedwater into each of three 250 mL bottles. Add 3 drops ofphenolphthalein solution to each. Titrate with 0.02 N sodiumhydroxide to the first pink end point permanent for at least 15 s.Do not record this volume
19、 of titrant. Repeat for each bottle.10.1.2 Determination of Sample Acidity:10.1.2.1 Add an amount of sample as indicated in Table 1 tothe nearest 0.1 g into the bottle of deionized water prepared in10.1.1.10.1.2.2 Titrate each sample with 0.02 N sodium hydroxideto the first pink end point permanent
20、for at least 15 s. Thisvolume of titrant is used to calculate the percent acid.NOTE 1If the ester content is completely unknown, a trial titrationbeginning with 25 g of sample may be conducted to develop a preliminaryestimate before the actual test titration is performed. If the trial suggestsconcen
21、tration of over 0.10 wt % (1000 ppm) then reduce the sample to 10g and repeat. The second trial should provide enough information to directan appropriate choice of the sample quantity to be used.10.2 Total Ester Content:10.2.1 Hydrolysis of the EstersPipet 25.00 mL of 0.02 Nsodium hydroxide into eac
22、h bottle used in 10.1.2. Prepare ablank for each sample by pipetting 25.00 mL of 0.02 N sodiumhydroxide into three clean, 250 mL bottles. Immerse the pairsof bottles in a boiling water bath for 1 h. (Tap water is suitable.)The weight of the bottles should prevent tipping. Leave capsslightly loose to
23、 prevent pressure buildup.10.2.2 Determination of the Ester ContentRemove bottlesfrom the bath and cool to room temperature. When cool, add 3drops of phenolphthalein solution to each and titrate with 0.02NH2SO4until disappearance of pink color.11. Calculation11.1 Acidity:% acetic acid5mL NaOH!N NaOH
24、!60.0 g/equivalent!1 L/1000 mL!g of sample3100where:N = normality of the NaOH used.11.2 Ester Content:% esters as acetic acid!5B 2 A!NH2SO4!60.0g/equivalent!1 L/1000 mL!g of sample3100esters, ppm as acetic acid! 5 % esters as acetic acid! 310 000where:N = normality of the H2SO4used,B =H2SO4used to t
25、itrate the blank, mL, andA =H2SO4used to titrate the sample, mL.12. Report12.1 Report the average of the three determinations ofacidity as mass percent acetic acid.12.2 Report the average of the three determinations of theester content as ppm acetic acid.13. Precision and Bias413.1 The precision of
26、this test method is based on aninterlaboratory study conducted in 2009. Each of four labora-tories tested four different materials. Every “test result” repre-sents an individual determination. All laboratories were askedto report duplicate test results from a single operator for everymaterial. Excep
27、t for the limited number of laboratoriesinvolved, and the inability of all participants to report allrequested replicates, Practice E691 was followed for the designand analysis of the data; the details are given in RR:D15-1031.13.1.1 Repeatability Limit, rTwo test results obtainedwithin one laborato
28、ry shall be judged not equivalent if theydiffer by more than the r value for that material; r is the intervalrepresenting the critical difference between two test results forthe same material, obtained by the same operator using thesame equipment on the same day in the same laboratory.13.1.1.1 Repea
29、tability limits are listed in Table 2.13.1.2 Reproducibility Limit, RTwo test results shall bejudged not equivalent if they differ by more than the R valuefor that material; R is the interval representing the criticaldifference between two test results for the same material,obtained by different ope
30、rators using different equipment indifferent laboratories.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH L
31、td., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D15-1031.TABLE 1 Recommended Sample Siz
32、esEstimated EsterContent, wt %Sample Size, g Sample Method0.50 wt %” if the titration determination exceeds 0.50 %.D7736 12 (2018)213.1.2.1 Reproducibility limits are listed in Table 2.13.1.3 The above terms (repeatability limit and reproduc-ibility limit) are used as specified in Practice E177.13.1
33、.4 Any judgment in accordance with statements 13.1.1and 13.1.2 would normally have an approximate 95 % prob-ability of being correct, however the precision statistics ob-tained in this interlaboratory study (ILS) shall not be treated asexact mathematical quantities that are applicable to all circum-
34、stances and uses. The limited number of materials tested andlaboratories reporting replicate results guarantees that therewill be times when differences greater than predicted by theILS results will arise, sometimes with considerably greater orsmaller frequency than the 95 % probability limit would
35、imply.Consider the repeatability limit and the reproducibility limit asgeneral guides, and the associated probability of 95 % as onlya rough indicator of what can be expected.13.2 BiasAt the time of the study, there was no acceptedreference material suitable for determining the bias for this testmet
36、hod, therefore no statement on bias is being made.13.3 The precision statement was determined through sta-tistical examination of 28 results, from four laboratories, onfour materials. These materials were described as follows:Sample 1: Low esters sample,Sample 2: High esters sample,Sample 3: Moderat
37、e esters sample, andSample 4: Elevated esters sample.13.4 To judge the equivalency of two test results, it isrecommended to choose the material closest in characteristicsto the test material.14. Keywords14.1 acid content; acidity; antifreeze; engine coolant; ester;ethylene glycol; glycol esterASTM I
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41、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
42、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 Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 2 Esters, ppmMateri
43、al Average,ARepeata-bilityStandardDeviation,Repro-ducibilityStandardDeviation,Repeata-bilityLimit,Repro-ducibilityLimit, SrSRrRSample17.25 1.41 5.22 3.96 14.62Sample2394.63 7.52 17.94 21.07 50.23Sample348.88 2.76 12.56 7.73 35.18Sample4203.50 1.12 11.30 3.13 31.65AThe average of the laboratories calculated averages.D7736 12 (2018)3
