1、Designation: D7736 11Standard 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, the year of last rev
2、ision. 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 This test method
3、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 in thisstandard.1.
4、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 and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Doc
5、uments2.1 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 Coolants3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method,
6、referto Terminology D4725.4. Summary of Test Method4.1 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
7、is heated at 100C to hydrolyze the esters. It is thenback-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 syste
8、m, the esters can hydro-lyze to form glycol and an acid. 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 co
9、lor change titration.Glycol with a strong color could 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 SolutionDisso
10、lve 0.5 g of phenol-phthalein in methanol or ethanol and dilute to 100 mL.8.2 Sodium Hydroxide (NaOH), 0.02 N in water.8.3 Sulfuric Acid (H2SO4), 0.02 N in water.8.4 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water as definedby Type II or III of
11、 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 the American Chemical Society,where such specifications are availa
12、ble.3Other grades may be1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and is the direct responsibility of Subcommittee D15.04 on ChemicalProperties.Current edition approved June 1, 2011. Published August 2011. DOI: 10.1520/D773611.2For referenced ASTM standards,
13、 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 Chemicals, American Chemical Society Specifications, AmericanChemical Society, Wash
14、ington, DC. For Suggestions on the testing of reagents notlisted by the American Chemical Society, see Annual Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.1Copyrigh
15、t ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.used, 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 a
16、ccordance with Practice 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 15seconds. Do
17、 not record this volume of titrant. Repeat for eachbottle.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 pin
18、k end point permanent 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 th
19、e trial suggestsconcentration 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 Nsod
20、ium hydroxide into each 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
21、 capsslightly loose to 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:% acet
22、ic acid 5mL NaOH! N NaOH!60.0 g/equivalent! 1 L/1000 mL!g of sample3 100where:N = normality of the NaOH used.11.2 Ester Content:% esters as acetic acid! 5B A! NH2SO4!60.0g/equivalent! 1 L/1000 mL!g of sample3 100esters, ppm as acetic acid! 5 % esters as acetic acid! 3 10 000where:N = normality of th
23、e H2SO4used,B =H2SO4used to titrate 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 an
24、d Bias13.1 Duplicate results for acidity should not differ by morethan 0.0003 %. Duplicate results for ester content should notdiffer by more than 15 ppm.14. Keywords14.1 acid content; acidity; antifreeze; engine coolant; ester;ethylene glycol; glycol esterTABLE 1 Recommended Sample SizesEstimated E
25、sterContent, wt %Sample Size, g Sample Method0.50 wt %” if the titration determination exceeds 0.50 %.D7736 112ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advise
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28、ou 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 standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individua
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