1、Designation:D773611 Designation: D7736 12Standard 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,
2、the 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 acids and glycol esters in ethylene glycol by titration.
3、1.2 This test method is for used on ethylene glycol used for the manufacture of engine coolant. It can not be used on formulatedengine coolant. The inhibitors will interfere with the determination.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are inc
4、luded in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior t
5、o use.2. Referenced Documents2.1 ASTM Standards:2D1176 Practice for Sampling and Preparing Aqueous Solutions of Engine Coolants or Antirusts for Testing PurposesD1193 Specification for Reagent WaterD4725 Terminology for Engine Coolants Terminology for Engine CoolantsE177 Practice for Use of the Term
6、s Precision and Bias in ASTM Test MethodsE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method3. Terminology3.1 Definitions:3.1.1 For definitions of terms used in this test method, refer to Terminology D4725.4. Summary of Test Method4.1 This test method is
7、 used to determine the acid and ester content of ethylene glycol by titration. The sample is titrated to thephenolphthalein end point with 0.02 N NaOH to determine the acidity. Then a known amount of base is added and the sample isheated at 100C to hydrolyze the esters. It is then back-titrated with
8、 0.02 N sulfuric acid to determine the ester content.5. Significance and Use5.1 The presence of acids or glycol esters in the ethylene glycol used to produce engine coolant is undesirable. Under conditionsin an engine cooling system, the esters can hydrolyze to form glycol and an acid. The acid will
9、 react with the corrosion inhibitors,thereby reducing the useful life of the coolant. This method can determine the amount of acid and glycol ester present in theethylene glycol.6. Interferences6.1 This test method is based on a color change titration. Glycol with a strong color could interfere with
10、 the results of thismethod.6.2 High pH recycled glycols streams will affect the results of this test method.1This test method is under the jurisdiction of ASTM Committee D15 on Engine Coolants and Related Fluids and is the direct responsibility of Subcommittee D15.04 onChemical Properties.Current ed
11、ition approved June 1, 2011. Published August 2011. DOI: 10.1520/D773611.Current edition approved April 1, 2012. Published June 2012. Originally approved in 2011. Last previous edition approved in 2011 as D7736 - 11. DOI:10.1520/D773612.2For referenced ASTM standards, visit the ASTM website, www.ast
12、m.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what
13、changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the o
14、fficial document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.7. Apparatus7.1 250 mL Borosilicate Glass Bottles, with screw caps.8. Reagents and Materials8.1 Phenolphthalein SolutionDissolve 0.5 g of phenolphthalein in methanol or
15、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, references to water shall be understood to mean reagent water as defined byType II or III of Specification D1193.8.5 Purity of ReagentsR
16、eagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available.3Other grades may be used, provided it i
17、s first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy of the determination.9. Sampling9.1 Sample the material in accordance with Practice D1176.10. Procedure10.1 Acid Content:10.1.1 Adjustment of pHPipet 25.00 mL of deionized water into e
18、ach of three 250 mL bottles.Add 3 drops of phenolphthaleinsolution to each. Titrate with 0.02 N sodium hydroxide to the first pink end point permanent for at least 15 seconds. Do not recordthis volume of titrant. Repeat for each bottle.10.1.2 Determination of Sample Acidity:10.1.2.1 Add an amount of
19、 sample as indicated in Table 1 to the 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 hydroxide to the first pink end point permanent for at least 15 s. This volumeof titrant is used to calculate the percent acid.NOTE 1If the ester
20、content is completely unknown, a trial titration beginning with 25 g of sample may be conducted to develop a preliminary estimatebefore the actual test titration is performed. If the trial suggests concentration of over 0.10 wt % (1000 ppm) then reduce the sample to 10 g and repeat.The second trial
21、should provide enough information to direct an 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 N sodium hydroxide into each bottle used in 10.1.2. Prepare a blankfor each sample by pipetting 25.00 mL of 0.02 N sodium
22、 hydroxide into three clean, 250 mL bottles. Immerse the pairs of bottlesin a boiling water bath for 1 h. (Tap water is suitable.) The weight of the bottles should prevent tipping. Leave caps slightly looseto prevent pressure buildup.10.2.2 Determination of the Ester ContentRemove bottles from the b
23、ath and cool to room temperature. When cool, add 3drops of phenolphthalein solution to each and titrate with 0.02 N H2SO4until disappearance of pink color.11. Calculation11.1 Acidity:% acetic acid 5mL NaOH! N NaOH!60.0 g/equivalent! 1 L/1000 mL!g of sample3 100D7736-12_13Reagent Chemicals, American
24、Chemical Society Specifications, American Chemical Society, Washington, DC. For Suggestions on the testing of reagents not listed bythe American Chemical Society, see Annual Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U
25、.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.TABLE 1 Recommended Sample SizesEstimated EsterContent, wt %Sample Size, g Sample Method0.50 wt %” if the titration determination exceeds 0.50 %.D7736 122where:N = normality of the NaOH used.11.2 Ester Content:D7736-12_2D7736-12_3where:N = nor
26、mality of the 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 of acidity as mass percent acetic acid.12.2 Report the average of the three determinations of the ester content as ppm acetic acid.13
27、. Precision and Bias13.1Duplicate results for acidity should not differ by more than 0.0003 %. Duplicate results for ester content should not differby more than 15 ppm.13.1 The precision of this test method is based on an interlaboratory study conducted in 2009. Each of four laboratories testedfour
28、different materials. Every “test result” represents an individual determination. All laboratories were asked to report duplicatetest results from a single operator for every material. Except for the limited number of laboratories involved, and the inability ofall participants to report all requested
29、 replicates, Practice E691 was followed for the design and analysis of the data; the detailsare given in RR:D15-1031.413.1.1 Repeatability Limit, rTwo test results obtained within one laboratory shall be judged not equivalent if they differ bymore than the r value for that material; r is the interva
30、l representing the critical difference between two test results for the samematerial, obtained by the same operator using the same equipment on the same day in the same laboratory.13.1.1.1 Repeatability limits are listed in Table 2.13.1.2 Reproducibility Limit, RTwo test results shall be judged not
31、equivalent if they differ by more than the R value for thatmaterial; R is the interval representing the critical difference between two test results for the same material, obtained by differentoperators using different equipment in different laboratories.13.1.2.1 Reproducibility limits are listed in
32、 Table 2.13.1.3 The above terms (repeatability limit and reproducibility limit) are used as specified in Practice E177.13.1.4 Any judgment in accordance with statements 13.1.1 and 13.1.2 would normally have an approximate 95% probabilityof being correct, however the precision statistics obtained in
33、this interlaboratory study (ILS) shall not be treated as exactmathematical quantities that are applicable to all circumstances and uses. The limited number of materials tested and laboratoriesreporting replicate results guarantees that there will be times when differences greater than predicted by t
34、he ILS results will arise,sometimes with considerably greater or smaller frequency than the 95% probability limit would imply. Consider the repeatabilitylimit and the reproducibility limit as general guides, and the associated probability of 95% as only a rough indicator of what canbe expected.13.2
35、BiasAt the time of the study, there was no accepted reference material suitable for determining the bias for this testmethod, therefore no statement on bias is being made.13.3 The precision statement was determined through statistical examination of 28 results, from four laboratories, on fourmateria
36、ls. These materials were described as follows:Sample 1: Low esters sample,4Supporting data have been filed at ASTM International Headquarters and may be obtained by requesting Research Report RR:D15-1031.TABLE 2 Esters, ppmMaterialAverage,xARepeatabilityStandardDeviation, SrReproducibilityStandardDe
37、viation, SRRepeatabilityLimit, rReproducibilityLimit, RSample 1 7.25 1.41 5.22 3.96 14.62Sample 2 394.63 7.52 17.94 21.07 50.23Sample 3 48.88 2.76 12.56 7.73 35.18Sample 4 203.50 1.12 11.30 3.13 31.65AThe average of the laboratories calculated averages.D7736 123Sample 2: High esters sample,Sample 3:
38、 Moderate esters sample, andSample 4: Elevated esters sample.13.4 To judge the equivalency of two test results, it is recommended to choose the material closest in characteristics to the testmaterial.14. Keywords14.1 acid content; acidity; antifreeze; engine coolant; ester; ethylene glycol; glycol e
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