1、Designation: D3242 11Designation: 354/98Standard Test Method forAcidity in Aviation Turbine Fuel1This standard is issued under the fixed designation D3242; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope*1.1 This test method covers the determination of the ac
3、idityin aviation turbine fuel in the range from 0.000 to 0.100 mgKOH/g.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 does not purport to address all of thesafety concerns, if any, associated with its use.
4、 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 Documents2.1 ASTM Standards:2D664 Test Method for Acid Number of Petroleum Productsby Potentiometric Titra
5、tionD1193 Specification for Reagent Water3. Terminology3.1 Definitions:3.1.1 acid number, nthe quantity of a specified base,expressed in milligrams of potassium hydroxide per gram ofsample, required to titrate a sample in a specified solvent to aspecified endpoint using a specified detection system.
6、3.1.1.1 Discussionin this test method, the solvent is atoluene-water-isopropanol mixture and the end point is deter-mined when a green/green brown color is obtained using thespecified p-naphtholbenzein indicator solution.4. Summary of Test Method4.1 The sample is dissolved in a mixture of toluene an
7、disopropyl alcohol containing a small amount of water. Theresulting single phase solution is blanketed by a stream ofnitrogen bubbling through it and is titrated with standardalcoholic potassium hydroxide to the end point indicated by thecolor change (orange in acid and green in base) of the addedp-
8、naphtholbenzein solution.5. Significance and Use5.1 Some acids can be present in aviation turbine fuels dueeither to the acid treatment during the refining process or tonaturally occurring organic acids. Significant acid contamina-tion is not likely to be present because of the many check testsmade
9、during the various stages of refining. However, traceamounts of acid can be present and are undesirable because ofthe consequent tendencies of the fuel to corrode metals that itcontacts or to impair the water separation characteristics of theaviation turbine fuel.5.2 This test method is designed to
10、measure the levels ofacidity that can be present in aviation turbine fuel and is notsuitable for determining significant acid contamination.6. Apparatus6.1 BuretA 25-mL buret graduated in 0.1-mL subdivi-sions, or a 10-mL buret graduated in 0.05-mL subdivisions.NOTE 1An automated buret capable of del
11、ivering titrant amounts in1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved May 1, 2011. Published July 2011. Originally approvedin 1973. Last
12、 previous edition approved in 2008 as D324208. DOI: 10.1520/D3242-11.This test method has been approved by the sponsoring committees and acceptedby the cooperating societies in accordance with established procedures.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
13、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshoh
14、ocken, PA 19428-2959, United States.0.05 mL or smaller increments can be used, but the stated precision datawere obtained using manual burets only.7. Reagents and Materials7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless otherwise indicated, it is intended thatall reag
15、ents shall conform to the specifications of the Commit-tee on Analytical Reagents of the 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 the
16、accuracy of the determination.NOTE 2Commercially available reagents may be used in place oflaboratory preparations when they are certified in accordance with 7.1.7.2 Purity of Water References to water shall be under-stood to mean distilled water as defined by Type III water ofSpecification D1193.7.
17、3 p-Naphtholbenzein4,5Indicator SolutionThep-naphtholbenzein must meet the specifications given inAnnexA1. Prepare a solution of p-naphtholbenzein in titration solventequal to 10 6 0.01 g/L.7.4 Nitrogen, dry-type, carbon dioxide-free. (WarningCompressed gas under high pressure. Gas reduces oxygenava
18、ilable for breathing.)7.5 Potassium Hydroxide Solution, Standard Alcoholic(0.01 N)Add 0.6 g of solid KOH (WarningHighly corro-sive to all body tissue both in solid form and in solution.) toapproximately 1 L of anhydrous isopropyl alcohol(WarningFlammable. Vapor harmful. Keep away from heat,sparks, a
19、nd open flame.) (containing less than 0.9 % water) ina 2-L Erlenmeyer flask. Boil the mixture gently for 10 to 15min, stirring to prevent the solids from forming a cake on thebottom. Add at least 0.2 g of barium hydroxide (Ba(OH)2)(WarningPoisonous if ingested. Strongly alkaline, causessevere irrita
20、tion producing dermatitis.) and again boil gentlyfor 5 to 10 min. Cool to room temperature, allow to stand forseveral hours, and filter the supernatant liquid through a finesintered-glass or porcelain filtering funnel; avoid unnecessaryexposure to carbon dioxide (CO2) during filtration. Store thesol
21、ution in a chemically resistant dispensing bottle out ofcontact with cork, rubber, or saponifiable stopcock lubricantand protected by a guard tube containing soda lime.NOTE 3Because of the relative large coefficient of cubic expansion oforganic liquids, such as isopropyl alcohol, the standard alcoho
22、lic solutionsshould be standardized at temperatures close to those employed in thetitration of samples.7.5.1 Standardization of Potassium Hydroxide SolutionStandardize frequently enough to detect changes of 0.0002N.One way to accomplish this is as follows. Weigh, to the nearest0.1 mg, approximately
23、0.02 g of potassium acid phthalate,which has been dried for at least1hat1106 1C and dissolvein 40 6 1 mL of water, free of CO2. Titrate with the potassiumhydroxide alcoholic solution to either of the following endpoints: (1) when the titration is electrometric, titrate to awell-defined inflection po
24、int at the voltage that corresponds tothe voltage of the basic buffer solution; (2) when the titrationis colorimetric, add 6 drops of phenolphthalein indicatorsolution and titrate to the appearance of a permanent pinkcolor. Perform the blank titration on the water used to dissolvethe potassium acid
25、phthalate. Calculate the normality using theequation:Normality 5Wp204.2331000V2Vb(1)where:Wp= weight of the potassium acid phthalate, g,204.23 = molecular weight of the potassium acid phthalate,V = volume of titrant used to titrate the salt to thespecific end point, mL, andVb= volume of titrant used
26、 to titrate the blank, mL.7.5.2 Phenolphthalein Indicator SolutionDissolve 0.1 g6 0.01 of pure solid phenolphthalein in 50 mL of water, free ofCO2, and 50 mL of ethanol.7.6 Titration SolventAdd 500 mL of toluene (WarningFlammable. Vapor harmful. Keep away from heat, sparks, andopen flame.) and 5 mL
27、of water to 495 mL of anhydrousisopropyl alcohol.8. Procedure8.1 Introduce 100 6 5 g of the sample weighed to thenearest 0.5 g, into a 500-mL wide-mouth Erlenmeyer flask.(One type of suitable modified flask is shown in Fig. 1.) Add100 mL of the titration solvent and 0.1 mL of the indicatorsolution.
28、Introduce nitrogen througha6to8mmoutsidediameter glass tube to a point within 5 mm of the flask bottomat a rate of 600 to 800 mL/min. Bubble the solution for 3 min6 30 s with occasional mixing.8.1.1 The vapor from this treatment contains toluene andshould be removed with adequate ventilation.3Reagen
29、t 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 Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand N
30、ational Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4In a 2006 study, only Kodak, Baker (Mallinkrodt), Fluka, and Aldrich werefound to meet the specifications in Annex A1. However, Kodak brand is no longeravailable.5Supporting data have been filed at ASTM International Headqu
31、arters and maybe obtained by requesting Research Report RR:D02-1626.FIG. 1 Titration FlaskD3242 1128.2 Continue the nitrogen addition and titrate without delayat a temperature below 30C. Add 0.01 N KOH solution inincrements and swirl to disperse. When the solution first turnsgreen, reduce the increm
32、ent size to dropwise (manual buret) orbetween 0.01 and 0.05 mL (automated buret). Continue until apersistent green end point is reached and held for a minimumof 15 s after the addition of the last increment.NOTE 4The temperature can be measured by any suitable temperaturemeasuring device.8.3 BlankPe
33、rform a blank titration on 100 mL of thetitration solvent and 0.1 mL of the indicator solution, introduc-ing the nitrogen in the same manner and titrating to the sameend point as above.9. Quality Control Checks9.1 Confirm the performance of the equipment or theprocedure each day it is in use, by ana
34、lyzing a quality control(QC) sample. It is advisable to analyze additional QC samplesas appropriate, such as at the end of a batch of samples or aftera fixed number of samples to ensure the quality of the results.Analysis of result(s) from these QC samples can be carried outusing control chart techn
35、iques.6When the QC sample resultcauses the laboratory to be in an out-of-control situation, suchas exceeding the laboratorys control limits, instrument recali-bration may be required. An ample supply of QC samplematerial shall be available for the intended period of use, andshall be homogeneous and
36、stable under the anticipated storageconditions. If possible, the QC sample shall be representativeof samples typically analyzed and the average value andcontrol limits of the QC sample shall be determined prior tomonitoring the measurement process. The QC sample preci-sion shall be checked against t
37、he ASTM method precision toensure data quality.NOTE 5Because the acid number can vary while the QC sample is instorage, when an out-of-control situation arises, the stability of the QCsample can be a source of the error.10. Calculations10.1 Calculate the acid number as follows:Acid number, mg of KOH
38、/g 5 A 2 B!N 3 56.1/W (2)where:A = KOH solution required for titration of the sample(8.2), mL,B = KOH solution required for titration of the blank (8.3),mL,N = normality of the KOH solution, andW = sample used, g.11. Report11.1 Report the result to the nearest 0.001 mg KOH/g asAcid Number (Test Meth
39、od D3242) = (Result).12. Precision and Bias712.1 PrecisionThe precision of this test method as deter-mined by statistical examination of interlaboratory results is asfollows:12.1.1 RepeatabilityThe difference between two test re-sults, obtained by the same operator with the same apparatusunder const
40、ant operating conditions on identical test material,would in the long run, in the normal and correct operation ofthe test method, exceed the following values only in one casein twenty (see Table 1).12.1.2 ReproducibilityThe difference between two singleand independent results obtained by different o
41、perators work-ing in different laboratories on identical test material would, inthe long run, in the normal and correct operation of the testmethod, exceed the following values only in one case in twenty(see Table 1).NOTE 6The precision statements were based on the use of manualburets only. The user
42、 is cautioned that the precision statements may ormay not be applicable to titrations performed with the use of automatedburets, since no interlaboratory study has been conducted to date tostatistically evaluate results determined by both techniques.12.2 BiasThe procedure in this test method has no
43、biasbecause the value of the acid can be defined only in terms ofthe test method.13. Keywords13.1 acidity; aviation turbine fuel6MNL 7, Manual on Presentation of Data Control Chart Analysis, Section 3:Control Charts for Individuals, 6th ed., ASTM International, W. Conshohocken,1990.7Supporting data
44、have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1010.TABLE 1 PrecisionANOTEAll values are in acid number units.Average Acid Number Repeatability Reproducibility0.001 0.0004 0.00130.002 0.0006 0.00180.005 0.0009 0.00290.010 0.0013 0.00410.020
45、 0.0019 0.00570.050 0.0030 0.00910.100 0.0042 0.0128AThese precision data were derived as follows:Repeatability = 0.0132 =aReproducibility = 0.0406 = awhere: a = acid numberD3242 113ANNEXES(Mandatory Information)A1. SPECIFICATIONS FOR p-NAPHTHOLBENZEINA1.1 Conformity RequirementsA1.1.1 AppearanceRed
46、 amorphous powder.A1.1.2 ChloridesLess than 0.5 %.A1.1.3 SolubilityTen grams shall dissolve completely in 1L of titration solvent.A1.1.4 Minimum AbsorbanceExactly 0.1000 g of thesample is dissolve in 250 mL of methanol. (WarningFlammable.) Five millilitres of this solution is made up to 100mL with p
47、H 12 buffer. This final dilution should have aminimum absorbance of 1.20 when read at the 650-nm peakusing a Beckman DU or alternative type spectrophotometer,1-cm cells, and water as the blank.A1.1.5 pH Range:A1.1.5.1 Indicator turns to the first clear green at a relativepH of 11 6 0.5 when tested b
48、y the method for pHr range ofp-naphtholbenzein indicator as described in Annex A2.A1.1.5.2 Requires not more than 0.5 mL of 0.01 N KOHsolution above that for the blank to bring the indicator solutionto the first clear green.A1.1.5.3 Requires not more than 1.0 mL of 0.01 N KOHsolution above that for
49、the blank to bring the indicator solutionto a blue color.A1.1.5.4 Initial pHr of the indicator solution is at least ashigh as that of the blank.A1.1.5.5 Buffer is made by mixing 50 mL of 0.05 M dibasicsodium phosphate with 26.9 mL 0.1 M sodium hydroxide.A2. TEST METHOD FOR DETERMINING pHr RANGE OF p-NAPHTHOLBENZEIN INDICATORA2.1 ScopeA2.1.1 This test method is intended for determining theacceptability of p-naphtholbenzein indicator for use in TestMethod D3242 with regard to color change over a pHr range.A2.2. TerminologyA2.2.1 Definitions of Te
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