1、Designation: D 3339 07An American National StandardStandard Test Method forAcid Number of Petroleum Products by Semi-Micro ColorIndicator Titration1This standard is issued under the fixed designation D 3339; the number immediately following the designation indicates the year oforiginal adoption or,
2、in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method covers the determination of acidicconstituents in new or used
3、petroleum products and lubricantssoluble or nearly soluble in mixtures of toluene, and isopropylalcohol. The test method is especially intended for cases inwhich the amount of sample available to be analyzed is toosmall to allow accurate analysis by Test Methods D 974 orD 664. It is applicable for t
4、he determination of acids havingdissociation constants in water larger than 109. Extremelyweak acids having dissociation constants smaller than 109donot interfere. Salts titrate if their hydrolysis constants are largerthan 109.1.2 This test method can be used to indicate relative changesin acid numb
5、er that occur in an oil during use under oxidizingconditions. Although the titration is made under definiteequilibrium conditions, the method does not measure anabsolute acidic property that can be used to predict perfor-mance of an oil under service conditions. No general relation-ship between bear
6、ing corrosion and acid number is known.1.3 Since this test method requires substantially less samplethan Test Methods D 974 or D 664, it provides an advanta-geous means of monitoring an oxidation test by changes in acidnumber by (1) minimizing test sample depletion for acidnumber analyses and thus m
7、inimizing the disturbance of thetest or (2) allowing additional acid number analyses to be madewhile maintaining the same test sample depletion and thusproviding additional data.NOTE 1Some oils, such as many cutting oils, rust-proofing oils, andsimilar compounded oils, or excessively dark-colored oi
8、ls, may be moredifficult to analyze by this test method due to obscurity of the color-indicator end point. These oils can be analyzed by Test Method D 664provided sufficient sample is available. However, this situation is muchless likely using Test Method D 3339 than using Test Method D 974 dueto th
9、e use of a more highly dilute sample during the titration and due tothe greater stability of the end point color change. The acid numbersobtained by Test Method D 3339 may or may not be numerically the sameas those obtained by Test Method D 664 but they should be of the sameorder of magnitude.NOTE 2
10、The results obtained using this method have been found to benumerically the same as those obtained using Test Method D 974, withinthe precision of the two methods, for new or oxidized lubricants of thetype primarily intended for hydraulic or steam turbine type service. Theoxidized lubricants were ob
11、tained using the Test Method D 943 oxidationtest. This correlation is shown by the correlation coefficient r = 0.989 withslope s = + 1.017 and intercept y = + 0.029, calculated using the acidnumbers obtained using both titration methods for the samples used for theprecision statement (12.2).21.4 The
12、 values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.5 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-pria
13、te safety and health practices and determine the applica-bility of regulatory limitations prior to use. For specificwarning statements, see Sections 7 and 9, A1.1.4, A2.3.1, andA2.10.1.2. Referenced Documents2.1 ASTM Standards:3D 664 Test Method forAcid Number of Petroleum Productsby Potentiometric
14、TitrationD 943 Test Method for Oxidation Characteristics of Inhib-ited Mineral OilsD 974 Test Method for Acid and Base Number by Color-Indicator TitrationD 1193 Specification for Reagent Water3. Terminology3.1 Definitions:1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum
15、Products and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved Nov. 1, 2007. Published November 2007. Originallyapproved in 1974. Last previous edition approved in 2004 as D 333904.2Use of the correlation coefficient is given in Mack
16、, C., Essentials of Statisticsfor Scientists and Technologists, Plenum Press, New York, NY, 1967, or otherpublications on statistics.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume infor
17、mation, 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 Conshohocken, PA 19428-2959, United States.3.1.1 acid number, nthe quantity of base, expre
18、ssed inmilligrams of potassium hydroxide per gram of sample, that isrequired to titrate a sample dissolved in a specified solvent toa specified end point.3.1.1.1 DiscussionIn this test method, acids or salts withdissociation constants greater than 109, are titrated to a greenend point with p-naphtho
19、lbenzein indicator.3.1.2 used oil, nany oil that has been in a piece ofequipment (for example, an engine, gearbox, transformer orturbine) whether operated or not.3.1.2.1 DiscussionTypically, in this test method, the acid-ity of oxidized hydraulic or steam turbine oils is measured.4. Summary of Test
20、Method4.1 To determine the acid number a sample of the oil isdissolved in a solvent consisting of toluene, isopropyl alcohol,and a small amount of water. The resulting single-phasesolution is titrated at room temperature under a nitrogenatmosphere with standardized 0.01 M potassium hydroxide(KOH) in
21、 isopropyl alcohol to the stable green color of theadded p-naphtholbenzein indicator.5. Significance and Use5.1 This test method measures the acid number of oilsobtained from laboratory oxidation tests using smaller amountsof sample than Test Methods D 974 or D 664. It has specificapplication in Tes
22、t Method D 943 in which small aliquots of oilare periodically removed for testing by Test Method D 3339.This test method, therefore, provides a means of monitoring therelative oxidation of oils, by measuring changes in acidnumber, at different time intervals and under the variousoxidizing test condi
23、tions.6. Apparatus (Refer to Fig. 1)6.1 Titration BuretA micro scale, automatic buret with0.01 mL subdivisions and at least a 2-mL buret capacity.6.2 Titrant ReservoirThe preferred reservoir is one that isintegral with the automatic buret, such as shown in Fig. 1.Atitrant reservoir separate from the
24、 automatic buret may be usedif the line connecting the reservoir with the buret is all glass.Exposure of the titrant to light should be minimized by use ofamber glass for the reservoir, by wrapping the reservoir withfoil such as aluminum foil, or by other suitable means. Also,the tube in the reservo
25、ir for titrant withdrawal is adjusted sothat the end of the tube is about 20 mm (0.8 in.) from thebottom of the reservoir so that any precipitate that may collecton the bottom of the reservoir will not be disturbed. To furtheravoid disturbing any precipitate in the reservoir, movement ofthe reservoi
26、r must be minimized.6.2.1 With either type of reservoir all entrances and exits tothe buret and reservoir must be connected to absorption tubesto remove atmospheric carbon dioxide and water, for example,tubes containing 10 to 20-mesh anhydrous calcium sulfate asdesiccant and soda-lime as carbon diox
27、ide absorbent. Precau-tions must be taken to prevent introduction of any soda-limeinto the titrant reservoir or buret.6.3 Titration Beaker100-mL capacity tall-form Berzeliusbeaker without pouring spout. Approximate dimensions are 47mm in inside diameter and 79 mm in height.6.4 Titration Beaker Purgi
28、ng StopperAstopper to enclosethe titration beaker. The stopper must be composed of anelastomeric material, such as neoprene, that is essentiallyunaffected by the titration solvent. Approximate stopper di-mensions are 53 mm top diameter, 45 mm bottom diameter,and 25 mm height. The stopper is fitted w
29、ith a 8-mm (0.3-in.)outside diameter glass inlet tube extending 15 6 2 mm beyondthe bottom of the stopper and with a 7 6 1-mm inside diameterhole.The inlet tube and hole are placed on opposite sides of thestopper with a center-to-center separation distance of 30 6 1mm.6.5 Purge Gas Rotameter, capabl
30、e of indicating a flow rateof 10 L/h.6.6 Stirrer Motor, variable speed, magnetically linked.NOTE 3A propeller may also be used instead of a magnetic stirrer tomix the samples.6.7 Stirring Bar, cylindrical, TFE-fluorocarbon encased,25.4 mm long and 7.9 mm in diameter.6.8 Pipet, capable of transferrin
31、g 0.100 6 0.002 mL oftitration indicator solution.6.9 Titration Solvent BuretA 500-mL or larger capacityburet with 5-mLsubdivisions. The top of the buret is stopperedand connected with an absorption tube, as in 6.2, to removeatmospheric carbon dioxide and water.An alternative means ofdispensing the
32、titration solvent may be used provided adispensing repeatability within 6 1 mLfor 40 mLis obtainableand the solvent in the dispenser is isolated from atmosphericcarbon dioxide and water.NOTE 4An automated photometric device may also be used fordetecting the titration end point. However, the precisio
33、n estimates given inSection 13 may not apply to this mode of titration.7. Reagents and Materials7.1 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 Rea
34、gents of the American Chemical Society,where such specifications are available or to other suchrecognized standards for reagent chemicals.4Other grades maybe used, provided it is first ascertained that the reagent is ofsufficient high purity to permit its use without lessening theaccuracy of the det
35、ermination.7.2 Purity of WaterAll references to water shall beunderstood to mean freshly distilled (carbon dioxide-free)water conforming to Specification D 1193, Type II or III.7.3 Ethyl Alcohol(WarningFlammable. DenaturedCannot be made nontoxic.) USP 200 proof or denaturedalcohol according to Formu
36、la 30 of the U. S. Bureau of InternalRevenue.7.4 Propanol-2-ol, (Isopropyl Alcohol) Anhydrous,(WarningFlammable, see also Note 5.) containing less than0.9 % water.4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of
37、 reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D3339072NOTE 5It has been reported that, if not inhibi
38、ted against it, propanol-2-ol can contain peroxides. When this occurs, an explosive mixture ispossible when the storage vessel or other equipment such as a dispensingbottle, are near empty and approaching dryness.7.5 p-Naphtholbenzein Indicator5,6SolutionThep-naphtholbenzein must meet the specificat
39、ions given inAnnexA1. Prepare a solution containing 10 g of p-naphtholbenzeinper litre of titration solvent.7.6 Nitrogen, dry and carbon dioxide-free.7.6.1 In order to obtain repeatable results and a stable endpoint color change, it is especially important that the nitrogenpurge gas be free of carbo
40、n dioxide. Prepurified grade nitrogenhas been found to be satisfactory.5In a 2006 study, only Kodak, Baker (Mallinkrodt), Fluka, and Aldrich werefound to meet the specifications in Annex A1. However, Kodak brand is no longeravailable.6Supporting data have been filed at ASTM International Headquarter
41、s and maybe obtained by requesting Research Report RR: D021626.FIG. 1 Schematic Drawing of Typical ApparatusD33390737.7 Phenolphthalein Indicator SolutionDissolve 0.10 g ofsolid pure phenolphthalein in 50 mL of water and 50 mL ofethyl alcohol.7.8 Titration SolventConsisting of 5.0 6 0.1 mL of water,
42、495 6 1 mL of anhydrous propanol-2-ol, and 500 6 1mLoftoluene.7.9 Potassium Hydroxide Solution, Standard Alcoholic(0.01 M) (WarningCorrosive.).NOTE 6Commercially available reagents may be used in place oflaboratory preparations.7.9.1 PreparationAdd3gofsolid KOH to approximately1 Lof anhydrous propan
43、ol-2-ol (isopropyl alcohol) (containingless than 0.9 % water) in a 2-L Erlenmeyer flask. Boil themixture gently on a steam bath for 10 to 15 min while stirringto prevent caking of solids on the bottom of the flask. Addabout1gofbarium hydroxide and again boil gently for about10 min. Cool to room temp
44、erature, stopper to prevent contactwith the room atmosphere and allow to stand overnight (about16 h). Filter the supernatant liquid through a 10-m TFE-fluorocarbon membrane filter while avoiding unnecessary ex-posure to the atmosphere and then dilute the solution (approxi-mately 0.05 M) with anhydro
45、us isopropyl alcohol to a totalvolume of about 5 L (Note 7). Store the titrant in a chemicallyresistant dispensing bottle out of contact with cork, rubber, orsaponifiable stopcock lubricant and protected by a guard tubecontaining soda-lime. Minimize exposure of the titrant to lightby storing in the
46、dark or in an amber bottle or by wrapping thebottle with aluminum foil.NOTE 7Care should be taken to ensure a final normality of 0.011 60.002.NOTE 8Because of the relatively large coefficient of cubic expansionof organic liquids, such as propanol-2-ol, the standard alcoholic solutionsshould be stand
47、ardized at temperatures close to those employed in thetitrations of samples.7.9.2 StandardizationThe titrant is standardized (Note 8)against dried (at least 1 h at 110C), pure potassium hydrogenphthalate using the method described in 9.1 for the acidnumber analysis, with the exception that water (40
48、 6 1 mL) isused as the solvent and 6 drops of phenolphthalein solution isused as the indicator. The blank is obtained in the same mannerexcept that the potassium hydrogen phthalate is excluded.Standardize the titrant frequently enough to detect changes of0.0003 M. The mean molarity determined by at
49、least duplicateanalyses is used as the titrant molarity for the acid numbercalculations.7.10 Toluene (WarningFlammable. Vapor harmful.)Nitration-grade, or equivalent.8. Preparation of Used Oil Samples8.1 Strict observance of the sampling procedure describedin 8.2 is necessary, since the sediment itself is acidic or basicor has adsorbed acidic or basic material from the sample.Failure to obtain a representative sample causes serious errors.8.2 Heat the sample (Note 9) of used oil to 60 6 5C in theoriginal container and agitate until all sediment is
