1、Designation: D 3339 08An 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 () 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 p
3、etroleum 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 th
4、e 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 numbe
5、r 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 beari
6、ng 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 mi
7、nimizing 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 oil
8、s, 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 the
9、 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 2T
10、he 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 obt
11、ained 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 asstandard. No other units of measurement are included in thisstandard.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-priate
13、 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 Ti
14、trationD 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 Pr
15、oducts and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved July 1, 2008. Published August 2008. Originallyapproved in 1974. Last previous edition approved in 2007 as D 333907.2Use of the correlation coefficient is given in Mack, C.
16、, 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 informati
17、on, 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, expressed
18、 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-naphtholben
19、zein 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 Meth
20、od4.1 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 iso
21、propyl 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 Test Me
22、thod 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 condition
23、s.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 aut
24、omatic 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 reservoir f
25、or titrant withdrawal is adjusted sothat the end of the tube is about 20 mm from the bottom of thereservoir so that any precipitate that may collect on the bottomof the reservoir will not be disturbed. To further avoiddisturbing any precipitate in the reservoir, movement of thereservoir must be mini
26、mized.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 dioxide absorbent.
27、 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 Purging StopperAsto
28、pper 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 with a 8-mm out
29、sidediameter glass inlet tube extending 15 6 2 mm beyond thebottom 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, capable of indicating a flow r
30、ateof 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 transferring 0.100 6 0.002 mL oftit
31、ration 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 titration solvent may be
32、 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 precision estimates given inSect
33、ion 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 Reagents of the American Ch
34、emical 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 determination.7.2 Purity of
35、 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 Formula 30 of the U. S. Burea
36、u 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 reagents notlisted by t
37、he 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.D3339082NOTE 5It has been reported that, if not inhibited against it, propanol
38、-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 specifications given inAnnexA1. Pr
39、epare 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 carbon dioxide. Prepurified g
40、rade 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 Headquarters and maybe obtained by
41、requesting Research Report RR: D021626.FIG. 1 Schematic Drawing of Typical ApparatusD33390837.7 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,495 6 1 mL of anhydrous
42、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 Preparation,Add3gofsolid KOH to approximately1 Lof anhydrous propanol-2-ol (isopropyl alcoh
43、ol) (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 temperature, stopper to prev
44、ent 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 anhydrous isopropyl alcohol to
45、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 dark or in an amber bott
46、le 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 standardized at temperatures
47、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 6 1 mL) isused as the s
48、olvent 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 least duplicateanalyses
49、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 homoge-neously suspende
