1、Designation: D4739 11 (Reapproved 2017)D4739 17Standard Test Method forBase Number Determination by Potentiometric HydrochloricAcid Titration1This standard is issued under the fixed designation D4739; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、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.INTRODUCTIONCurrently, there are two ASTM test methods under the jurisdiction of Committee D02 used
3、fordetermining base number by potentiometric titration: Test Method D2896 and Test Method D4739.They are both used throughout the petroleum industry. Test Method D2896 is for new oils and is usedin setting specifications since it is more accurate than Test Method D4739. Test Method D4739 shallbe use
4、d exclusively for the purpose of tracking base number loss as an oil proceeds in service. In manycases, the test methods will provide different results. Some comparisons are given in the Scope andthe Significance and Use sections of this test method to distinguish between the two standards and topro
5、vide guidance to users.1. Scope Scope*1.1 This test method covers a procedure for the determination of basic constituents in petroleum products and new and usedlubricants. This test method resolves these constituents into groups having weak-base and strong-base ionization properties,provided the dis
6、sociation constants of the more strongly basic compounds are at least 1000 times than that of the next weakergroups. This test method covers base numbers up to 250.1.2 In new and used lubricants, the constituents that can be considered to have basic properties are primarily organic andinorganic base
7、s, including amino compounds. This test method uses hydrochloric acid as the titrant, whereas Test Method D2896uses perchloric acid as the titrant. This test method may or may not titrate these weak bases and, if so, it will titrate them to a lesserdegree of completion; some additives such as inhibi
8、tors or detergents may show basic characteristics.1.3 When testing used engine lubricants, it should be recognized that certain weak bases are the result of the service rather thanhaving been built into the oil. This test method can be used to indicate relative changes that occur in oil during use u
9、nder oxidizingor other service conditions regardless of the color or other properties of the resulting oil. The values obtained, however, areintended to be compared with the other values obtained by this test method only; base numbers obtained by this test method arenot intended to be equal to value
10、s by other test methods. Although the analysis is made under closely specified conditions, thistest method is not intended to, and does not, result in reported basic properties that can be used under all service conditions topredict performance of an oil; for example, no overall relationship is know
11、n between bearing corrosion or the control of corrosivewear in the engine and base number.1.4 This test method was developed as an alternative for the former base number portion of Test Method D664 (last publishedin Test Method D664 81).1.4.1 Colorimetric test methods for base number are Test Method
12、 D974, IP 139, and 5102.1 on acid and base number byextraction (color-indicator titration) of Federal Test Method Standard No. 791b. Test results by these methods may or may not benumerically equivalent to this test method.1.5 The values stated in SI units are to be regarded as standard. No other un
13、its of measurement are included in this standard.1.6 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 safety, health, and healthenvironmental practices and deter
14、mine theapplicability of regulatory limitations prior to use.1 This test method is under the jurisdiction ofASTM Committee D02 on Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Liquid Fuels and Lubricants.Current edition approve
15、d June 1, 2017Dec. 1, 2017. Published July 2017February 2018. Originally approved in 1987. Last previous edition approved in 20112017 asD4739 11.D4739 11 (2017). DOI: 10.1520/D4739-11R17.10.1520/D4739-17.This document is not an ASTM standard and is intended only to provide the user of an ASTM standa
16、rd an indication of what 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
17、is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States11.7 This international standard was developed in accordance with internationall
18、y recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D664 Test Method
19、 for Acid Number of Petroleum Products by Potentiometric TitrationD974 Test Method for Acid and Base Number by Color-Indicator TitrationD1193 Specification for Reagent WaterD2896 Test Method for Base Number of Petroleum Products by Potentiometric Perchloric Acid TitrationD4057 Practice for Manual Sa
20、mpling of Petroleum and Petroleum ProductsD4177 Practice for Automatic Sampling of Petroleum and Petroleum Products2.2 IP Standard:3IP 139 Petroleum products and lubricantsDetermination of acid and base numberColour-indicator titration method2.3 U.S. Federal Test Method:4Federal Test Method Standard
21、 No. 791b Lubricants Liquid Fuels and Related Products; Methods of Testing3. Terminology3.1 Definitions:3.1.1 base number, nthe quantity of a specified acid, expressed in terms of the equivalent number of milligrams of potassiumhydroxide per gram of sample, required to titrate a sample in a specifie
22、d solvent to a specified endpoint using a specified detectionsystem.3.1.1.1 DiscussionIn this test method, the sample is titrated to a meter reading corresponding to aqueous acidic buffer solution or appropriateinflection point.3.2 Definitions of Terms Specific to This Standard:3.2.1 strong base num
23、ber, nthe quantity of acid, expressed in terms of the equivalent number of milligrams of potassiumhydroxide per gram of sample, that is required to titrate a sample dissolved in the specified solvent from the initial meter readingto a meter reading corresponding to a basic buffer solution.4. Summary
24、 of Test Method4.1 The sample is dissolved in a mixture of toluene, propan-2-ol (isopropyl alcohol), chloroform, and a small amount of waterand titrated potentiometrically with alcoholic hydrochloric acid solution. The test results of this procedure are obtained by titrationmode of fixed increment a
25、nd fixed time additions of the titrant. An endpoint is selected from a titration curve according to thecriteria given in Section 12 and used to calculate a base number.5. Significance and Use5.1 New and used petroleum products can contain basic constituents that are present as additives. The relativ
26、e amount of thesematerials can be determined by titration with acids. The base number is a measure of the amount of basic substances in the oilalways under the conditions of the test. It is sometimes used as a measure of lubricant degradation in service. However, anycondemning limit shall be empiric
27、ally established.5.2 As stated in 1.2, this test method uses a weaker acid to titrate the base than Test Method D2896, and the titration solventsare also different. Test Method D2896 uses a stronger acid and a more polar solvent system than Test Method D4739. As a result,Test Method D2896 will titra
28、te salts of weak acids (soaps), basic salts of polyacidic bases, and weak alkaline salts of some metals.They do not protect the oil from acidic components due to the degradation of the oil. This test method may produce a falselyexaggerated base number. Test Method D4739 will probably not titrate the
29、se weak bases but, if so, will titrate them to a lesserdegree of completion. It measures only the basic components of the additive package that neutralizes acids. On the other hand, ifthe additive package contains weak basic components that do not play a role in neutralizing the acidic components of
30、 the degradingoil, then the Test Method D4739 result may be falsely understated.5.3 Particular care is required in the interpretation of the base number of new and used lubricants.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org.
31、 For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Available from Energy Institute, 61 New Cavendish St., London, W1G 7AR, U.K., http:/www.energyinst.org.4 Available from Standardization Documents Order Desk, DODSSP, Bldg. 4, Sect
32、ion D, 700 Robbins Ave., Philadelphia, PA 19111-5098.D4739 1725.3.1 When the base number of the new oil is required as an expression of its manufactured quality, Test Method D2896 ispreferred, since it is known to titrate weak bases that this test method may or may not titrate reliably.5.3.2 When th
33、e base number of in-service or at-term oil is required, this test method is preferred because in many cases,especially for internal combustion engine oils, weakly basic degradation products are possible. Test Method D2896 will titratethese, thus giving a false value of essential basicity. This test
34、method may or may not titrate these weak acids.5.3.3 When the loss of base number value, as the oils proceed in service, is the consideration, this test method is to be preferredand all values including the unused oil shall be determined by this test method. Base numbers obtained by this test method
35、 shallnot be related to base numbers obtained by another test method such as Test Method D2896.5.3.4 In ASTM Interlaboratory Crosscheck Programs for both new and used lubricants, historically Test Method D2896 givesa higher value for base number.6. Apparatus6.1 Potentiometric Titration, automatic or
36、 manual, with capability of adding fixed increments of titrant at fixed time intervals(see Annex A1).6.1.1 The titrimeter must automatically (or manually) control the rate of addition of titrant as follows: Delivery of titrant willbe incremental; after delivery of precisely a 0.100 mL increment (see
37、 6.1.2), the delivery is stopped and a fixed time period of 90 sis allowed to pass before another 0.100 mL increment of titrant is delivered. This procedure is repeated until the titration iscompleted.6.1.2 The precision of addition of the 0.100 mL increments of titrant must be 60.001 mL for automat
38、ic titrators. For manualburet, it should be 60.005 mL. A higher incremental precision is required for an automatic buret, because the total volume to theend point is summed from the individual increments; it is read from a scale with a manual buret.6.2 Sensing Electrode, standard pH with glass membr
39、ane, suitable for non-aqueous titrations.6.3 Reference Electrode, Silver/Silver Chloride (Ag/AgCl) reference electrode with sleeve junction, filled with 1 M to 3 M LiClin ethanol.6.3.1 Combination ElectrodeSensing electrodes may have theAg/AgCl reference electrode built into the same electrode body,
40、which offers the convenience of working with and maintaining only one electrode. The combination electrode shall have a sleevejunction type of reference and shall use an inert ethanol electrolyte, for example, 1 M to 3 M LiCl in ethanol. In the referencecompartment, the sensing electrode part shall
41、use a glass membrane designed for non-aqueous titrations. These combinationelectrodes shall have the same response or better response than a dual electrode system. They shall have removable sleeves foreasy rinsing and addition of electrolyte. (WarningWhen a movable sleeve is part of the electrode sy
42、stem, ensure that the sleeveis unimpaired before every titration.)6.4 Stirrer, Buret, Stand, Titration Vessel, as specified in Annex A1, are required.7. Reagents7.1 Purity of ReagentsReagent-grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that allreagents shall
43、 conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available.5 Other grades may be used, provided it is first ascertained that the reagent is of sufficiently highpurity to permit its use without lessening the accuracy
44、 of the determination.7.2 Purity of WaterUnless otherwise indicated, references to water shall be understood to mean reagent water that meets therequirement of either Type I, II, or III of Specification D1193.7.3 Buffer, Aqueous AcidCommercial pH 3 buffer solution with a tolerance of 60.02 pH units
45、at 25 C. This solution shallbe replaced at regular intervals consistent with its stability or when contamination is suspected. Information related to the stabilityshould be obtained from the manufacturer.7.4 Buffer, Aqueous BasicCommercial pH 10 buffer solution with a tolerance of 60.02 pH units at
46、25 C. This solution shallbe replaced at regular intervals consistent with its stability or when contamination is suspected. Information related to the stabilityshould be obtained from the manufacturer.7.5 ChloroformReagent grade. (WarningToxic and suspected carcinogen.)7.6 Hydrochloric Acid Solution
47、, Standard Alcoholic (0.1 M)Mix 9 mL of reagent grade hydrochloric acid (HCl, sp gr 1.19)(WarningToxic and corrosive), with 1 L of anhydrous isopropyl alcohol. Standardize frequently enough to detect normalitychanges of 0.0005 by potentiometric titration of approximately 8 mL (accurately measured) o
48、f the 0.1 M alcoholic KOH solutiondiluted with 125 mL CO2-free water.5 Reagent Chemicals, American 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 Ch
49、emicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.D4739 1737.7 Ethanolreagent grade. (WarningFlammable and toxic, especially when denatured.)7.8 Lithium Chloride Electrolyte ElectrolytePrepare a solution of 1 M to 3 M LiCl in ethanol.7.9 Potassium Hydroxide(WarningCauses severe burns.)7.10 Potassium Hydroxide Solution, Standard Alcoholic (0.1 M)Add 6 g of reagent grade potassium hydroxide (KOH)(WarningToxic and corrosive), to approximately 1 L o
