1、Designation: D974 14Designation: 139/98Standard Test Method forAcid and Base Number by Color-Indicator Titration1This standard is issued under the fixed designation D974; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of
2、last revision. 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 U.S. Department of Defense.1. Scope*1.1 This test method covers the det
3、ermination of acidic orbasic constituents (Note 1) in petroleum products2and lubri-cants soluble or nearly soluble in mixtures of toluene andisopropyl alcohol. It is applicable for the determination of acidsor bases whose dissociation constants in water are larger than109; extremely weak acids or ba
4、ses whose dissociationconstants are smaller than 109do not interfere. Salts react iftheir hydrolysis constants are larger than 109.NOTE 1In new and used oils, the constituents considered to haveacidic characteristics include organic and inorganic acids, esters, phenoliccompounds, lactones, resins, s
5、alts of heavy metals, and addition agentssuch as inhibitors and detergents. Similarly, constituents considered tohave basic properties include organic and inorganic bases, aminocompounds, salts of weak acids (soaps), basic salts of polyacidic bases,salts of heavy metals, and addition agents such as
6、inhibitors anddetergents.NOTE 2This test method is not suitable for measuring the basicconstituents of many basic additive-type lubricating oils. Test MethodD4739 can be used for this purpose.1.2 This test method can be used to indicate relative changesthat occur in an oil during use under oxidizing
7、 conditions.Although the titration is made under definite equilibriumconditions, the method does not measure an absolute acidic orbasic property that can be used to predict performance of an oilunder service conditions. No general relationship betweenbearing corrosion and acid or base numbers is kno
8、wn.NOTE 3Oils, such as many cutting oils, rustproofing oils, and similarcompounded oils, or excessively dark-colored oils, that cannot be ana-lyzed for acid number by this test method due to obscurity of thecolor-indicator end point, can be analyzed by Test Method D664. The acidnumbers obtained by t
9、his color-indicator test method need not benumerically the same as those obtained by Test Method D664, the basenumbers obtained by this color indicator test method need not benumerically the same as those obtained by Test Method D4739, but theyare generally of the same order of magnitude.1.3 The val
10、ues stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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 sa
11、fety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D117 Guide for Sampling, Test Methods, and Specificationsfor Electrical Insulating Oils of Petroleum OriginD664 Test Method for Acid Number of Petroleum Produc
12、tsby Potentiometric TitrationD1193 Specification for Reagent WaterD4175 Terminology Relating to Petroleum, PetroleumProducts, and LubricantsD4739 Test Method for Base Number Determination byPotentiometric Hydrochloric Acid Titration3. Terminology3.1 Definitions:3.1.1 acid number, nthe quantity of a
13、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.3.1.1.1 DiscussionIn this test method, the indicator isp-naphtholbenzein titrated to a green/green-brown end
14、point ina toluene-water-isopropanol solvent.3.1.2 base number, nthe quantity of a specified acid,expressed in terms of the equivalent number of milligrams ofpotassium hydroxide per gram of sample, required to titrate a1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Prod
15、ucts, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.In the IP, this test method is under the jurisdiction of the StandardizationCommittee. This test method was adopted as a joint ASTM-IP standard in 1965.Current edition
16、 approved Dec. 1, 2014. Published January 2015. Originallyapproved in 1948. Last previous edition approved in 2012 as D974 12. DOI:10.1520/D0974-14.2Statements defining this test method, its modification, and its significance whenapplied to electrical insulating oils of mineral origin will be found
17、in Guide D117.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.*A Summary of Changes section appears at the en
18、d of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1sample in a specified solvent to a specified endpoint using aspecified detection system.3.1.2.1 DiscussionIn this test method, the indicator isp-naphtholbenzein titrate
19、d to an orange end point in a toluene-water-isopropanol solvent.3.1.3 used oil, nany oil that has been in a piece ofequipment (for example, an engine, gearbox, transformer, orturbine) whether operated or not. D41753.2 Definitions of Terms Specific to This Standard:3.2.1 strong acid number, nthe quan
20、tity of base, expressedin milligrams of potassium hydroxide per gram of sample, thatis required to titrate a hot water extract of the sample to agolden-brown end point using methyl orange solution.4. Summary of Test Method4.1 To determine the acid or base number, the sample isdissolved in a mixture
21、of toluene and isopropyl alcoholcontaining a small amount of water, and the resulting single-phase solution is titrated at room temperature with standardalcoholic base or alcoholic acid solution, respectively, to theend point indicated by the color change of the addedp-naphtholbenzein solution (oran
22、ge in acid and green-brown inbase). To determine the strong acid number, a separate portionof the sample is extracted with hot water and the aqueousextract is titrated with potassium hydroxide solution, usingmethyl orange as an indicator.5. Significance and Use5.1 New and used petroleum products can
23、 contain basic oracidic constituents that are present as additives or as degrada-tion products formed during service, such as oxidation prod-ucts. The relative amount of these materials can be determinedby titrating with acids or bases. This number, whether ex-pressed as acid number or base number,
24、is a measure of thisamount of acidic or basic substances, respectively, in theoilalways under the conditions of the test. This number isused as a guide in the quality control of lubricating oilformulations. It is also sometimes used as a measure oflubricant degradation in service; however, any conde
25、mninglimits must be empirically established.5.2 Since a variety of oxidation products contribute to theacid number and the organic acids vary widely in corrosiveproperties, the test cannot be used to predict corrosiveness ofan oil under service conditions. No general correlation isknown between acid
26、 number and the corrosive tendency of oilstoward metals. Compounded engine oils can and usually dohave both acid and base numbers in this test method.6. Apparatus6.1 Burets (with the following dimensions):50 mL buret graduated in 0.1 mL subdivisions10 mL buret graduated in 0.05 mL or smaller subdivi
27、sions5 mL with 0.02 mL subdivisionsNOTE 4An automated buret capable of delivering titrant amounts in0.05 mL or smaller increments can be used but the stated precision datawere obtained using manual burets only.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless
28、 otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently hi
29、gh purity to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterReferences to water shall be under-stood to mean reagent water that meets the requirements ofeither Type I, II, or III of Specification D1193.7.3 Isopropyl Alcohol, anhydrous (less than 0.9 % water).(Wa
30、rning Flammable.)7.4 Hydrochloric Acid Solution, Standard Alcoholic(0.1 M)Mix 9 mL of concentrated hydrochloric acid(WarningCorrosive, fumes cause irritation) (HCl, sp gr1.19) with 1000 mL of anhydrous isopropyl alcohol (2-propanol) (WarningSee 7.3). Standardize frequently enoughto detect molarity c
31、hanges of 0.0005 (Note 6), preferably byelectrometric titration of approximately 8 mL (accurately mea-sured) of the 0.1 M alcoholic KOH solution diluted with125 mL of carbon dioxide-free water. When an electrometrictitration is used for the standardization, the end point shall bea well-defined infle
32、ction point closest to the cell voltage for theacidic buffer solution. When a colorimetric titration is used forthe standardization, titrate to the first stable appearance of theorange color with methyl orange indicator.NOTE 5Commercially available reagents may be used in place of thelaboratory prep
33、arations when they are certified to be in accordance with7.1.NOTE 6To simplify calculations, both the standard KOH and HClsolutions can be adjusted so that 1.00 mL is equivalent to 5.00 mg ofKOH. Sodium hydroxide (NaOH) and sulfuric acid (H2SO4) can besubstituted for KOH and HCl, respectively.7.5 Me
34、thyl Orange Indicator SolutionDissolve 0.1 g ofmethyl orange in 100 mL of water.7.6 p-Naphtholbenzein Indicator5,6SolutionThep-naphtholbenzein shall meet the specifications given in AnnexA1. Prepare a solution of p -naphtholbenzein in titrationsolvent equal to 10 L 6 0.01 gL.7.7 Potassium Hydroxide
35、Solution, Standard Alcoholic(0.1 M)Add 6 g of solid KOH (WarningHighly corrosiveto all body tissue) to approximately 1 Lof anhydrous isopropylalcohol (containing less than 0.9 % water) in a 2 L Erlenmeyerflask. Boil the mixture gently for 10 min to 15 min, stirring to4Reagent Chemicals, American Che
36、mical 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 National Formulary, U.S. P
37、harmacopeial Convention, Inc. (USPC), Rockville,MD.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
38、 by requesting Research Report RR:D02-1626.D974 142prevent the solids from forming a cake on the bottom. Add atleast 2 g of barium hydroxide (Ba(OH)2)(WarningPoisonous if ingested, strongly alkaline, causes severe irritationproducing dermatitis) and again boil gently for 5 min to10 min. Cool to room
39、 temperature, allow to stand for severalhours, and filter the supernatant liquid through a fine sintered-glass or porcelain filtering funnel; avoid unnecessary exposureto carbon dioxide (CO2) during filtration. Store the solution ina chemically resistant dispensing bottle out of contact withcork, ru
40、bber, or saponifiable stopcock lubricant and protectedby a guard tube containing soda lime or soda nonfibroussilicate absorbent (Ascarite, Carbosorb, or Indecarb).7.7.1 Standardization of Potassium Hydroxide SolutionStandardize frequently enough to detect changes of 0.0005 M.One way to do this is as
41、 follows: Weigh, to the nearest 0.1 mgapproximately 0.2 g of potassium acid phthalate, which hasbeen dried for at least 1 h at 110 C 6 1 C and dissolve in40 mL 6 1 mL of water, free of CO2. Titrate with thepotassium hydroxide alcoholic solution to either of the follow-ing end points: (1) When the ti
42、tration is electrometric, titrate toa well-defined inflection point at the voltage that correspondsto the voltage of the basic buffer solution, or (2) When titrationis colorimetric, add six drops of phenolphthalein indicatorsolution and titrate to the appearance of a permanent pinkcolor. Perform the
43、 blank titration on the water used to dissolvethe potassium acid phthalate. Calculate the molarity using thefollowing equation:Molarity 5Wp204.2331000V 2 Vb(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 t
44、itrate the salt to thespecific end point, mL, andVb= volume of titrant used to titrate the blank, mL.7.7.2 Phenolphthalein Indicator SolutionDissolve 0.10 gof solid pure phenolphthalein in 50 mL of water and 50 mL ofethyl alcohol.NOTE 7Commercially available reagents may be used in place of thelabor
45、atory preparations.NOTE 8Because of the relatively large coefficient of cubic expansionof organic liquids, such as isopropyl alcohol, the standard alcoholicsolutions should be standardized at temperatures close to those employedin the titrations of samples.7.8 Titration SolventPrepare by mixing tolu
46、ene, water,and anhydrous isopropyl alcohol in the ratio 100:1:99.8. 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 re
47、presentative sample causes serious errors.8.2 Heat the sample (Note 9) of used oil to 60 C 6 5Cinthe original container and agitate until all sediment is homo-geneously suspended in the oil (Note 10). If the originalcontainer is of opaque material, or if it is more than three-fourths full, transfer
48、the entire sample to a clear glass bottlehaving a capacity at least one third greater than the volume ofthe sample, and transfer all traces of sediment from the originalcontainer to the bottle by violent agitation of portions of thesample in the original container. After complete suspension ofall se
49、diment, strain the sample or a convenient aliquot througha 100-mesh screen for the removal of large contaminatingparticles (Note 9).NOTE 9When samples are visibly free of sediment, the heatingprocedure described in 8.2 may be omitted. When samples are visibly freeof sediment, the straining procedure may also be omitted.NOTE 10As used oil can change appreciably in storage, samplesshould be tested as soon as possible after removal from the lubricatingsystem and the dates of sampling and testing should be noted.9. Procedure for Acid Number9.1 Int
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