ASTM D974-2011 Standard Test Method for Acid and Base Number by Color-Indicator Titration《用颜色指示剂滴定法测定酸碱值的标准试验方法》.pdf

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1、Designation: D974 11Designation: 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 Department of Defense.1. Scope*1.1 This test method covers the determin

3、ation 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 bases w

4、hose 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, salts

5、of heavy metals, and addition agentssuch as inhibitors and detergents. Similarly, constituents considered tohave basic properties include organic and inorganic bases, amino com-pounds, salts of weak acids (soaps), basic salts of polyacidic bases, saltsof heavy metals, and addition agents such as inh

6、ibitors and detergents.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 c

7、onditions.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 known

8、.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 thi

9、s 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 value

10、s 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 safe

11、ty 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 Products

12、by 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 sp

13、ecified 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 po

14、int 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 Produc

15、ts and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of 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 approved May 15, 2011. Published

16、July 2011. Originallyapproved in 1948. Last previous edition approved in 2008 as D974081. DOI:10.1520/D0974-11.2Statements defining this test method, its modification, and its significance whenapplied to electrical insulating oils of mineral origin will be found in Guide D117.3For referenced ASTM st

17、andards, 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.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM In

18、ternational, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.sample in a specified solvent to a specified endpoint using aspecified detection system.3.1.2.1 DiscussionIn this test method, the indicator isp-naphtholbenzein titrated to an orange end point in a tolue

19、ne-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 quantity of base, ex-pressed in milligr

20、ams of potassium hydroxide per gram ofsample, that is required to titrate a hot water extract of thesample to a golden-brown end point using methyl orangesolution.4. Summary of Test Method4.1 To determine the acid or base number, the sample isdissolved in a mixture of toluene and isopropyl alcoholco

21、ntaining 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 (orange in acid and green-brown inbase)

22、. 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 contain basic oracidic constituen

23、ts 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, is a measure of thisamount of acid

24、ic 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 condemninglimits must be empirically es

25、tablished.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 number and the corrosive tendency

26、 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 subdivisions5-mL with 0.02-mL subdivision

27、sNOTE 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 otherwise indicated, it is intend

28、ed 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 high purity to permit its use withou

29、t 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).(WarningFlammable.)7.4 Hydrochloric A

30、cid Solution, Standard Alcoholic (0.1M)Mix 9 mLof concentrated hydrochloric acid (WarningCorrosive, fumes cause irritation) (HCl, sp gr 1.19) with 1000mL of anhydrous isopropyl alcohol (2-propanol) (WarningSee 7.3). Standardize frequently enough to detect molaritychanges of 0.0005 (Note 6), preferab

31、ly by electrometrictitration of approximately 8 mL (accurately measured) of the0.1 M alcoholic KOH solution diluted with 125 mL of carbondioxide-free water. When an electrometric titration is used forthe standardization, the end point shall be a well-definedinflection point closest to the cell volta

32、ge for the acidic buffersolution. When a colorimetric titration is used for the standard-ization, titrate to the first stable appearance of the orange colorwith methyl orange indicator.NOTE 5Commercially available reagents may be used in place of thelaboratory preparations when they are certified to

33、 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 Methyl Orange Indicator SolutionDisso

34、lve 0.1 g ofmethyl orange in 100 mL of water.7.6 p-Naphtholbenzein Indicator5,6SolutionThep-naphtholbenzein shall meet the specifications given inAnnexA1. Prepare a solution of p-naphtholbenzein in titration solventequal to 10 6 0.01 g/L.7.7 Potassium Hydroxide Solution, Standard Alcoholic (0.1M)Add

35、6gofsolid KOH (WarningHighly corrosive to allbody tissue) to approximately 1 L of anhydrous isopropylalcohol (containing less than 0.9 % water) in a 2-L Erlenmeyerflask. Boil the mixture gently for 10 to 15 min, stirring toprevent the solids from forming a cake on the bottom. Add atleast2gofbarium h

36、ydroxide (Ba(OH)2)(Warning4Reagent 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 th

37、e United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial 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 f

38、iled at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1626.D974 112Poisonous if ingested, strongly alkaline, causes severe irritationproducing dermatitis) and again boil gently for 5 to 10 min.Cool to room temperature, allow to stand for several hours, andfi

39、lter the supernatant liquid through a fine sintered-glass orporcelain filtering funnel; avoid unnecessary exposure tocarbon dioxide (CO2) during filtration. Store the solution in achemically resistant dispensing bottle out of contact with cork,rubber, or saponifiable stopcock lubricant and protected

40、 by aguard tube containing soda lime or soda nonfibrous silicateabsorbent (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 follows: Weigh, to the nearest 0.1 mgapproximately 0.

41、2 g of potassium acid phthalate, which hasbeen dried for at least1hat1106 1C and dissolve in 4061 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 point

42、at the voltage that corresponds tothe voltage of the basic buffer solution, or (2) When titration iscolorimetric, add six drops of phenolphthalein indicator solu-tion and titrate to the appearance of a permanent pink color.Perform the blank titration on the water used to dissolve thepotassium acid p

43、hthalate. Calculate the molarity using thefollowing equation:Molarity 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 titra

44、nt used to titrate the blank, mL.7.7.2 Prepare a 0.1 6 0.01 m% solution of phenolphthaleinby dissolving pure solid phenolphthalein in a 1:1 mixture ofwater, free of CO2, and ethanol.NOTE 7Commercially available reagents may be used in place of thelaboratory preparations.NOTE 8Because of the relative

45、ly 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 toluene, water,and anhydrous isopropyl alcohol in th

46、e 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 representative sample causes serious errors.8.2 He

47、at the sample (Note 9) of used oil to 60 6 5C in theoriginal container and agitate until all sediment is homoge-neously suspended in the oil (Note 10). If the original containeris of opaque material, or if it is more than three-fourths full,transfer the entire sample to a clear glass bottle having a

48、capacity at least one third greater than the volume of thesample, 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 sediment, strain the sample or a convenient aliquot

49、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 Into an appropriate size Erlenmeyer flask or a beaker,int