1、Designation: D 974 07Designation: 139/98An American National StandardStandard Test Method forAcid and Base Number by Color-Indicator Titration1This standard is issued under the fixed designation D 974; 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 (e) 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
3、 test method covers the determination 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;
4、 extremely weak acids or bases 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, phenoliccom
5、pounds, lactones, resins, salts 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,
6、 and addition agents such as inhibitors and detergents.NOTE 2This test method is not suitable for measuring the basicconstituents of many basic additive-type lubricating oils. Test MethodD 4739 can be used for this purpose.1.2 This test method can be used to indicate relative changesthat occur in an
7、 oil during use under oxidizing 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
8、and acid or base numbers is known.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 byTest Method D 664
9、.The acidnumbers obtained by this color-indicator test method need not benumerically the same as those obtained by Test Method D 664, the basenumbers obtained by this color indicator test method need not benumerically the same as those obtained by Test Method D 4739, but theyare generally of the sam
10、e order of magnitude.1.3 The values 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 stand
11、ard to establish appro-priate safety 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 Specifica-tions for Electrical Insulating Oils of Petroleum OriginD 664 Test Method
12、forAcid Number of Petroleum Productsby Potentiometric TitrationD 1193 Specification for Reagent WaterD 4175 Terminology Relating to Petroleum, PetroleumProducts, and LubricantsD 4739 Test Method for Base Number Determination byPotentiometric Titration3. Terminology3.1 Definitions:3.1.1 acid number,
13、nthe quantity of base, expressed inmilligrams of potassium hydroxide per gram of sample that isrequired to titrate a sample to a specified end point.3.1.1.1 DiscussionIn this test method, the indicator isp-naphtholbenzein titrated to a green/green-brown end point ina toluene-water-isopropanol solven
14、t.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products 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
15、 as a joint ASTM-IP standard in 1965.Current edition approved Nov. 1, 2007. Published November 2007. Originallyapproved in 1948. Last previous edition approved in 2006 as D 97406.2Statements defining this test method, its modification, and its significance whenapplied to electrical insulating oils o
16、f mineral origin will be found 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.1*A Summary of C
17、hanges 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.3.1.2 base number, nthe quantity of acid, expressed inmilligrams of potassium hydroxide per gram of sample that isrequired to titrate a
18、 sample to a specified end point.3.1.2.1 DiscussionIn this test method, the indicator isp-naphtholbenzein titrated 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) whe
19、ther operated or not. D 41753.2 Definitions of Terms Specific to This Standard:3.2.1 strong acid number, nthe quantity of base, ex-pressed in milligrams 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 ora
20、ngesolution.4. Summary of Test Method4.1 To determine the acid or base number, the sample isdissolved in a mixture 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
21、 solution, respectively, to theend point indicated by the color change of the addedp-naphtholbenzein solution (orange 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 hy
22、droxide solution, usingmethyl orange as an indicator.5. Significance and Use5.1 New and used petroleum products can 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
23、 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 acidic or basic substances, respectively, in theoilalways under the conditions of the test. This number isused as a guide in the quality control of lubrica
24、ting oilformulations. It is also sometimes used as a measure oflubricant degradation in service; however, any condemninglimits 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 can
25、not be used to predict corrosiveness ofan oil under service conditions. No general correlation isknown between acid 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 fo
26、llowing 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 subdivisionsNOTE 4An automated buret capable of delivering titrant amounts in0.05-mL or smaller increments can be used but the stated precision datawere obtained
27、using manual burets only.7. Reagents7.1 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 Chemical Society,where such specificat
28、ions are available.4Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high 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 requireme
29、nts ofeither Type I, II, or III of Specification D 1193.7.3 Isopropyl Alcohol, anhydrous (less than 0.9 % water).(WarningFlammable.)7.4 Hydrochloric Acid Solution, Standard Alcoholic (0.1M)Mix 9 mLof concentrated hydrochloric acid (WarningCorrosive, fumes cause irritation) (HCl, sp gr 1.19) with 100
30、0mL of anhydrous isopropyl alcohol (2-propanol) (WarningSee 7.3). Standardize frequently enough to detect molaritychanges of 0.0005 (Note 6), preferably by electrometrictitration of approximately 8 mL (accurately measured) of the0.1 M alcoholic KOH solution diluted with 125 mL of carbondioxide-free
31、water. When an electrometric titration is used forthe standardization, the end point shall be a well-definedinflection point closest to the cell voltage for the acidic buffersolution. When a colorimetric titration is used for the standard-ization, titrate to the first stable appearance of the orange
32、 colorwith methyl orange indicator.NOTE 5Commercially available reagents may be used in place of thelaboratory preparations 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
33、 mg ofKOH. Sodium hydroxide (NaOH) and sulfuric acid (H2SO4) can besubstituted for KOH and HCl, respectively.7.5 Methyl 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 inAnne
34、xA1. 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)Add6gofsolid KOH (WarningHighly corrosive to allbody tissue) to approximately 1 L of anhydrous isopropylalcohol (containing less than 0.9 % water) in a 2
35、-L Erlenmeyerflask. Boil the mixture gently for 10 to 15 min, stirring toprevent the solids from forming a cake on the bottom. Add atleast2gofbarium hydroxide (Ba(OH)2)(Warning4Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on t
36、he testing of 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.5In a 2006 study, only Kodak, Baker (Mall
37、inkrodt), 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 requesting Research Report RR:D021626.D974072Poisonous if ingested, strongly alkaline, c
38、auses severe irritationproducing dermatitis) and again boil gently for 5 to 10 min.Cool to room temperature, allow to stand for several hours, andfilter the supernatant liquid through a fine sintered-glass orporcelain filtering funnel; avoid unnecessary exposure tocarbon dioxide (CO2) during filtrat
39、ion. Store the solution in achemically resistant dispensing bottle out of contact with cork,rubber, or saponifiable stopcock lubricant and protected by aguard tube containing soda lime or soda nonfibrous silicateabsorbent (Ascarite, Carbosorb, or Indecarb).7.7.1 Standardization of Potassium Hydroxid
40、e SolutionStandardize frequently enough to detect changes of 0.0005 N.One way to do this is as follows: Weigh, to the nearest 0.1 mgapproximately 0.2 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 potassiumhy
41、droxide alcoholic solution to either of the following endpoints: (1) When the titration is electrometric, titrate to awell-defined inflection point at the voltage that corresponds tothe voltage of the basic buffer solution, or (2) When titration iscolorimetric, add six drops of phenolphthalein indic
42、ator solu-tion and titrate to the appearance of a permanent pink color.Perform the blank titration on the water used to dissolve thepotassium acid phthalate. Calculate the normality using thefollowing equation:Normality 5Wp204.2331000V2Vb(1)where:Wp= weight of the potassium acid phthalate, g,204.23
43、= molecular weight of the potassium acid phthalate,V = volume of titrant used to titrate the salt to thespecific end point, mL, andVb= volume of titrant 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 of
44、water, free of CO2, and ethanol.NOTE 7Commercially available reagents may be used in place of thelaboratory preparations.NOTE 8Because of the relatively large coefficient of cubic expansionof organic liquids, such as isopropyl alcohol, the standard alcoholicsolutions should be standardized at temper
45、atures close to those employedin the titrations of samples.7.8 Titration SolventPrepare by mixing toluene, 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 it
46、self 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 suspended in the oil (Note 10)
47、. 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 acapacity at least one third greater than the volume of thesample, and transfer all traces of sediment from the originalcontainer to the bottle by viol
48、ent agitation of portions of thesample in the original container. After complete suspension ofall sediment, 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 heatingprocedur
49、e 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,introduce a weighed quantity of the sample as given in Table 1.Add 100 mLof the titration solvent and 0.5 mLof the indicatorsolution, and without stopperin
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