1、Designation: D5770 11Standard Test Method forSemiquantitative Micro Determination of Acid Number ofLubricating Oils During Oxidation Testing1This standard is issued under the fixed designation D5770; the number immediately following the designation indicates the year oforiginal adoption or, in the c
2、ase 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 is a semiquantitative micro methodintended for monitoring the changes i
3、n acidic constituentsoccurring in lubricating oils during oxidation testing, when theacid number of such oils falls within the range from 0.02 to 1.0mg of potassium hydroxide per gram of sample. It is applicableto such oils as turbine oils, hydraulic oils, and other circulatingoils.NOTE 1This test m
4、ethod is a micro version of Test Method D974 andit produces results similar to that method.1.2 This test method is designed for use where sample sizeis limited. It shall not be used as a replacement for higherprecision methods such as Test Methods D974 or D664. It shallnot be used to monitor oils in
5、-service.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.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 esta
6、blish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D664 Test Method for Acid Number of Petroleum Productsby Potentiometric TitrationD943 Test Method for Oxidation Characteristics of Inhib-i
7、ted Mineral OilsD974 Test Method for Acid and Base Number by Color-Indicator TitrationD3339 Test Method for Acid Number of Petroleum Prod-ucts by Semi-Micro Color Indicator TitrationD4871 Guide for Universal Oxidation/Thermal StabilityTest Apparatus3. Terminology3.1 Definitions:3.1.1 acid number, nt
8、he quantity of a 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 acid number iscalculated from the number of drops
9、 required to produce achange in solution color from blue-green to orange, comparedto the number of drops required to produce an identical colorchange using a reference standard. Because this is a directcomparison method, the acid number value can be reported inmilligrams of potassium hydroxide per g
10、ram of sample.4. Summary of Test Method4.1 A 2.0-mL portion of the titration solution is titrated witha sample using a dropping pipet. The number of drops ofsample required to turn the blue-green titration solution to apersistent orange color is noted.4.2 A second 2.0-mL portion of the titration sol
11、ution istitrated with an acid number reference solution of known acidnumber. The number of drops of the reference solutionrequired to turn the blue-green titration solution to a persistentorange color is noted.4.3 The estimated acid number of the sample is calculatedusing the acid number of the refe
12、rence solution and the ratio ofthe number of drops of the reference solution required to effectthe color change to the number of drops of the sample requiredfor the same change.5. Significance and Use5.1 This test method provides a semiquantitative estimate ofthe acid number of lubricating oils obta
13、ined from laboratoryoxidation tests using smaller amounts of sample than TestMethods D974, D664,orD3339. It has specific application inTest Method D943 and in Test Method D4871. This testmethod, therefore, provides a means of monitoring the relative1This test method is under the jurisdiction of ASTM
14、 Committee D02 onPetroleum Products and Lubricants and is the direct responsibility of SubcommitteeD02.06 on Analysis of Lubricants.Current edition approved May 15, 2011. Published July 2011. Originallyapproved in 1995. Last previous edition approved in 2007 as D577002(2007).DOI: 10.1520/D5770-11.2F
15、or 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 Changes section appears at the end of this stand
16、ard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.oxidation of lubricating oils by measuring changes in acidnumber, at different time intervals and under various oxidizingtest conditions.5.2 Since this test method is semiquantitativ
17、e, each labora-tory shall develop its own criteria for each oxidation testmethod for determining when to switch from this semiquanti-tative test method to a more precise test method for acidnumber.6. Apparatus6.1 Glass Beakers, 10-mL capacity, or glass vials, 4 or 6dram.6.2 Glass Syringe, 2-5 mLcapa
18、city.A5-mLinterchangeablesyringe with a 20 gage, 12 cm needle is satisfactory.6.3 Dropping Pipet, glass with rubber bulb, capable ofdelivering 35 to 40 drops of oil.7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests. Unless indicated otherwise, it is intended thatall
19、reagents shall conform to the specifications of the Commit-tee on Analytical Reagents of the American Chemical Society,where such specifications are available.3Other grades can beused provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening
20、theaccuracy of the determination.7.2 Acid Number Reference SolutionAny stable, oil-soluble acid which will produce an acid number of approxi-mately 0.5 mg KOH/g is acceptable. This solution shall bestandardized using Test Method D974 or D664. A solution of0.20 % mass dodecenylsuccinic anhydride in H
21、VI 250 base oilor in an ISO 10-22 (60-100 SUS) oil has proven satisfactory.7.3 Alcoholic Potassium Hydroxide Standard Solution (0.1M)Prepare approximately 0.1 M solution by dissolving KOHin propanol-2-ol. Standardize against pure potassium acidphthalate in about 100 mL of water, using phenolphthalei
22、n todetect the end point. (Commercial grades of this reagent havebeen found to be satisfactory.) (WarningCorrosive.)(WarningPoisonous if ingested, alkaline, causes irritationproducing dermatitis.)7.4 Dodecylsuccinic Anhydride(WarningIrritating toeyes and skin.)7.5 p-Naphtholbenzein Indicator Solutio
23、nThep-naphtholbenzein must meet the specifications in AppendixX1 of Test Method D974. Prepare a solution containing 10 g ofp-naphtholbenzein/L in a 50:50 mixture of toluene:propanol-2-ol. (WarningFlammable. Vapor harmful.)NOTE 2In a 1992 study, only Kodak, Fisher, and Baker (Mallinkrot)were found to
24、 meet the specifications. However, the Kodak brand is nolonger available. The Fisher Reagent Solution was the only commerciallyavailable solution to meet the specifications.7.6 Propanol-2-ol (Isopropyl Alcohol)(WarningFlammable.) (WarningIt has been reported that, unlessinhibited against it, peroxid
25、es can form in propanol-2-ol and, asthe storage vessel or equipment such as a dispensing bottlebecome empty and approach dryness, an explosive mixture canoccur.)7.7 Titration SolutionMix 350 mL of toluene, 350 mL ofpropanol-2-ol, and 7 mL of the p-naphtholbenzein solution ina 1-L plastic bottle. Add
26、 15 mL of 0.1 M potassium hydroxidealcoholic solution and mix well. (WarningFlammable. Va-por harmful. Corrosive.)NOTE 3The strength of the titration solution depletes with time andshould be periodically replaced. Up to one month has been found to besatisfactory.7.8 Toluene(WarningFlammable. Vapor h
27、armful.)8. Procedure8.1 SamplingWithdraw the minimal amount of the test oilfrom the oxidation test cell according to the procedure speci-fied in the oxidation test method.NOTE 4As oxidized oils can change appreciably in storage, samplesshould be tested as soon as possible after removal from the oxid
28、ation testequipment.8.2 Using the syringe, measure 2.0 mL of the titrationsolution into a 10-mL beaker or vial.8.3 Using the dropping pipet, add the oil sample to thetitration solution one drop at a time, swirling constantly.8.4 Count the number of drops of oil sample required tochange the titration
29、 solution color from blue-green to orange.Consider the titration complete when the orange color is stablefor a minimum of 10 s.8.5 Repeat 8.2 through 8.4 using the acid number referencesolution in place of the oil sample as the titrant of 2.0 mL oftitration solution, so that the final colors for the
30、 two beakersmatch.9. Calculation and Report9.1 Calculate the acid number of the oil sample as follows:acid number, mg KOH/g 5A 3 BC(1)where:A = number of drops of the acid number reference solutionin 8.5,B = acid number of the acid number reference solution, andC = number of drops of the oil sample
31、(8.4).9.2 Report the result as follows:acid number, Test Method D 5770! 5 result! (2)10. Precision and Bias10.1 PrecisionThe precision of this test method wasdetermined by statistical examination of interlaboratory testresults over the acid number range from 0.06 to 1.1 mg KOH/gfor nine samples anal
32、yzed by eight laboratories.43Reagent Chemicals, American Chemical Society Specifications , AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and
33、 the United States Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.4Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR:D02-1356.D5770 11210.1.1 RepeatabilityThe difference between two tes
34、t re-sults, obtained by the same operator with the same apparatusunder constant operating conditions on identical test material,would in the long run, in the normal and correct operation ofthe test method, exceed the following values only in one casein twenty:0.20 3 acid number (3)10.1.2 Reproducibi
35、lityThe difference between two singleand independent results, obtained by different operators work-ing in different laboratories on identical test material, would inthe long run, in the normal and correct operation of the testmethod, exceed the following values only in one case intwenty:0.70 3 acid
36、number (4)10.2 BiasThe procedures in this test method have no biasbecause the acid number can be defined only in terms of thetest method.11. Keywords11.1 acid number; color indicator titration; oxidation test-ing; semiquantitativeSUMMARY OF CHANGESSubcommittee D02.06 has identified the location of s
37、elected changes to this standard since the last issue(D577002(2007) that may impact the use of this standard.(1) Updated 3.1.1.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are
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