ASTM D8126-2017 7500 Standard Test Method for Efficient Basicity Determination by Potentiometric Hydrochloric Acid Titration《电位滴定法测定高效碱度的标准试验方法》.pdf

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1、Designation: D8126 17Standard Test Method forEfficient Basicity Determination by PotentiometricHydrochloric Acid Titration1This standard is issued under the fixed designation D8126; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, t

2、he 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. Scope1.1 This test method covers a procedure for the determina-tion of the efficient basicity (EBas) in new marine c

3、ylinderlubricants that lubricate the upper part, that is, piston-ring-cylinder area, of two-stroke marine engines.1.2 This test method has been developed for marine cylinderlubricants, having base number (BN) (measured by TestMethod D2896) from 20 mg KOH/g to 100 mg KOHg, and anEBas from 10 mg KOH/g

4、 to 36 mg KOH/g.1.3 In this test method, only the efficient basicity isdetermined, corresponding to the components or part of com-ponents that have a major role in neutralization of the acidicspecies formed in the combustion of the fuel in the marineengine. It differentiates between the fastest reac

5、ting species andthe last one to react like overbasing compounds in detergent(classically mineral calcium carbonate, CaCO3). The valuesobtained, however, are intended to be compared with the othervalues obtained by this test method only; base numbersobtained by this test method are not intended to be

6、 equal tovalues by other test methods.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the u

7、ser of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Some specifichazards statements are given in Sections 6 and 7.1.6 This international standard was developed in accor-dance with internationally recogniz

8、ed principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for

9、Reagent WaterD2896 Test Method for Base Number of Petroleum Productsby Potentiometric Perchloric Acid TitrationD4739 Test Method for Base Number Determination byPotentiometric Hydrochloric Acid TitrationD6300 Practice for Determination of Precision and BiasData for Use in Test Methods for Petroleum

10、Products andLubricants3. Terminology3.1 Definitions:3.1.1 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 asample in a specified solvent to a specified endpoint using aspecified det

11、ection system.3.1.2 effcient basicity, EBas, nthe quantity of hydrochlo-ric acid, expressed in terms of the equivalent number ofmilligrams of potassium hydroxide per gram of sample, re-quired to neutralize the basic components, which are organicspecies, of the tested lubricant in a specified solvent

12、 to aspecified buffer endpoint using a specified detection system.4. Summary of Test Method4.1 The sample is dissolved in a mixture of toluene,propan-2-ol (isopropyl alcohol), chloroform, and a smallamount of water and titrated potentiometrically with alcoholichydrochloric acid solution. The test re

13、sults of this procedureare obtained by titration mode of fixed increment and fixedtime additions of the titrant. An endpoint is selected from atitration curve according to the criteria given in Section 12 andused to calculate the EBas.5. Significance and Use5.1 Lubricants can contain basic constitue

14、nts that are pres-ent as additives. The relative amount of these materials can be1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility ofSubcommittee D02.06 on Analysis of Liquid Fuels and Lubricants.Curr

15、ent edition approved July 1, 2017. Published September 2017. DOI:10.1520/D8126-17.2For 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 pag

16、e onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for th

17、eDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1determined by titration with acids. The base number is ameasurement of the amount of basic substances in the oil underthe conditions of the testing

18、procedure.5.2 Aprimary objective of a marine cylinder lubricant is theneutralization of sulfuric acid, produced during fuelcombustion, to protect the engine from corrosion. The EBasmethod characterizes the more efficient basic species of thelubricant reacting with acids from the beginning of the neu

19、-tralization (when the lubricant milieu is basic) until an equi-librium state where the lubricant becomes slightly acidic. Theuse of hydrochloric acid (HCl) allows differentiating basicitiesof various strengths during titration.5.3 In marine lubricants, the constituents that can be con-sidered to ha

20、ve basic properties are primarily organic andinorganic bases coming from the detergent. Basicity can alsobe brought to the lubricant by other components includingdispersants, amino compounds, or any organic basic compo-nents. This test method uses the same titration system as that ofTest Method D473

21、9, however the evaluation and interpretationof the titration result is different. The hydrochloric acid is usedas the titrant in this test method and Test Method D4739,whereas Test Method D2896 uses a stronger acid, perchloricacid. While all three methods can be considered as comple-mentary to evalu

22、ate the basicity of lubricants, this test methodis only used for marine cylinder lubricants.5.4 This test method measures only the efficient basicity ofthe lubricant, which represents only the part of the totalbasicity, until the point of which the lubricant becomes slightlyacidic. It will depend on

23、 the components of the formulationitself. In that respect, the EBas cannot be compared to basenumber given by Test Methods D4739 or D2896. The EBas isthen complementary information to the base number, givingperformance in efficiency of neutralization of acidic species.6. Apparatus6.1 Potentiometric

24、Titration, automatic or manual, withcapability of adding fixed increments of titrant at fixed timeintervals (see Annex A1).6.1.1 The titrimeter must automatically (or manually) con-trol the rate of addition of titrant as follows: Delivery of titrantwill be incremental; after delivery of precisely a

25、0.100 mLincrement (see 6.1.2), the delivery is stopped and a fixed timeperiod of 90 s is allowed to pass before another 0.100 mLincrement of titrant is delivered. This procedure is repeateduntil the titration is completed.6.1.2 The precision of addition of the 0.100 mL incrementsof titrant must be 6

26、0.001 mL for automatic titrators. Formanual buret, it should be 60.005 mL. A higher incrementalprecision is required for an automatic buret, because the totalvolume to the end point is summed from the individualincrements; it is read from a scale with a manual buret.6.2 Sensing Electrode, standard p

27、H with glass membrane,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 Mlithium chloride (LiCl) in ethanol.6.3.1 Combination ElectrodeSensing electrodes may havethe silver/silver chloride (Ag/A

28、gCl) reference electrode builtinto the same electrode body, which offers the convenience ofworking with and maintaining only one electrode. The combi-nation electrode shall have a sleeve junction type of referenceand shall use an inert ethanol electrolyte, for example, 1 M to3 M LiCl in ethanol.6.3.

29、1.1 In the reference compartment, the sensing electrodepart shall use a glass membrane designed for nonaqueoustitrations. These combination electrodes shall have the sameresponse or better response than a dual electrode system. Theyshall have removable sleeves for easy rinsing and addition ofelectro

30、lyte. When a movable sleeve is part of the electrodesystem, ensure that the sleeve is unimpaired before everytitration.6.4 Stirrer, Buret, Stand, Titration Vessel, as specified inAnnex A1, are required.7. Reagents7.1 Purity of ReagentsReagent-grade chemicals shall beused in all tests. Unless otherwi

31、se 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.3Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purit

32、y to permit its use without lessening theaccuracy of the determination.7.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water that meetsthe requirement of either Type I, II, or III of SpecificationD1193.7.3 Buffer, Aqueous AcidCommercial pH 5 buff

33、er solutionwith a tolerance of 60.02 pH units at 25 C. This solution shallbe replaced at regular intervals consistent with its stability orwhen contamination is suspected. Information related to thestability should be obtained from the manufacturer.7.4 ChloroformReagent grade. (WarningToxic andsuspe

34、cted carcinogen.)7.5 Hydrochloric Acid Solution, Standard Alcoholic (0.1M)Mix 9 mL of reagent grade hydrochloric acid (HCl, sp gr1.19) (WarningToxic and corrosive), with 1 L of anhydrousisopropyl alcohol. Standardize frequently enough to detectnormality changes of 0.0005 by potentiometric titration.

35、 ofapproximately 0.1 g (weigh accurately at the nearest 0.0001 g)of primary standard Tris(hydroxymethyl)aminomethane dis-solved in 60 mL CO2-free water.7.6 Ethanolreagent grade. (WarningFlammable andtoxic, especially when denatured.)7.7 Lithium Chloride ElectrolytePrepare a solution of 1 Mto 3 M LiC

36、l in ethanol.3Reagent 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 the United Stat

37、es Pharmacopeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D8126 1727.8 Propan-2-ol (Isopropyl Alcohol)Anhydrous, (less than0.1 % H2O). (WarningFlammable.)7.9 Commercially available solutions may be used in placeof laboratory preparations provided the solutions h

38、ave beencertified as equivalent.7.10 Alternative volumes of solutions may be preparedprovided the final solution concentration is equivalent.7.11 TolueneReagent grade. (WarningExtremely flam-mable.)7.12 Titration SolventIn a brown reagent bottle, add30 mL of water to 1 L of isopropyl alcohol, and mi

39、x thor-oughly. Add 1 L each of toluene and chloroform, and mixthoroughly.7.13 Tris(hydroxymethyl)aminomethane (HOCH2)3CNH2),primary standard, driedCrush a 1 g to 3 g portion of primarystandard Tris(hydroxymethyl)aminomethane to a fine powderusing an agate or other nonreactive mortar and pestle for 6

40、0 sto 90 s. Take special care to crush any larger crystals. Dry thecrushed material at room temperature (22 C to 23 C) for 24 hin a vacuum desiccator over anhydrous magnesium perchlorateor equivalent. Drying of this material at elevated temperaturesis not recommended, owing to the possibility of dec

41、omposi-tion.8. Preparation of Electrode System8.1 Maintenance and Storage of ElectrodesCleaning theelectrode thoroughly, keeping the ground-glass joint free offoreign materials, and regular testing of the electrodes are veryimportant in obtaining repeatable potentials, since the contami-nation may i

42、ntroduce uncertain erratic and unnoticeable liquidcontact potentials. While this is of secondary importance whenend points are chosen from inflection points in the titrationcurve, it may be very serious when end points are chosen atexperimentally determined cell potentials as outlined in theprocedur

43、e.8.1.1 Clean the pH indicating electrode or the pH indicatingpart of the combination electrode at frequent intervals based onuse and type of samples being analyzed by immersing innon-chromium containing, strongly oxidizing cleaning solu-tion.8.1.1.1 The electrode shall be cleaned periodically when

44、inuse or when a new electrode is installed. Drain the LiClelectrolyte from the electrode at least once each week, andrefill with fresh LiCl electrolyte as far as the filling hole.Ensure that there are no air bubbles in the electrode liquid. Ifair bubbles are observed, hold the electrode in a vertica

45、lposition and gently tap it to release the bubbles. Maintain theelectrolyte level in the electrode above that of the liquid in thetitration beaker at all times.8.1.2 When not in use, immerse the lower halves of theelectrodes in either water (sensing) or the LiCl in isopropylalcohol electrolyte (refe

46、rence). Do not allow them to remainimmersed in titration solvent for any appreciable period of timebetween titrations. While the electrodes are not extremelyfragile, handle them carefully at all times.8.1.3 Electrode LifeTypically, electrode usage is limitedto 3 months to 6 months, depending upon us

47、age. Electrodeshave a limited shelf life and shall be tested before use (8.3).8.2 Preparation of Electrodes:8.2.1 When Ag/AgCl reference electrode is used for thetitration and it contains an electrolyte that is not 1 M to 3 MLiCl in ethanol, replace the electrolyte. Drain the electrolytefrom the ele

48、ctrode, wash away all the salt (if present) withwater and then rinse with ethanol. Rinse several times with theLiCl electrolyte solution. Finally, replace the sleeve and fill theelectrode with the LiCl electrolyte to the filling hole. Whenrefitting the sleeve, ensure that there will be a free flow o

49、felectrolyte into the system. A combination electrode shall beprepared in the same manner. The electrolyte in a combinationelectrode can be removed with the aid of a vacuum suction.8.2.2 Prior to each titration, soak the prepared electrodes inwater, pH 4.5 5.5 acidified with HCl, for at least 5 min. Rinsethe electrode with propan-2-ol immediately before use, andthen with the titration solvent.8.3 Testing of ElectrodesSee Appendix X2 for the proce-dure to check electrode performance.9. Standardization of Apparatus9.1 Prepare the electrodes as described in