1、Designation: D 1287 91 (Reapproved 2002)Standard Test Method forpH of Engine Coolants and Antirusts1This standard is issued under the fixed designation D 1287; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revisi
2、on. 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. Scope1.1 This test method covers the determination of th
3、e pH ofunused engine coolants and antirusts, and used or unusedaqueous dilutions of the concentrated products.NOTE 1Antirusts in solid form are not included in this test method.NOTE 2It is believed that this procedure gives all the informationrequired for determining the pH of samples of engine cool
4、ant or antirustlikely to be encountered. Should additional information on pH determi-nations be needed, reference should be made to Test Method E 70.1.2 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 s
5、tandard 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:D 1176 Practice for Sampling and Preparing Aqueous So-lutions of Engine Coolants or Antirusts for Testing Pur-poses2E 70 Tes
6、t Method for pH of Aqueous Solutions with theGlass Electrode23. Summary of Test Method3.1 A sample, as received or after dilution with a specifiedvolume of distilled water, is placed in a beaker or sample cupand the pH measured with a pH meter and associated glass-saturated calomel electrode pair.NO
7、TE 3The readings of the meter in the case of the concentratedproducts are not pH values according to the accepted definition, but areapparent pH values which are useful in the interpretation of the conditionof the product.4. Significance and Use4.1 pH is a measure of the hydrogen ion concentration a
8、ndindicates whether an engine coolant, antirust, or a solution ofthese compounds is acidic, alkaline, or neutral.4.2 pH is sometimes used for production quality control. Itis generally desirable that engine coolants have an alkaline pH.4.3 pH is not significant from the standpoint of predictingservi
9、ce life. The pH of used engine coolants or antirustsolutions is not a dependable indication of either existingeffectiveness or remaining life of the solution.5. Apparatus5.1 The pH meter, glass electrode, and calomel electrode,shall be as specified in the Annex.6. Reagents6.1 Purity of ReagentsReage
10、nt 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 specifications are available.3Other grades may beused, provided it is fir
11、st ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of the determination.6.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean distilled water or water ofequal purity. Distilled water shall be boiled th
12、oroughly, orpurged with carbon dioxide-free air, to remove carbon dioxideand shall be protected with a soda-lime tube or its equivalentwhile cooling and in storage. The pH of the water shall bebetween 6.2 and 7.2 at 25C.6.3 Standard Buffer SolutionsThe buffer solutions forcalibrating the pH meter an
13、d electrode pair shall be preparedfrom salts sold specifically for use, either singly or in combi-nation, as pH standards. The salts shall be dried for1hat110C before use, except in the case of borax which shall beused as the decahydrate. The solutions with pH less than 9.5shall be stored in chemica
14、lly resistant bottles. The alkalinephosphate solution shall be stored in glass bottles coated on theside with paraffin.1This test method is under the jurisdiction of ASTM Committee D15 on EngineCoolants and is the direct responsibility of Subcommittee D15.04 on ChemicalProperties.Current edition app
15、roved June 15, 1991. Published October 1991. Originallypublished as D 1287 53 T. Last previous edition D 1287 85.2Annual Book of ASTM Standards, Vol 15.05.3Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagent
16、s 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. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box
17、C700, West Conshohocken, PA 19428-2959, United States.NOTE 4Commercially available buffer tablets or prepared buffersolutions may be used.6.4 Potassium Hydrogen Phthalate Buffer Solution (0.05M, pH = 4.01 at 25C)Dissolve 10.21 g of potassiumhydrogen phthalate (KHC8H4O4) in water, and dilute to 1 L.6
18、.5 Neutral Phosphate Buffer Solution (0.025 M with re-spect to each phosphate salt, pH = 6.86 at 25C)Dissolve3.40 g of potassium dihydrogen phosphate (KH2PO4) and 3.55g of anhydrous disodium hydrogen phosphate (Na2HPO4)inwater and dilute to 1 L.6.6 Borax Buffer Solution (0.01 M, pH = 9.18 at 25C)Dis
19、solve 3.81 g of disodium tetraborate decahydrate (Na2B4O710H2O) in water, and dilute to 1 L. Protect this solution fromatmospheric carbon dioxide; stopper the bottle at all timesexcept when actually in use.6.7 Alkaline Phosphate Buffer Solution (0.01 M trisodiumphosphate, pH = 11.72 at 25C)Dissolve
20、1.42 g of anhy-drous disodium hydrogen phosphate (Na2HPO4) in 100 mL ofa 0.1 M carbonate-free solution of sodium hydroxide and diluteto 1 L with water.6.8 Potassium Chloride ElectrolytePrepare a saturatedsolution of potassium chloride (KCl) in water.7. Sampling7.1 Sample material in accordance with
21、Practice D 1176.8. Preparation of Electrode System8.1 Maintenance of ElectrodesClean the glass electrode atfrequent intervals (not less than once every week duringcontinual use) in accordance with the manufacturers instruc-tions. Drain the calomel electrode at least once each week andfill with KCl e
22、lectrolyte. Keep the electrolyte level in thecalomel electrode above that of the solution being tested at alltimes. When not in use, immerse the lower halves of theelectrodes in distilled water, or the appropriate buffer solutionrecommended by the manufacturer. Do not immerse theelectrodes in the so
23、lution being tested for any appreciableperiod of time between determinations. Although the elec-trodes are not extremely fragile, they should be handledcarefully at all times.8.2 Preparation of ElectrodesBefore and after using,wipe the electrode thoroughly with a clean cloth, or a softabsorbent tiss
24、ue, and rinse with distilled water. Follow themanufacturers recommendations if further preparation is re-quired. Prior to each pH determination, soak the preparedelectrode in distilled water for at least 2 min. Immediatelybefore use, touch the tips of the electrodes with a dry cloth ortissue to remo
25、ve excess water.9. Standardization and Testing of Electrode System inpH Units9.1 The assembly shall always be standardized with one ofthe standard buffer solutions. A second standard buffer solutionshall be used to check the linearity of the response of theelectrodes at different pH values and to de
26、tect a faulty glasselectrode or incorrect temperature compensation. The twobuffer solutions selected should bracket the anticipated pH ofthe solutions being tested.9.1.1 Turn on the instrument, allow it to warm up, andadjust according to the manufacturers instructions. Immersethe tips of the electro
27、des in the standard buffer solution chosenand allow sufficient time for the temperature of the buffersolution and the electrodes to equalize. Set the temperatureknob at the temperature of the buffer solution. Adjust thestandardization or asymmetry potential control until the meterregisters a scale r
28、eading, in pH units, equal to the known pH ofthe standardizing buffer solution.9.1.2 Rinse the electrodes with distilled water and touch thetips with a dry cloth or tissue to remove excess water. Immersethe electrodes in a second standard buffer solution. The readingof the meter shall agree with the
29、 known pH of the secondstandard buffer solution within 60.05 unit without changingthe setting of the standardization of asymmetry potentialcontrol. If it does not agree or if the meter gives a slowresponse time and drifts, the electrode should be cleaned inaccordance with the manufacturers instructi
30、ons.9.1.3 The presence of a faulty electrode is indicated byfailure to obtain a correct value for the pH of the secondstandard buffer solution after the meter has been standardizedwith the first. A cracked electrode will often yield pH valuesthat are essentially the same for both standard buffer sol
31、utions.10. Procedure10.1 Make the pH determination on (1) the unused concen-trated engine coolant or antirust (as received), or (2) anydesired dilution, with distilled water, of the concentratedproduct, or (3) used engine coolant or antirust solution. Fordilute solutions, suggested engine coolant co
32、ncentrations are50 and 33 volume %; antirust solution concentration should bein the range of proposed usage. Prepare solutions as follows:Unused engine coolant or antirust solution samples to be testedshould be obtained following the applicable portions of theprocedure outlined in Practice D 1176.10
33、.1.1 When a small, insoluble liquid layer is present,remove it prior to testing the unused sample or preparingdiluted samples for testing. Using a 100-mL mixing cylinderand a pipet or other suitable measuring device, make up asolution of the concentration desired for testing by measuringthe necessar
34、y amount of antifreeze or antirust solution into thecylinder and adding sufficient distilled water to bring thesolution volume to 100 mL.10.1.2 Thoroughly mix the contents of the cylinder byshaking, and transfer into a 250-mL tall-form spoutless or othersuitable beaker.NOTE 5Some pH apparatus is equ
35、ipped with a sample cup. It issatisfactory to use these cups and the smaller sample required with them,as an alternative to the 100-mL sample and beaker specified.10.2 Prepare the calomel and glass electrodes as directed inSection 8. Immerse the tip of the electrode in the solution andagitate. Where
36、 the instrument has a mechanical stirrer, this maybe used. Allow the system to come to equilibrium, and recordthe pH value. Remove and wash the electrodes with distilledwater and immerse them in distilled water until the nextdetermination is made.NOTE 6In the event that the glass electrodes become c
37、oated with anoil film, as the result of testing two-phase products, it is necessary toD 1287 91 (2002)2remove such film with a suitable solvent, such as 1 + 1 mixture of tolueneand ethyl acetate.NOTE 7With silicate-containing engine coolant, it is important tospecify that the pH reading be taken eit
38、her immediately after preparing thedilution or after a specified period of time, such as 30 min. In contrast toan immediate pH, the 30-min value has been shown to be approximately0.2 units lower and a measurement made after 24 h can be from 0.3 to 0.5pH units lower.11. Report11.1 Report the pH.12. P
39、recision and Bias12.1 RepeatabilityDuplicate results by the same operatorshould not be considered suspect unless they differ by morethan 60.1 pH units.12.2 ReproducibilityThe results submitted by two or morelaboratories should not be considered suspect unless the resultsdiffer by more than 60.2 pH u
40、nits.13. Keywords13.1 antirusts; engine coolants; pH of engine coolantsANNEX(Mandatory Information)A1. APPARATUSA1.1 MeterA1.1.1 A voltmeter or potentiometer that will operate withan accuracy of 60.005 V and a sensitivity of 60.002 V, overa range of at least 60.5 V, when the meter is used with theel
41、ectrodes specified in A1.2 and A1.3 and when the resistancebetween the electrodes falls within the range from 0.2 to 20MV. The meter shall be protected from stray electrostatic fieldsso that no permanent change in the meter readings over theentire operating range is produced by touching with a groun
42、dedlead, any part of the exposed surface of the glass electrode, theglass electrode lead, the titration stand, or the meter. Adesirable apparatus may consist of a continuous-reading elec-tronic voltmeter with specified range, accuracy, and sensitivity,that is designed to operate on an input of less
43、than 5 3 1012Awhen an electrode system having 1000 MV resistance isconnected across the meter terminals; that is provided with ametal shield connected to the ground; and is provided with asatisfactory terminal to connect the shielded connection wirefrom the glass electrode to the meter without inter
44、ference fromthe presence of external electrostatic fields.A1.2 Glass ElectrodeA1.2.1 A pencil-type glass electrode 125 to 180 mm inlength and 8 to 14 mm in diameter. The body of the electrodeshall be made of a chemically resistant glass tube with a wallthickness of 1 to 3 mm. The end dipping into th
45、e solution shallbe closed with a hemisphere of glass4sealed on the electrodetube and the radius of this hemisphere shall be above 7 mm.The thickness of the glass in the hemisphere shall be greatenough so that resistance of the hemisphere is 100 to 1000 mVat 25C. The electrode shall contain a reprodu
46、cible, perma-nently sealed liquid cell for making electrical connections withthe inner surface of the hemisphere. The entire electricalconnection, from the sealed contact cell to the meter terminal,shall be surrounded by an electrical shield that will preventelectrostatic interference when the shiel
47、d is grounded. Theshield shall be insulated from the electrical connection byinsulating material of the highest quality, such as rubber andglass, so that the resistance between the shield and the entirelength of electrical connection is greater than 50 000 MV.A1.3 Calomel ElectrodeA1.3.1 A pencil-ty
48、pe calomel electrode 125 to 180 mm inlength and 8 to 14 mm in diameter. This electrode shall bemade of glass and shall be provided with an external, remov-able glass sleeve on the sealed end that is dipped into thetitration solution. The glass sleeve shall be 8 to 25 mm inlength, shall be slightly t
49、apered, and shall be ground to fit theelectrode, so that the sealed end of the electrode protrudes 2 to20 mm beyond the sleeve. The ground surface shall becontinuous and free of smooth spots. At a point midwaybetween the extremities of the ground surface, the electrodeshall be pierced by a hole or holes 1 mm in diameter. Theelectrode shall contain the necessary mercury, calomel, andelectrical connection to the mercury, all arranged in a perma-nent manner. The electrode shall be filled almost to capacitywith saturated KCl electrolyte and shall be equipp
