ASTM D1067-2006 Standard Test Methods for Acidity or Alkalinity of Water《测定水酸碱性的标准测试方法》.pdf

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1、Designation: D 1067 06An American National StandardStandard Test Methods forAcidity or Alkalinity of Water1This standard is issued under the fixed designation D 1067; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last

2、 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 These test methods2cover the determinat

3、ion of acidityor alkalinity of all types of water. Three test methods are givenas follows:SectionsTest Method A (Electrometric Titration) 7 to 15Test Method B (Electrometric or Color-Change Titration) 16 to 24Test Method C (Color-Change Titration After HydrogenPeroxide Oxidation and Boiling)25 to 33

4、1.2 In all of these test methods the hydrogen or hydroxylions present in water by virtue of the dissociation or hydrolysisof its solutes, or both, are neutralized by titration with standardalkali (acidity) or acid (alkalinity). Of the three procedures,Test Method A is the most precise and accurate.

5、It is used todevelop an electrometric titration curve (sometimes referred toas a pH curve), which defines the acidity or alkalinity of thesample and indicates inflection points and buffering capacity, ifany. In addition, the acidity or alkalinity can be determinedwith respect to any pH of particular

6、 interest. The other twomethods are used to determine acidity or alkalinity relative toa predesignated end point based on the change in color of aninternal indicator or the equivalent end point measured by a pHmeter. They are suitable for routine control purposes.1.3 When titrating to a specific end

7、 point, the choice of endpoint will require a careful analysis of the titration curve, theeffects of any anticipated changes in composition on thetitration curve, knowledge of the intended uses or dispositionof the water, and a knowledge of the characteristics of theprocess controls involved. While

8、inflection points (rapidchanges in pH) are usually preferred for accurate analysis ofsample composition and obtaining the best precision, the use ofan inflection point for process control may result in significanterrors in chemical treatment or process control in someapplications. When titrating to

9、a selected end point dictated bypractical considerations, (1) only a part of the actual neutral-izing capacity of the water may be measured, or (2) thiscapacity may actually be exceeded in arriving at optimumacidity or alkalinity conditions.1.4 A scope section is provided in each test method as agui

10、de. It is the responsibility of the analyst to determine theacceptability of these test methods for each matrix.1.5 Former Test Methods C (Color-Comparison Titration)and D (Color-Change Titration After Boiling) were discontin-ued. Refer to Appendix X4 for historical information.1.6 The values stated

11、 in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.7 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 safety and h

12、ealth practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D 596 Guide for Reporting Results of Analysis of WaterD 1066 Practice for Sampling SteamD 1129 Terminology Relating to WaterD 1193 Specification for Reagent WaterD 1293

13、Test Methods for pH of WaterD 2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD 3370 Practices for Sampling Water from Closed ConduitsD 5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water AnalysisE 200 P

14、ractice for Preparation, Standardization, and Stor-age of Standard and Reagent Solutions for ChemicalAnalysis3. Terminology3.1 DefinitionsThe terms in these test methods are definedin accordance with Terminology D 1129.1These test methods are under the jurisdiction of ASTM Committee D19 onWater and

15、are the responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Dec. 15, 2006. Published January 2007. Originallyapproved in 1949. Last previous edition approved in 2002 as D 1067 02.2The basic procedures used in these test methods have appeared widespread in

16、the technical literature for many years. Only the particular adaptation of theelectrometric titration appearing as the Referee Method is believed to be largely thework of Committee D19.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceast

17、m.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 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United St

18、ates.3.1.1 Certain uses of terminology exist in the water treat-ment industry which may differ from these definitions. Adiscussion of terms is presented in Appendix X1.4. Significance and Use4.1 Acidity and alkalinity measurements are used to assist inestablishing levels of chemical treatment to con

19、trol scale,corrosion, and other adverse chemical equilibria.4.2 Levels of acidity or alkalinity are critical in establishingsolubilities of some metals, toxicity of some metals, and thebuffering capacity of some waters.5. Purity of Reagents5.1 Reagent grade chemicals shall be used in all tests.Unles

20、s otherwise indicated, it is intended that all reagents shallconform to the specifications of the Committee on AnalyticalReagents of the American Chemical Society, where suchspecifications are available.4Other grades may be used, pro-vided it is first ascertained that the reagent is of sufficientlyh

21、igh purity to permit its use without lessening the accuracy ofthe determination.5.2 Unless otherwise indicated, references to water shall beunderstood to mean reagent water conforming to SpecificationD 1193, Type I. In addition, reagent water for this test shall befree of carbon dioxide (CO2) and sh

22、all have a pH between 6.2and 7.2 at 25C. Other reagent water types may be usedprovided it is first ascertained that the water is of sufficientlyhigh purity to permit its use without adversely affecting theprecision and bias of the test method. Type III water wasspecified at the time of round robin t

23、esting of this test method.A procedure for the preparation of carbon dioxide-free water isgiven in Practice E 200.6. Sampling6.1 Collect the sample in accordance with Practice D 1066and Practices D 3370 as applicable.6.2 The time interval between sampling and analysis shallbe as short as practically

24、 possible in all cases. It is mandatorythat analyses by Test Method A be carried out the same day thesamples are taken; essentially immediate analysis is desirablefor those waste waters containing hydrolyzable salts thatcontain cations in several oxidation states.TEST METHOD AELECTROMETRIC TITRATION

25、7. Scope7.1 This test method is applicable to the determination ofacidity or alkalinity of all waters that are free of constituentsthat interfere with electrometric pH measurements. It is usedfor the development of a titration curve that will defineinflection points and indicate buffering capacity,

26、if any. Theacidity or alkalinity of the water or that relative to a particularpH is determined from the curve.8. Summary of Test Method8.1 To develop a titration curve that will properly identifythe inflection points, standard acid or alkali is added to thesample in small increments and a pH reading

27、 is taken after eachaddition. The cumulative volume of solution added is plottedagainst the observed pH values. All pH measurements aremade electrometrically.9. Interferences9.1 Although oily matter, soaps, suspended solids, and otherwaste materials may interfere with the pH measurement, thesemateri

28、als may not be removed to increase precision, becausesome are an important component of the acid- or alkali-consuming property of the sample. Similarly, the developmentof a precipitate during titration may make the glass electrodesluggish and cause high results.10. Apparatus10.1 Electrometric pH Mea

29、surement Apparatus, conform-ing to the requirements given in Test Methods D 1293.11. Reagents411.1 Hydrochloric Acid, Standard (0.02 N) (see Note 1)Prepare and standardize as directed in Practice E 200, exceptthat the titration shall be made electrometrically. The inflectionpoint corresponding to th

30、e complete titration of carbonic acidsalts will be very close to pH 3.9.NOTE 1Sulfuric acid of similar normality may be used instead ofhydrochloric acid. Prepare and standardize in like manner.11.2 Sodium Hydroxide, Standard (0.02 N)Prepare andstandardize as directed in Practice E 200, except that t

31、hetitration shall be made electrometrically. The inflection pointcorresponding to the complete titration of the phthalic acid saltwill be very close to pH 8.6.12. Procedure12.1 Mount the glass and reference electrodes in two of theholes of a clean, threehole rubber stopper chosen to fit a300-mL, tal

32、l-form Berzelius beaker without spout, or equiva-lent apparatus. Alternatively, a combination pH electrode canbe used that has both a glass and a reference electrode in anintegral unit. Place the electrodes in the beaker and standardizethe pH meter, using a reference buffer having a pH approxi-matin

33、g that expected for the sample (see Test MethodsD 1293). Rinse the electrodes, first with reagent water, thenwith a portion of the sample. Following the final rinse, drainthe beaker and electrodes completely.12.2 Pipette 100 mL of the sample, adjusted, if necessary, toroom temperature, into the beak

34、er through the third hole in thestopper. Hold the tip of the pipette near the bottom of thebeaker while discharging the sample.12.3 Measure the pH of the sample in accordance with TestMethods D 1293.12.4 Add either 0.02 N acid or alkali solution, as indicated,in increments of 0.5 mL or less (see Not

35、e 2). After each4Reagent 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 the United

36、States Pharmacopoeiaand National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,MD.D 1067 062addition, mix the solution thoroughly. Determine the pH whenthe mixture has reached equilibrium as indicated by a constantreading (see Note 3). Mechanical stirring, preferably of themagneti

37、c type, is required for this operation; mixing by meansof a gas stream is not permitted. Continue the titration until thenecessary data for the titration curve have been obtained.NOTE 2If the sample requires appreciably more than 25 mL ofstandard solution for its titration, use a smaller aliquot, or

38、 a 0.1 N solution,prepared and standardized in the same manner (see Practice E 200).NOTE 3An electrometric titration curve is smooth, with the pHchanging progressively in a single direction, if equilibrium is achievedafter each incremental addition of titrant, and may contain one or moreinflection p

39、oints. Ragged or irregular curves may indicate that equilibriumwas not attained before adding succeeding increments. The time requiredwill vary with different waters as the reaction rate constants of differentchemical equilibria vary. In some instances the reaction time may be aninterval of a few se

40、conds while other slower, more complex reactions mayrequire much longer intervals. It is important, therefore, that the period besufficient to allow for any significant pH changes, yet consistent with goodlaboratory practices.12.5 To develop a titration curve, plot the cumulativemilliliters of stand

41、ard solution added to the sample aliquotagainst the observed pH values. The acidity or alkalinityrelative to a particular pH may be determined from the curve.13. Calculation13.1 Calculate the acidity or alkalinity, in milliequivalentsper litre, using Eq 1:Acidity or alkalinity!, meq/L epm!5AN/B 3 10

42、00 (1)where:A = standard acid or alkali required for the titration, mL,N = normality of the standard solution, andB = sample titrated, mL.14. Report14.1 Report the results of titrations to specific end points asfollows: “The acidity (or alkalinity) to pH at C = meq/L(epm).”14.2 Appropriate factors f

43、or converting milliequivalents perlitre (epm) to other units are given in Guide D 596.15. Precision and Bias515.1 The precision and bias data presented in Table 1 forthis test method meet the requirements of Practice D 2777.15.2 The collaborative test of this test method was per-formed in reagent wa

44、ters by six laboratories using one operatoreach, using three levels of concentration for both the acidityand alkalinity.15.3 Precision and bias for this test method conforms toPractice D 277777, which was in place at the time ofcollaborative testing. Under the allowances made in 1.4 ofPractice D 277

45、798, these precision and bias data do meetexisting requirements for interlaboratory studies of CommitteeD19 test methods.TEST METHOD BELECTROMETRIC ORCOLOR-CHANGE TITRATION16. Scope16.1 This test method covers the rapid, routine controlmeasurement of acidity or alkalinity to predesignated endpoints

46、of waters that contain no materials that buffer at the endpoint or other materials that interfere with the titration byreasons that may include color or precipitation.17. Summary of Test Method17.1 The sample is titrated with standard acid or alkali to adesignated pH, the end point being determined

47、electrometri-cally or by the color change of an internal indicator.18. Interferences18.1 Natural color or the formation of a precipitate whiletitrating the sample may mask the color change of an internalindicator. Suspended solids may interfere in electrometrictitrations by making the glass electrod

48、e sluggish. Waste mate-rials present in some waters may interfere chemically withcolor titrations by destroying the indicator. Variable resultsmay be experienced with waters containing oxidizing orreducing substances, depending on the equilibrium conditionsand the manner in which the sample is handl

49、ed.19. Apparatus19.1 Electrometric pH Measurement ApparatusSee 10.1.20. Reagents20.1 Bromcresol Green Indicator Solution (l g/L)Dissolve0.1 g of bromcresol green in 2.9 mL of 0.02 N sodiumhydroxide (NaOH) solution. Dilute to 100 mL with water.20.2 Hydrochloric Acid, Standard (0.02 N)(Note 1)See11.1, except that the acid may be standardized by colorimetrictitration as directed in Practice E 200 when an indicator is usedfor sample titration.20.3 Methyl Orange Indicator Solution (0.5 g/L)Dissolve0.05 g of methyl orange in water and dilute to 100 mL.20.4 Methyl Purple I