1、Designation: D 1253 03Standard Test Method forResidual Chlorine in Water1This standard is issued under the fixed designation D 1253; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses
2、 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 test method covers the determination of residualchlorine in water by
3、 direct amperometric titration.1.2 Within the constraints specified in Section 6, this testmethod is not subject to commonly encountered interferencesand is applicable to most waters. Some waters, however, canexert an iodine demand, usually because of organic material,making less iodine available fo
4、r measurement by this testmethod. Thus, it is possible to obtain falsely low chlorinereadings, even though the test method is working properly,without the users knowledge.1.3 Precision data for this test method were obtained onestuary, inland main stem river, fresh lake, open ocean, andfresh cooling
5、 tower blowdown water. Bias data could not bedetermined because of the instability of solutions of chlorine inwater. It is the users responsibility to ensure the validity of thetest method for untested types of water.1.4 In the testing by which this standard was validated, thedirect and back starch-
6、iodide titrations and the amperometricback titration, formerly part of this standard, were found to beunworkable and were discontinued in 1986. Historical infor-mation is presented in Appendix X1.NOTE 1Orthotolidine test methods have been omitted because of poorprecision and accuracy.1.5 This standa
7、rd 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 health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 AST
8、M Standards:D 1129 Terminology Relating to Water2D 1193 Specification for Reagent Water2D 2777 Practice for Determination of Precision and Bias ofApplicable Methods of Committee D19 on Water2D 3370 Practices for Sampling Water from Closed Con-duits2D 5847 Practice for Writing Quality Control Specifi
9、cationsfor Standard Test Methods for Water Analysis33. Terminology3.1 Definitions: For definitions of terms used in this testmethod, refer to Terminology D 1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 combined residual chlorine, nresidual consisting ofchlorine combined with ammonia
10、nitrogen or nitrogenouscompounds.3.2.2 free available chlorine residual, nresidual consist-ing of hypochlorite ions, hypochlorous acid, or a combinationthereof.3.2.3 total residual chlorine (chlorine residual), ntheamount of available chlorine-induced oxidants present in waterat any specified period
11、, subsequent to the addition of chlorine.NOTE 2Chlorine present as chloride is neither included in these termsnor determined by this test method.NOTE 3Bromine, bromine combined with ammonia or nitrogenouscompounds, and chlorine dioxide are not distinguished by this test methodfrom the corresponding
12、chlorine compounds.4. Summary of Test Method4.1 This is an amperometric titration test method utilizingphenylarsine oxide as the titrant. When the titrator cell isimmersed in a sample containing chlorine, current is generated.As phenylarsine oxide is added, the chlorine is reduced and thegeneration
13、of current ceases. When chlorine is present as achloramine, potassium iodide is added, releasing iodine, whichis titrated in a similar manner. The iodine content is calculatedin terms of free chlorine.5. Significance and Use5.1 Chlorine is used to destroy or deactivate a variety ofunwanted chemicals
14、 and microorganisms in water and waste-water.5.2 An uncontrolled excess of chlorine in water, whetherfree available or combined, can adversely affect the subsequentuse of the water.1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommit
15、tee D19.05 on Inorganic Constituentsin Water.Current edition approved June 10, 2003. Published July 2003. Originallyapproved in 1953. Last previous edition approved in 1996 as D 1253 86 (1996).2Annual Book of ASTM Standards, Vol 11.01.3Annual Book of ASTM Standards, Vol 11.02.1*A Summary of Changes
16、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.6. Interferences6.1 This test method is not subject to interferences fromtemperature, color, or turbidity of sample.6.2 Values of pH above 8.0
17、 interfere by slowing the reactionrate. Buffering the sample to pH 7.0 or less eliminates theinterference.6.3 Erratic behavior of the apparatus in the presence ofcupric ions has been reported.6.4 Cuprous and silver ions tend to poison the electrode ofthe titrator.6.5 Nitrogen trichloride and some N-
18、chloro compounds areoften present as products of the chlorination of wastewatersand will titrate partially as free available chlorine and partiallyas combined residual chlorine. This error can be avoided onlyin the determination of total residual chlorine.6.6 Exposure to high concentrations of free
19、available chlo-rine causes a film-type polarization that reverses very slowly.This can be avoided by diluting the sample with water to lessthan 10 mg/L of free available chlorine.6.7 If chlorine dioxide is present, an unknown portiontitrates as free available chlorine. Total chlorine dioxide titrate
20、sas total residual chlorine.6.8 Depending upon final pH, chlorination of waters con-taining ammonia or nitrogenous organic compounds can pro-duce high concentrations of dichloramine. This compoundproduces four to five times as much current as monochloram-ine. The current produced by as little as 5 m
21、g/L of dichloram-ine can cause the microammeter pointer to read offscale even atthe end point in the titration of free available chlorine. Thismay be overcome by use of an opposing voltage in theapparatus circuitry. The instruments manufacturer should beconsulted in this regard.7. Apparatus7.1 Amper
22、ometric Titration Apparatus4,5Refer to Fig. 1.NOTE 4When the titrator has been out of service for a day or more,check the electrode for sensitivity by noting the rapidity of the pointerdeflection. If the pointer responds slowly after the addition of KI solution,add a small amount of biiodate. If it
23、responds slowly to free availablechlorine, sensitize it by adding chlorine.7.2 GlasswareCondition with water containing at least 10mg/L of residual chlorine for at least 2 h prior to use and thenrinse thoroughly.8. Reagents and Materials8.1 Purity of ReagentsReagent grade chemicals shall beused in a
24、ll tests. Unless otherwise indicated, it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.6Other grades may be used, provided it is first ascertained that4Water and Sewage Works, May 1949, p. 171, and Journal Ame
25、rican WaterWorks Association, Vol 34, 1942, pp. 12271240.5Amperometric titrators are available commercially from most laboratory supplyhouses.6Reagent Chemicals, American Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted b
26、y 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.FIG. 1 Wiring Diagram of Amperometric TitratorD 1253 032the reagent is of s
27、ufficiently high purity to permit its usewithout lessening the accuracy of the determination.8.2 Purity of WaterUnless otherwise indicated, referencesto water shall be understood to mean reagent water conformingto Specification D 1193, Type III, further treated to be free ofchlorine demand. A sugges
28、ted method for preparation ofchlorine demand-free water is to add approximately 20 mg/Lofavailable chlorine to Type III water, let it stand for about aweek in darkness, and then expose it to sunlight until nochlorine remains.8.3 pH 4.0 Buffer SolutionDissolve 243 g of sodiumacetate trihydrate and 48
29、0 g of glacial acetic acid in water anddilute to 1 L.8.4 pH 7.0 Buffer SolutionDissolve 25.4 g of monobasicpotassium phosphate and 86 g of dibasic sodium phosphate inwater and dilute to 1 L.8.5 Biiodate, Solution Standard (0.0282N)Dissolve0.9163 g of potassium biiodate in water and dilute to 1 L in
30、avolumetric flask. Store in an amber glass-stoppered bottle.8.6 Phenylarsine Oxide, Solution Standard(0.00564 N)Dissolve 0.8 g of phenylarsine oxide in 150 mL of sodiumhydroxide solution (12 g/L). After settling, decant 110 mL ofthis solution, add 800 mL of water, and bring to a pH of 9.0 byadding h
31、ydrochloric acid (1 + 1). This should require about 2mL of HCl (1 + 1). Continue acidification with HCl (1 + 1)until a pH of 6 to 7 is reached, as indicated by a glass-electrodesystem; then dilute to a total volume of 1L. Standardize to0.00564 N against 0.0282 N biiodate solution using the titrator(
32、7.1) as the end-point indicator. Add 1 mL of chloroform forpreservation.8.7 Potassium Iodide Solution (50 g/L)Dissolve 50 g ofKI in water and dilute to 1 L. Add1gofsodium bicarbonateto stabilize the solution. Store in an amber bottle and avoiddirect exposure to sunlight.9. Sampling9.1 Collect the sa
33、mple in accordance with Practices D 3370.Take care that the sample is representative and keep it awayfrom direct sunlight prior to analysis.9.2 All tests should be made as soon as possible aftercollection of the sample (not more than 5 min) because theresidual chlorine may diminish with time, due to
34、 the chlorinedemand of the sample. Where time of contact is important, theelapsed time between the addition of chlorine and the deter-mination of chlorine should be taken into account.10. Procedure10.1 For residual chlorine concentrations of 2.0 mg/L orless, use a 200-mL sample. For greater concentr
35、ations, use a100-mL sample. It is preferable that the size of the sample besuch that not more than 2 mL of titrant will be required tocomplete the titration.10.2 Determination of Total Residual Chlorine:10.2.1 Add 1 mL of KI solution to a 200-mL sample andimmediately add 1 mL of pH 4.0 buffer soluti
36、on.10.2.2 Immerse the electrodes in the sample and start thestirrer. Adjust the microammeter pointer of the potentiometerto the right or high current side of the scale so the pointer candeflect counterclockwise during the analysis.10.2.3 Titrate using standard phenylarsine oxide solution,adding the
37、titrant in small increments, and noting the deflectionof the microammeter pointer. Plot the progress of the titrationon linear graph paper with current on the vertical axis andtitrant volume on the horizontal axis. Add a small volume oftitrant, wait a few seconds, and plot the current-volume pointon
38、 the graph.10.2.4 Readjust the potentiometer several times during thetitration, if necessary, to bring the pointer back on scale.10.2.5 Continue the analysis by determining at least threepoints spread over the downward sloping titration curve and atleast three points after the equivalence or end poi
39、nt. The latterpoints will indicate practically no change in current. Points justbefore the end point shall be disregarded in its determination.The millilitres of titrant at the end point defined by theintersection of the two linear sections of the titration curveshould be recorded.10.3 Determination
40、 of Free Available Chlorine Residual:10.3.1 Add 1 mL of pH 7.0 buffer solution to a 200-mLsample.10.3.2 Repeat the phenylarsine oxide titration beginningwith 10.2.2.10.3.3 Note a rapid deflection of the pointer for eachincrement of titrant indicates the presence of free availablechlorine. Slight cou
41、nterclockwise movements of the pointerafter addition of individual drops of titrant is a drift effect anddoes not indicate the presence of free available chlorine.10.4 Determination of Combined Available Chlorine Re-sidual:10.4.1 Complete the titration for the determination of freeavailable chlorine
42、 residual as in 10.3.10.4.2 To the same sample, add 1 mL of KI solution and 1mL of pH 4.0 buffer solution and repeat the titration as in 10.2.11. Calculation11.1 Calculate the various types of chlorine residual, inmilligrams per litre, as follows:Chlorine residual, mg/L 5 200 A/Vwhere:A = phenylarsi
43、ne oxide solution (0.00564 N) required forthe titration of 10.2, 10.3,or10.4, depending on thespecific type of chlorine residual determined, mL, andV = sample used, mL.12. Precision and Bias712.1 The overall precision (St) and the single operatorprecision (So) of this test method for free available
44、chlorine(FAC) and for total residual chlorine (TRC) were determinedby eight or nine qualified cooperators each with analysisequipment and reagents at each of five sites. Each siteconstituted a different chlorinated cooling water matrix: estu-ary, inland main stem river, fresh lake, open ocean, and f
45、reshcooling tower blowdown. Each site water was chlorinated up to7Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: D191124.D 1253 033nine levels. Samples were collected simultaneously and ana-lyzed within 5 min of collection by a
46、ll eight or nine coopera-tors. Duplicate sampling and analysis runs were made at eachlevel.12.2 The Stand Sofor FAC was found to vary linearly withthe mean concentration of FAC, X, in mg/L, over the range forX from 0.0 to 1.0.12.2.1 For the pooled results from all of the matrices tested:St5 0.025 1
47、0.199 X n 5 37, r 5 0.848!So5 0.008 1 0.081 X n 5 35, r 5 0.638!where:n = number of runs, andr = correlation coefficients.12.3 The Stand Sofor TRC was found to vary linearly withthe mean concentration of TRC, Y, in mg/L, over the range forY from 0.0 to 3.5.12.3.1 For the pooled results from all of t
48、he matrices tested:St5 0.022 1 0.098 Y n 5 39, r 5 0.865!So5 0.012 1 0.024 Y n 5 38, r 5 0.695!12.4 The bias of the test method could not be determinedsince the instability of solutions of chlorine in water does notpermit the determination of an acceptable true value for TRCand FAC in the samples.12
49、.5 Precision for this test method conforms to Practice D277777, which was in place at the time of collaborativetesting. Under the allowances made in 1.4 of Practice D277798, these precision data do meet existing requirementsfor interlaboratory studies of Committee D19 test methods.13. Quality Control13.1 In order to be certain that analytical values obtainedusing these test methods are valid and accurate within theconfidence limits of the test, the following QC procedures shallbe followed when analyzing residual chlorine.13.2 Calibration and Calibratio
