ASTM_D_1253_-_14.pdf

Designation:D125314Standard Test Method forResidual Chlorine in Water1This standard is issued under the fixed designation D1253;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 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 covers the determination of residualchlorine in water by 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 for 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 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-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.NOTE1Orthotolidine test methods have been omitted because of poorprecision and accuracy.1.5 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.6 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 health practices and determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D1129 Terminology Relating to WaterD1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD5847 Practice for Writing Quality Control Specificationsfor Standard Test Methods for Water Analysis3.Terminology3.1 DefinitionsFor definitions of terms used in this testmethod,refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 combined residual chlorine,nresidual consisting ofchlorine combined with ammonia 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,subsequent to the addition of chlorine.3.2.3.1 DiscussionChlorine present as chloride is neitherincluded in these terms nor determined by this test method.Bromine,bromine combined with ammonia or nitrogenouscompounds,and chlorine dioxide are not distinguished by thistest method from the corresponding 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 of current ceases.When chlorine is present as a1This test method is under the jurisdiction of ASTM Committee D19 on Waterand is the direct responsibility of Subcommittee D19.05 on Inorganic Constituentsin Water.Current edition approved Jan.15,2014.Published February 2014.Originallyapproved in 1953.Last previous edition approved in 2008 as D1253 08.DOI:10.1520/D1253-14.2For 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 page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 chloramine,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 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.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 interfere by slowing the reactionrate.Buffering the sample to pH