ASTM_D_1126_-_12.pdf

Designation:D112612Standard Test Method forHardness in Water1This standard is issued under the fixed designation D1126;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.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 hardness inwater by titration.This test method is applicable to waters thatare clear in appearance and free of chemicals that will complexcalcium or magnesium.The lower detection limit of this testmethod is approximately 2 to 5 mg/Las CaCO3;the upper limitcan be extended to all concentrations by sample dilution.It ispossible to differentiate between hardness due to calcium ionsand that due to magnesium ions by this test method.1.2 This test method was tested on reagent water only.It isthe users responsibility to ensure the validity of the testmethod for waters of untested matrices.1.3 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.4 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:2D1066 Practice for Sampling SteamD1129 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 equivalent per million(epm),na unit chemicalequivalent weight of solute per million unit weights of solu-tion.3.2.2 laboratory control sample(LCS),na solution withcertified hardness.4.Summary of Test Method4.1 Calcium and magnesium ions in water are sequesteredby the addition of disodium ethylenediamine tetraacetate.Theend point of the reaction is detected by means of Chrome BlackT3,which has a red color in the presence of calcium andmagnesium and a blue color when they are sequestered.5.Significance and Use5.1 Hardnesssaltsinwater,notablycalciumandmagnesium,are the primary cause of tube and pipe scaling,which frequently causes failures and loss of process efficiencydue to clogging or loss of heat transfer,or both.5.2 Hardness is caused by any polyvalent cations,but thoseother than Ca and Mg are seldom present in more than traceamounts.The term hardness was originally applied to water inwhich it was hard to wash;it referred to the soap-wastingproperties of water.With most normal alkaline water,thesesoap-wasting properties are directly related to the calcium andmagnesium content.6.Interferences6.1 The substances shown in Table 1 represent the highestconcentrations that have been found not to interfere with thisdetermination.6.2 The test method is not suitable for highly coloredwaters,which obscure the color change of the indicator.1This 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 March 1,2012.Published March 2012.Originallyapproved in 1950.Last previous edition approved in 2007 as D1126 02(2007)1.DOI:10.1520/D1126-12.2For 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.33Hydroxy4-(1hydroxy-2napththyl)azo-7nitro1 naphthalenesulfonicacid,sodium salt,Color Index 14645.*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 7.Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended thatall reagents shall conform to the specifications of the Commit-tee onAnalytical Reagents of theAmerican Chemical Society.4Other grades may be used,provided it is first ascertained thatthe reagent is of sufficiently high purity to permit its usewithout lessening the accuracy of the determination.7.2 Purity of WaterUnless otherwise indicated,referenceto water shall be understood to mean reagent water conformingto Specification D1193,Type I.Other reagent water types maybe used provided it is first ascertained that the water is ofsufficiently high purity to permit its