ASTM_D_1293_-_12.pdf

Designation:D129312Standard Test Methods forpH of Water1This standard is issued under the fixed designation D1293;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 U.S.Department of Defense.1.Scope1.1 These test methods cover the determination of pH byelectrometric measurement using the glass electrode as thesensor.Two test methods are given as follows:SectionsTest Method APrecise Laboratory Measurement8 to 15Test Method BRoutine or Continuous Measurement16 to 241.2 Test Method A covers the precise measurement of pH inwater utilizing at least two of seven standard reference buffersolutions for instrument standardization.1.3 Test Method B covers the routine measurement of pH inwater and is especially useful for continuous monitoring.Twobuffers are used to standardize the instrument under controlledparameters,but the conditions are somewhat less restrictivethan those in Test MethodA.For on-line measurement,also seeTest Method D6569 which provides more detail.1.4 Both test methods are based on the pH scale establishedby NIST(formerly NBS)Standard Reference Materials.21.5 Neither test method is considered to be adequate formeasurement of pH in water whose conductivity is less thanabout 5 S/cm.Refer to Test Methods D5128 and D5464.1.6 Precision and bias data were obtained using buffersolutions only.It is the users responsibility to assure thevalidity of these test methods for untested types of water.1.7 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.8 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:3D1066 Practice for Sampling SteamD1067 Test Methods for Acidity or Alkalinity of WaterD1129 Terminology Relating to WaterD1192 Guide for Equipment for Sampling Water and Steamin Closed Conduits(Withdrawn 2003)4D1193 Specification for Reagent WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370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 ConduitsD5128 Test Method for On-Line pH Measurement of Waterof Low ConductivityD5464 Test Method for pH Measurement of Water of LowConductivityD6569 Test Method for On-Line Measurement of pHE70 Test Method for pH of Aqueous Solutions With theGlass Electrode3.Terminology3.1 DefinitionsFor definitions of terms used in these testmethods,refer to Terminology D1129.3.2 Definitions of Terms Specific to This Standard:3.2.1 pH,nthe negative logarithm of the hydrogen ionactivity in an aqueous solution or the logarithm of thereciprocal of the hydrogen ion activity.3.2.1.1 Discussionthe pH of an aqueous solution is de-rived from E,the electromotive force(emf)of the cellglass electrode|solution|reference electrode(where the double vertical line represents a liquid junc-tion)when the electrodes are immersed in the solution in thediagrammed position,and Esis the electromotive force ob-tained when the electrodes are immersed in a reference buf-fer solution.With the assigned pH of the reference buffer designated as1These test methods are under the jurisdiction of ASTM Committee D19 onWater and are the direct responsibility of Subcommittee D19.03 on Sampling Waterand Water-Formed Deposits,Analysis of Water for Power Generation and ProcessUse,On-Line Water Analysis,and Surveillance of Water.Current edition approved Jan.1,2012.Published January 2012.Originallyapproved in 1953.Last previous edition approved in 2005 as D1293 99(2005).DOI:10.1520/D1293-11.2“Standard Reference Materials:Standardization of pH Measurements”Wu andKoch,NBS Special Publications No.260-53,1988.3For 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.4The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 pHs,and E and Esexpressed in volts is the following:5pH5 pHs1E 2 Es!F2.3026 RTwhere:F=Faraday constant,R=gas constant,andT=absolute temperature,t(C)+273.15.The reciprocal of F/2.3026 RT is known as the slope of theelectrode,and is the expected difference in observed voltagefor two measurements one pH unit apart.Values of the slope atvarious temperatures are given in Table 1.4.Summary of Test Method4.1 The pH meter and associa