ASTM_D_5464_-_16.pdf

Designation:D546416Standard Test Method forpH Measurement of Water of Low Conductivity1This standard is issued under the fixed designation D5464;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.Scope1.1 This test method is applicable to determine the pH ofwater samples with a conductivity of 2 to 100 S/cm over thepH range of 3 to 11 and is frequently used in power generationlow conductivity samples.pH measurements of water of lowconductivity are problematic.Specifically,this test methodavoids contamination of the sample with atmospheric gasesand prevents volatile components of the sample from escaping.This test method provides for pH electrodes and apparatus thataddress additional considerations discussed in Annex A2.Thistest method also minimizes problems associated with thesamples pH temperature coefficient when the operator usesthis test method to calibrate an on-line pH monitor or controller(see Appendix X1).1.2 This test method covers the measurement of pH in waterof low conductivity with a lower limit of 2.0 S/cm,utilizinga static grab-sample procedure where it is not practicable totake a real-time flowing sample.NOTE1Test Method D5128 for on-line measurement is preferred overthis method whenever possible.Test Method D5128 is not subject to thelimited conductivity range,temperature interferences,potential KClcontamination,and time limitations found with this method.1.3 For on-line measurements in water with conductivity of100 S/cm and higher,see Test Method D6569.1.4 For laboratory measurements in water with conductivityof 100 S/cm and higher,see Test Method D1293.1.5 The values stated in SI units are to be regarded asstandard.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 WaterD1293 Test Methods for pH of WaterD2777 Practice for Determination of Precision and Bias ofApplicable Test Methods of Committee D19 on WaterD3370 Practices for Sampling Water from Closed ConduitsD4453 Practice for Handling of High Purity Water SamplesD5128 Test Method for On-Line pH Measurement of Waterof Low ConductivityD6569 Test Method for On-Line Measurement of pH3.Terminology3.1 Definitions of TermsFor definitions of terms used inthis test method,refer to Terminology D1129.3.2 Definitions:3.3 Definitions of Terms Specific to This Standard:3.3.1 liquid-junction potential,na dc potential that ap-pears at the point of contact between the reference electrodessalt bridge(also known as reference junction or diaphragm)and the sample solution.3.3.1.1 DiscussionIdeally,this potential is near zero and isstable.However,in low-conductivity water this potential maychange from its value in buffer solution by an unknownamount,and is a zero offset(1).34.Reagents4.1 Purity of ReagentsReagent grade chemicals shall beused in all tests.Unless otherwise indicated,it is intended that1These 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 WaterCurrent edition approved June 1,2016.Published June 2016.Originallyapproved in 1993.Last previous edition approved in 2011 as D5464 11.DOI:10.1520/D5464-16.2For 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.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 all reagents conform to the specifications of the Committee onAnalytical Reagents of the American Chemical Society wheresuch specifications are available.4Other grades may be used,provided it is first ascertained that the reagent is of sufficientlyhigh purity to permit its use without lessening the accuracy ofthe determination.4.2 Purity of WaterReferences to water that is used forreagent preparation,rinsing or dilution shall be understood tomean water that conforms to the quantitative specifications ofType II reagent water of Specification D1193.4.3 Commercial Buffer Solutions Commercially availableprepared buffers traceable to NIST standards should be ad-equate to perform the calibration procedures in 10.1 10.4.The exact pH of