ASTM_D_4972_-_19.pdf

Designation:D497219Standard Test Methods forpH of Soils1This standard is issued under the fixed designation D4972;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 These test methods cover the measurement of the pH ofsoils that will pass the 2.00 mm(No.10)sieve.Suchmeasurements are used in the agricultural,environmental,geotechnical,and natural resources fields.This measurementdetermines the degree of acidity or alkalinity in soil materialssuspended in water and a 0.01 M calcium chloride solution.Measurements in both liquids are necessary to fully define thesoils pH.This variable is useful in determining the solubilityof soil minerals and the mobility of ions in the soil andassessing the viability of the soil-plant environment.A moredetailed discussion of the usefulness of this parameter is givenin Refs(1-6)2.1.2 Two methods for measuring the pH of soils are pro-vided.The method to be used shall be specified by therequesting authority.When no method is specified,Method Ashall be used.The pH is determined in test water and a calciumchloride solution for both methods.1.2.1 Method AThe pH is measured using a potentiometerhaving a pH sensitive electrode system.This method can beused for any application and must be used when the applicationwarrants a higher level of resolution.1.2.2 Method BThe pH is measured using pH sensitivepaper.This method can be used for any application,however,because paper typically has a lower resolution,it provides anapproximate estimate of the pH of the soil and should not beused when the application requires a higher level of resolution(Note 1).NOTE1For example,paper with a sensitivity to the nearest 1 pH unitplaced into a buffer solution of 4 should indicate a pH of 4,however,itwould not indicate if the pH is 4.449 or 3.449.1.3 UnitsThe values stated in SI units are to be regardedas standard.No other units of measurement are included in thisstandard.1.4 All measured and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D6026.1.4.1 The procedures used to specify how data are collected/recorded and calculated in the standard are regarded as theindustry standard.In addition,they are representative of thesignificant digits that generally should be retained.The proce-dures used do not consider material variation,purpose forobtaining the data,special purpose studies,or any consider-ations for the users objectives;and it is common practice toincrease or reduce significant digits of reported data to becommensurate with these considerations.It is beyond the scopeof these test methods to consider significant digits used inanalysis methods for engineering data.1.5 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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.6 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.2.Referenced Documents2.1 ASTM Standards:3C670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsD653 Terminology Relating to Soil,Rock,and ContainedFluidsD1193 Specification for Reagent WaterD2487 Practice for Classification of Soils for EngineeringPurposes(Unified Soil Classification System)D2488 Practice for Description and Identification of Soils(Visual-Manual Procedures)D3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection of Soil and Rock as1These test methods are under the jurisdiction ofASTM Committee D18 on Soiland Rock and is the direct responsibility of Subcommittee D18.22 on Media forPlant Growth.Current edition approved May 1,2019.Published May 2019.Originallyapproved in 1989.Last previous edition approved in 2018 as D4972 18.DOI:10.1520/D4972-19.2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.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.*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 StatesThis international standard was developed in accordance with internationally recognized principles