1、Designation: D 4972 01 (Reapproved 2007)Standard Test Method forpH of Soils1This standard is issued under the fixed designation D 4972; 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 parenthe
2、ses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the measurement of the pH ofsoils for uses other than for corrosion testing. Such measure-ments are used in the agricultural, en
3、vironmental, and naturalresources fields. This measurement determines the degree ofacidity or alkalinity in soil materials suspended in water and a0.01 M calcium chloride solution. Measurements in bothliquids are necessary to fully define the soils pH. This variableis useful in determining the solub
4、ility of soil minerals and themobility of ions in the soil and assessing the viability of thesoil-plant environment. A more detailed discussion of theusefulness of this parameter is not warranted here; however, itcan be found in many discussions of the subject. A few suchdiscussions are given as Ref
5、s (1-6)2at the end of the text.1.2 The values given in SI units are to be regarded as thestandard.1.3 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
6、 practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:3C 670 Practice for Preparing Precision and Bias Statementsfor Test Methods for Construction MaterialsD 653 Terminology Relating to Soil, Rock, and ContainedFluidsD 1193 Speci
7、fication for Reagent WaterD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering Design and ConstructionG51 Test Method for Measuring pH of Soil for Use inCorrosion Testing3. Terminology3.1 Definitions:3.1.1 For common def
8、initions of terms used in this standard,refer to Terminology D 653.4. Summary of Test Method4.1 Measurement of the pH of soils in both suspensions ofwater and a calcium chloride solution are made with either apotentiometer using a pH sensitive electrode system (MethodA), or pH sensitive paper (Metho
9、d B). The potentiometer iscalibrated with buffer solutions of known pH. The pH sensitivepaper is a less accurate measurement and should only be usedfor a rough estimate of the soil pH. The electrode must be usedfor this measurement unless the pH sensitive paper is specified.5. Significance and Use5.
10、1 The pH of the soil is a useful variable in determining thesolubility of soil minerals and the mobility of ions in the soiland assessing the viability of the soil-plant environment.5.2 pH measurements are made in both water and a calciumchloride solution because the calcium displaces some of theexc
11、hangeable aluminum. The low ionic strength counters thedilution effect on the exchange equilibrium by setting the saltconcentration of the solution closer to that expected in the soilsolution. The pH values obtained in the solution of calciumchloride are slightly lower than those measured in water d
12、ue tothe release of more aluminum ions which then hydrolyses.Therefore, both measurements are required to fully define thecharacter of the soils pH.5.3 For the purpose of this test method the test soil must besieved through a No. 10 sieve (2 mm sieve mesh openings).Measurements on soils or soil frac
13、tions having particle sizeslarger than 2 mm by this test method may be invalid. If soil or1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.22 on Soil as a Mediumfor Plant Growth.Current edition approved Sept. 1, 200
14、7. Published October 2007. Originallyapproved in 1989. Last previous edition approved in 2001 as D 4972 01.2The boldface numbers in parentheses refer to a list of references at the end ofthe test method.3For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Ser
15、vice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.soil fractions with particles larger than 2
16、 mm are used, it mustbe stated in the report since the results may be significantlydifferent.5.4 All water used for this test method must be ASTM TypeIII or better. Type III water is defined by Specification D 1193.It is prepared by distillation, ion exchange, reverse osmosis, ora combination thereo
17、f.6. Interferences6.1 This test method as measured by a pH probe haspossible interferences due to a suspension effect or sedimen-tation potential. Users interested in a detailed discussion of themechanism of this effect can find it in Refs (5) and (6).6.2 This effect is the main reason Test Method G
18、51can notbe used for general measurement of pH outside of that forcorrosion analysis. Test Method G51measures pH (an aque-ous parameter) without adding any aqueous phase to the soil.This results in excessive soil particle-pH probe contact thatoverestimates the activity of the hydrogen ions in soluti
19、on andis therefore unacceptable for general soil analysis.6.3 The suspension effect can be mitigated by carefulattention to 10.1.7. Apparatus7.1 Method A, pH MeterPotentiometer equipped withglass-calomel electrode system. Follow the manufacturersinstructions for the pH meter used. A silver/silver ch
20、lorideelectrode system or similar is also acceptable.7.2 Method B, pH PaperpH paper sensitive to a pH rangefrom 1 to 12, with resolution to the nearest 0.2 pH unit.8. Reagents8.1 Purity of ReagentsReagent grade chemicals should beused in all tests. Unless otherwise indicated, it is intended thatall
21、reagents should conform to the specifications of theCommittee on Analytical Reagents of the American ChemicalSociety, where such specifications are available.4Other gradesmay be used, provided it is first ascertained that the reagent isof sufficient purity to permit its use without lessening theaccu
22、racy of the determination.8.2 Purity of WaterAll water used for this test methodmust be ASTM Type III or better. Type III water is defined bySpecification D 1193. It is prepared by distillation, ion ex-change, reverse osmosis, or a combination thereof.8.3 Acid Potassium Phthalate Buffer Solution (0.
23、05 M)Dissolve 10.21 g (dried1hat105C) of potassium phthalate inwater and dilute to 1 L. The pH of this solution should be 4.0at 20C. Protect the solution against evaporation and againstcontamination with molds. Replace the solution when mold isnoticed. The effect of temperature is as follows:C pH5to
24、37 4.0This illustrates that the pH of the solution does not changeover the range in temperature from 5 to 37C.8.4 Calcium Chloride Stock Solution (1.0 M)Dissolve147 g of CaCl2*2H2O in water in a 1-L volumetric flask, cool,dilute to volume with water, and mix.8.5 Calcium Chloride Solution (0.01 M)Dil
25、ute 20.0 mLof stock 1.0 M CaCl2solution to 2 L with water. The pH of thissolution should be between 5 and 7.8.6 Phosphate Buffer Solution (0.025 M)Dissolve 3.40 gof KH2PO4and 3.55 g of KH2HPO4in water and dilute to 1L. Dry salts2hat130C before use. The pH of this solutionshould be 6.9 at 20C. The ef
26、fect of temperature is as follows:C pH07.010 6.920 6.930 6.840 6.89. Calibration of pH Meter9.1 Calibrate the pH meter using the acid potassium phtha-late and phosphate buffer solutions. Adjustment of the pHmeter should follow the manufacturers direction.10. Procedure10.1 When making measurements wi
27、th the pH electrode,place the electrode into the partially settled suspension tomitigate the suspension effect.10.2 For both methods, begin with an air dried soil that hasbeen sieved through a No. 10 sieve (2 mm holes) to remove thecoarser soil fraction. Air drying the soil is necessary toaccomplish
28、 sieving and to control the amount of water presentat the time of measurement.10.3 pH in Distilled WaterFor both methods, weigh outapproximately 10 g of air dried soil. Place the soil into a glasscontainer and add approximately 10 mL of water. Mix thor-oughly and let stand for 1 h.10.4 Method ARead
29、pH on pH meter.10.5 Method BRead pH on pH paper.10.6 pH in 0.01 M Calcium Chloride SolutionFor bothmethods weigh out approximately 10 g of air dried soil. Placethe soil into a glass container and add approximately 10 mL ofthe 0.01 M CaCl2solution. Mix thoroughly and let stand for 1h.10.7 Method ARea
30、d pH on pH meter.10.8 Method BRead pH on pH paper.10.9 The mixture should be at approximately room tempera-ture (15 to 25C) at the time of pH measurement.11. Report11.1 Report the pH of the soil to the first decimal place.Specify which of the pH measurements is in water and whichis in the calcium ch
31、loride solution. Also specify whether thedeterminations were made with Method A or Method B. If sizefractions other than sieved through the No. 10 sieve are used,it must be stated in the report since the results may besignificantly different.12. Precision and Bias12.1 Precision:4Reagent Chemicals, A
32、merican Chemical Society Specifications, AmericanChemical Society, Washington, DC. For suggestions on the testing of reagents notlisted by the American Chemical Society, see Analar Standards for LaboratoryChemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeiaand National Formul
33、ary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,MD.D 4972 01 (2007)212.1.1 Within-Laboratory PrecisionThe within laboratorystandard deviations for Method A are 0.031 (pH units) for thewater mixture and 0.1395(pH units) for the calcium chloridemixture. Therefore, results of two properly c
34、onducted tests inthe same or different laboratories should not differ by morethan 0.0655(pH units) for the water mixture and 0.389 pH unitsfor the calcium chloride mixture. The within-laboratory stan-dard deviations for Method B are 0.189 (pH units) for the watermixture and 0.2125(pH units) for the
35、calcium chloride mixture.Therefore, results of two properly conducted tests in the sameor different laboratories should not differ by more than 0.535(pH units) for the water mixture and 0.60 pH units for thecalcium chloride mixture.12.1.1.1 The precision of Method A presented was deter-mined by the
36、National Technical Center of the United StatesDepartment of Agriculture. In their evaluation they used 174replicates for the water mixture and 32 replicates in testing thecalcium chloride mixture.12.1.1.2 The precision of Method B presented was deter-mined by the United States Army Environmental Hyg
37、ieneAgency. In their evaluation they used 25 replicates in testingeach mixture.12.1.2 Between-Laboratory PrecisionThe between-laboratory standard deviation has not been determined foreither method. Subcommittee D18.22 is actively seeking datato evaluate the between laboratory precision of this testm
38、ethod.12.2 BiasThere is no accepted reference value for this testmethod; therefore, bias cannot be determined.13. Keywords13.1 acidity; alkalinity; pH; reaction; soilREFERENCES(1) Garrels, R. M., and Christ, C. L., Solutions, Minerals, and Equilibria,Freeman Cooper, San Francisco, CA, 1965.(2) Green
39、land, D. J., and Hayes, M. H. B., The Chemistry of SoilProcesses, Wiley, New York, NY, 1981.(3) Sposito, G., The Thermodynamics of Soil Solutions, Clarendon,Oxford, United Kindom, 1981.(4) Davies, J. T., and Rideal, E. K., Interfacial Phenomena, Academic,New York, NY, 1963.(5) Hunter, R. J., Zeta Po
40、tential in Colloid Science,Academic, New York,NY, 1981.(6) Perrin, D. D., and Dempsey, B., Buffers for pH and Metal Ion Control,Chapman and Hall, London, United Kindom, 1974.ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mention
41、edin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and
42、 must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of
43、 theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box
44、C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).5These data satisfy the 1S and D2S requirements outlined in Practice C 670.D 4972 01 (2007)3
