1、Designation: D4972 01 (Reapproved 2007)D4972 13Standard Test Method 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 pa
2、rentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope Scope*1.1 This test method covers the measurement of the pH of soils for uses other than for corrosion testing. Such measurementsare used in the agric
3、ultural, environmental, and natural resources fields. This measurement determines the degree of acidity oralkalinity in soil materials suspended in water and a 0.01 M calcium chloride solution. Measurements in both liquids are necessaryto fully define the soils pH. This variable is useful in determi
4、ning the solubility of soil minerals and the mobility of ions in thesoil and assessing the viability of the soil-plant environment. A more detailed discussion of the usefulness of this parameter is notwarranted here; however, it can be found in many discussions of the subject. A few such discussions
5、 are given as Refs (1-6)2 atthe end of the text.1.2 The values givenstated in SI units are to be regarded as the standard. No other units of measurement are included in thisstandard.1.3 All measured and calculated values shall conform to the guidelines for significant digits and rounding established
6、 in PracticeD6026.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use
7、.2. Referenced Documents2.1 ASTM Standards:3C670 Practice for Preparing Precision and Bias Statements for Test Methods for Construction MaterialsD653 Terminology Relating to Soil, Rock, and Contained FluidsD1193 Specification for Reagent WaterD3740 Practice for Minimum Requirements for Agencies Enga
8、ged in Testing and/or Inspection of Soil and Rock as Used inEngineering Design and ConstructionD6026 Practice for Using Significant Digits in Geotechnical DataG51 Test Method for Measuring pH of Soil for Use in Corrosion Testing3. Terminology3.1 Definitions:3.1.1 For common definitions of terms used
9、 in this standard, refer to Terminology D653.4. Summary of Test Method4.1 Measurement of the pH of soils in both suspensions of water and a calcium chloride solution are made with either apotentiometer using a pH sensitive electrode system (MethodA), or pH sensitive paper (Method B).The potentiomete
10、r is calibratedwith buffer solutions of known pH. The pH sensitive paper is a less accurate measurement and should only be used for a roughestimate of the soil pH. The electrode must be used for this measurement unless the pH sensitive paper is specified.NOTE 1The quality of the result produced by t
11、his standard is dependent on the competence of the personnel performing it, and the suitability of the1 This test method is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.22 on Soil as a Medium forPlant Growth.Current edition approv
12、ed Sept. 1, 2007Nov. 1, 2013. Published October 2007November 2013. Originally approved in 1989. Last previous edition approved in 20012007as D4972 01.D4972 01 (2007). DOI: 10.1520/D4972-01R07.10.1520/D4972-13.2 The boldface numbers in parentheses refer to a list of references at the end of the test
13、method.this standard.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard an
14、d is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only
15、the current versionof the standard as published by ASTM is to be considered the official document.*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 States1equipment and facilitie
16、s used. Agencies that meet the criteria of Practice D3740 are generally considered capable of competent and objectivetesting/sampling/inspection and the like. Users of this standard are cautioned that compliance with Practice D3740 does not in itself assure reliable results.Reliable results depend o
17、n many factors; Practice D3740 provides a means of evaluating some of those factors.5. Significance and Use5.1 The pH of the soil is a useful variable in determining the solubility of soil minerals and the mobility of ions in the soil andassessing the viability of the soil-plant environment.5.2 pH m
18、easurements are made in both water and a calcium chloride solution because the calcium displaces some of theexchangeable aluminum. The low ionic strength counters the dilution effect on the exchange equilibrium by setting the saltconcentration of the solution closer to that expected in the soil solu
19、tion. The pH values obtained in the solution of calcium chlorideare slightly lower than those measured in water due to the release of more aluminum ions which then hydrolyses. Therefore, bothmeasurements are required to fully define the character of the soils pH.5.3 For the purpose of this test meth
20、od the test soil must be sieved through a No. 10 sieve (2 mm sieve mesh openings). 2-mm(No. 10) sieve. Measurements on soils or soil fractions having particle sizes larger than 2 mm by this test method may be invalid.If soil or soil fractions with particles larger than 2 mm are used, it must be stat
21、ed in the report since the results may be significantlydifferent.5.4 All water used for this test method must be ASTM Type III or better. Type III water is defined by Specification D1193. Itis prepared by distillation, ion exchange, reverse osmosis, or a combination thereof.6. Interferences6.1 This
22、test method as measured by a pH probe has possible interferences due to a suspension effect or sedimentation potential.Users interested in a detailed discussion of the mechanism of this effect can find it in Refs (5) and (6).6.2 This effect is the main reason Test Method G51 can not be used for gene
23、ral measurement of pH outside of that for corrosionanalysis. Test Method G51 measures pH (an aqueous parameter) without adding any aqueous phase to the soil. This results inexcessive soil particle-pH probe contact that overestimates the activity of the hydrogen ions in solution and is thereforeunacc
24、eptable for general soil analysis.6.3 The suspension effect can be mitigated by careful attention to 10.1.7. Apparatus7.1 Method A, pH MeterPotentiometer equipped with glass-calomelan electrode system. Follow the manufacturersinstructions for the pH meter used. A silver/silver chloride electrode sys
25、tem or similar is also acceptable.7.2 Method B, pH PaperpH paper sensitive to a pH range from 1 to 12, with resolution to the nearest 0.2 pH unit.8. Reagents8.1 Purity of ReagentsReagent grade chemicals should be used in all tests. Unless otherwise indicated, it is intended that allreagents should c
26、onform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, wheresuch specifications are available.4 Other grades may be used, provided it is first ascertained that the reagent is of sufficient purityto permit its use without lessening the accuracy of the d
27、etermination.8.2 Purity of WaterAll water used for this test method must be ASTM Type III or better. Type III water is defined bySpecification D1193. It is prepared by distillation, ion exchange, reverse osmosis, or a combination thereof.8.3 Acid Potassium Phthalate Buffer Solution (0.05 M)Dissolve
28、10.21 g (dried 1 h at 105C) hour at 10565C) of potassiumphthalate in water and dilute to 1 L. The pH of this solution should be 4.0 at 20C. Protect the solution against evaporation andagainst contamination with molds. Replace the solution when mold is noticed. The effect of temperature is as follows
29、:C pH5 to 37 4.0This illustrates that the pH of the solution does not change over the range in temperature from 5 to 37C.8.4 Calcium Chloride Stock Solution (1.0 M)Dissolve 147 g of CaCl2 * 2H2O in water in a 1-L volumetric flask, cool, diluteto volume with water, and mix.8.5 Calcium Chloride Soluti
30、on (0.01 M)Dilute 20.0 mL of stock 1.0 M CaCl2 solution to 2 L with water. The pH of thissolution should be between 5 and 7.4 Reagent Chemicals, American Chemical Society Specifications , American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed bythe American
31、Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and NationalFormulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.D4972 1328.6 Phosphate Buffer Solution (0.025 M)Dissolve 3.40 g of KH2PO4 and 3.55 g of
32、 KH2HPO4 in water and dilute to 1 L. Drysalts 2 h at 130C before use. The pH of this solution should be 6.9 at 20C. The effect of temperature is as follows:C pH0 7.010 6.920 6.930 6.840 6.88.7 Carbonate Buffer Solution (0.025 M)Dissolve 2.10 g of NaHCO3 and 2.65 g of Na2CO3 in water and dilute to 1
33、L. Drysalts 2 hours at 130C before use. The pH of this solution should be 10.1 at 20C. The effect of temperature is as follows:C pH0 10.310 10.220 10.130 10.040 9.99. Calibration of pH Meter9.1 Calibrate the pH meter using the acid potassium phthalate and phosphatebuffer solutions in Section 8 buffe
34、r solutions. orother NIST traceable purchased buffers. Select buffers so that the expected pH value of the tested soil is bracketed. Adjustmentof the pH meter should follow the manufacturersmanufacturers direction.10. Procedure10.1 When making measurements with the pH electrode, place the electrode
35、into the partially settled suspension to mitigate thesuspension effect.10.2 For both methods, begin with an air dried soil that has been sieved through a No. 10 sieve (2 mm holes) 2-mm (No. 10)sieve to remove the coarser soil fraction.Air drying the soil is necessary to accomplish sieving and to con
36、trol the amount of waterpresent at the time of measurement.NOTE 2Some laboratories have reported that 10 ml of water and 10 g of soil is insufficient material to fully submerge the pH electrode on theirequipment. In these cases, a larger sample such as 40 ml of water and 40 g of soil is permitted10.
37、3 pH in Distilled WaterFor both methods, weigh out approximately 10 g of air dried soil. Place the soil into a glasscontainer and add approximately 10 mL of water. Mix thoroughly and let stand for 1 h.10.4 Method ARead pH on pH meter.10.5 Method BRead pH on pH paper.10.6 pH in 0.01 M Calcium Chlorid
38、e SolutionFor both methods weigh out approximately 10 g of air dried soil. Place the soilinto a glass container and add approximately 10 mL of the 0.01 M CaCl2 solution. Mix thoroughly and let stand for 1 h.10.7 Method ARead pH on pH meter.10.8 Method BRead pH on pH paper.10.9 The mixture should be
39、at approximately room temperature (15 to 25C) at the time of pH measurement.11. ReportReport:Test Data Sheet(s)/Form(s)11.1 Record as a minimum the following general information:11.1.1 Sample/specimen identifying information, such as Project No., Boring No., Sample No., Depth, etc.11.1.2 Any special
40、 selection and preparation process, such as removal of gravel or other materials.11.1.3 Technician name, method used and date.11.2 Report the pH of the soil to the first decimal place. Specify which of the pH measurements is in water and which is in thecalcium chloride solution.Also specify whether
41、the determinations were made with MethodAor Method B. If size fractions otherthan sieved through the No. 10 sieve are used, it must be stated in the report since the results may be significantly different.Recordas a minimum the following test information:11.2.1 Report the pH of the soil to the first
42、 decimal place11.2.2 Specify which of the pH measurements is in water and which is in the calcium chloride solution.11.2.3 Specify whether the determinations were made with Method A or Method B.11.2.4 Record if size fractions other than sieved through the 2 mm (No. 10) sieve are used, it must be sta
43、ted in the report sincethe results may be significantly different.12. Precision and Bias12.1 Precision:D4972 13312.1.1 Within-Laboratory PrecisionThe within laboratory standard deviations for MethodAare 0.031 (pH units) for the watermixture and 0.1395 (pH units) for the calcium chloride mixture. The
44、refore, results of two properly conducted tests in the same ordifferent laboratories should not differ by more than 0.0655 (pH units) for the water mixture and 0.389 pH units for the calciumchloride mixture. The within-laboratory standard deviations for Method B are 0.189 (pH units) for the water mi
45、xture and 0.2125(pH units) for the calcium chloride mixture. Therefore, results of two properly conducted tests in the same or different laboratoriesshould not differ by more than 0.535 (pH units) for the water mixture and 0.60 pH units for the calcium chloride mixture.12.1.1.1 The precision of Meth
46、odApresented was determined by the NationalTechnical Center of the United States Departmentof Agriculture. In their evaluation they used 174 replicates for the water mixture and 32 replicates in testing the calcium chloridemixture.12.1.1.2 The precision of Method B presented was determined by the Un
47、ited States Army Environmental Hygiene Agency. Intheir evaluation they used 25 replicates in testing each mixture.12.1.2 Between-Laboratory PrecisionThe between-laboratory standard deviation has not been determined for either method.Subcommittee D18.22 is actively seeking data to evaluate the betwee
48、n laboratory precision of this test method.12.2 BiasThere is no accepted reference value for this test method; 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 Co
49、oper, San Francisco, CA, 1965.(2) Greenland, D. J., and Hayes, M. H. B., The Chemistry of Soil Processes, 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 Potential 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.SUMMARY OF CHANGESCommittee
