ASTM D4972-01

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Designation:D4972–01
Standard Test Method for
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pH of Soils
This standard is issued under the fixed designation D 4972; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
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1. Scope * as Used in Engineering Design and Construction
G 51 Test Method for pH of Soil for Use in Corrosion
1.1 This test method covers the measurement of the pH of
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Testing
soils for uses other than for corrosion testing. Such measure-
ments are used in the agricultural, environmental, and natural
3. Terminology
resources fields. This measurement determines the degree of
3.1 Definitions:
acidity or alkalinity in soil materials suspended in water and a
3.1.1 For common definitions of terms used in this standard,
0.01 M calcium chloride solution. Measurements in both
refer to Terminology D 653.
liquids are necessary to fully define the soil’s pH.This variable
is useful in determining the solubility of soil minerals and the
4. Summary of Test Method
mobility of ions in the soil and assessing the viability of the
4.1 Measurement of the pH of soils in both suspensions of
soil-plant environment. A more detailed discussion of the
water and a calcium chloride solution are made with either a
usefulness of this parameter is not warranted here; however, it
potentiometer using a pH sensitive electrode system (Method
can be found in many discussions of the subject. A few such
2 A), or pH sensitive paper (Method B). The potentiometer is
discussions are given as Refs (1-6) at the end of the text.
calibrated with buffer solutions of known pH.The pH sensitive
1.2 The values given in SI units are to be regarded as the
paper is a less accurate measurement and should only be used
standard.
for a rough estimate of the soil pH.The electrode must be used
1.3 This standard does not purport to address all of the
for this measurement unless the pH sensitive paper is specified.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
5. Significance and Use
priate safety and health practices and determine the applica-
5.1 The pH of the soil is a useful variable in determining the
bility of regulatory limitations prior to use.
solubility of soil minerals and the mobility of ions in the soil
and assessing the viability of the soil-plant environment.
2. Referenced Documents
5.2 pH measurements are made in both water and a calcium
2.1 ASTM Standards:
chloride solution because the calcium displaces some of the
C 670 Practice for Preparing Precision and Bias Statements
exchangeable aluminum. The low ionic strength counters the
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for Test Methods for Construction Materials
dilution effect on the exchange equilibrium by setting the salt
D 653 Terminology Relating to Soil, Rock, and Contained
concentration of the solution closer to that expected in the soil
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Fluids
5 solution. The pH values obtained in the solution of calcium
D 1193 Specification for Reagent Water
chloride are slightly lower than those measured in water due to
D 3740 Practice for Minimum Requirements for Agencies
the release of more aluminum ions which then hydrolyses.
Engaged in the Testing and/or Inspection of Soil and Rock
Therefore, both measurements are required to fully define the
character of the soil’s pH.
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5.3 For the purpose of this test method the test soil must be
ThistestmethodisunderthejurisdictionofASTMCommitteeD18onSoiland
Rock and is the direct responsibility of Subcommittee D18.22 on Soil as a Medium
sieved through a No. 10 sieve (2 mm sieve mesh openings).
for Plant Growth.
Measurements on soils or soil fractions having particle sizes
Current edition approved Jan. 10, 2001. Published February 2001. Originally
larger than 2 mm by this test method may be invalid. If soil or
published as D 4972 – 89. Last previous edition D 4972 – 95a.
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The boldface numbers in parentheses refer to a list of references at the end of
the test method.
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Annual Book of ASTM Standards, Vol 04.02.
4 6
Annual Book of ASTM Standards, Vol 04.09. Annual Book of ASTM Standards, Vol 04.08.
5 7
Annual Book of ASTM Standards, Vol 11.01. Annual Book of ASTM Standards, Vol 03.02.
*A Summary of Changes section appears at the end of this standard.
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D4972
soil fractions with particles larger than 2 mm are used, it must This illustrates that the pH of the solution does not change
be stated in the report since the results may be significantly over the range in temperature from 5 to 37
...