ASTM D1067-92(1996)
(Test Method)Standard Test Methods for Acidity or Alkalinity of Water
Standard Test Methods for Acidity or Alkalinity of Water
SCOPE
1.1 These test methods cover the determination of acidity or alkalinity of all types of water. Three test methods are given as follows: SectionsTest Method A (Electrometric Titration) 7 to 15Test Method B (Electrometric or Color-Change Titration) 16 to 24Test Method C (Color-Change Titration After HydrogenPeroxide Oxidation and Boiling) 25 to 33
1.2 In all of these test methods the hydrogen or hydroxyl ions present in water by virtue of the dissociation or hydrolysis of its solutes, or both, are neutralized by titration with standard alkali (acidity) or acid (alkalinity). Of the three procedures, Test Method A is the most precise and accurate. It is used to develop an electrometric titration curve (sometimes referred to as a pH curve), which defines the acidity or alkalinity of the sample and indicates inflection points and buffering capacity, if any. In addition, the acidity or alkalinity can be determined with respect to any pH of particular interest. The other two methods are used to determine acidity or alkalinity relative to a predesignated end point based on the change in color of an internal indicator or the equivalent end point measured by a pH meter. They are suitable for routine control purposes.
1.3 When titrating to a specific end point, the choice of end point will require a careful analysis of the titration curve, the effects of any anticipated changes in composition on the titration curve, knowledge of the intended uses or disposition of the water, and a knowledge of the characteristics of the process controls involved. While inflection points (rapid changes in pH) are usually preferred for accurate analysis of sample composition and obtaining the best precision, the use of an inflection point for process control may result in significant errors in chemical treatment or process control in some applications. When titrating to a selected end point dictated by practical considerations, (1) only a part of the actual neutralizing capacity of the water may be measured, or (2) this capacity may actually be exceeded in arriving at optimum acidity or alkalinity conditions.
1.4 A scope section is provided in each test method as a guide. It is the responsibility of the analyst to determine the acceptability of these test methods for each matrix.
1.5 Former Test Methods C (Color-Comparison Titration) and D (Color-Change Titration After Boiling) were discontinued. Refer to for historical information.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or
withdrawn. Contact ASTM International (www.astm.org) for the latest information.
Designation: D 1067 – 92 (Reapproved 1996)
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Test Methods for
Acidity or Alkalinity of Water
This standard is issued under the fixed designation D 1067; 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.
This standard has been approved for use by agencies of the Department of Defense. Consult the DoD Index of Specifications and
Standards for the specific year of issue which has been adopted by the Department of Defense.
1. Scope * izing capacity of the water may be measured, or (2) this
capacity may actually be exceeded in arriving at optimum
1.1 These test methods cover the determination of acidity
acidity or alkalinity conditions.
or alkalinity of all types of water. Three test methods are given
1.4 A scope section is provided in each test method as a
as follows:
guide. It is the responsibility of the analyst to determine the
Sections
acceptability of these test methods for each matrix.
Test Method A (Electrometric Titration) 7 to 15
Test Method B (Electrometric or Color-Change Titration) 16 to 24
1.5 Former Test Methods C (Color-Comparison Titration)
Test Method C (Color-Change Titration After Hydrogen 25 to 33
and D (Color-Change Titration After Boiling) were discontin-
Peroxide Oxidation and Boiling)
ued. Refer to Appendix X4 for historical information.
1.2 In all of these test methods the hydrogen or hydroxyl
1.6 This standard does not purport to address all of the
ions present in water by virtue of the dissociation or hydrolysis
safety concerns, if any, associated with its use. It is the
of its solutes, or both, are neutralized by titration with standard
responsibility of the user of this standard to establish appro-
alkali (acidity) or acid (alkalinity). Of the three procedures,
priate safety and health practices and determine the applica-
Test Method A is the most precise and accurate. It is used to
bility of regulatory limitations prior to use.
develop an electrometric titration curve (sometimes referred to
2. Referenced Documents
as a pH curve), which defines the acidity or alkalinity of the
sample and indicates inflection points and buffering capacity, if 2.1 ASTM Standards:
any. In addition, the acidity or alkalinity can be determined D 596 Practice for Reporting Results of Analysis of Water
with respect to any pH of particular interest. The other two D 1129 Terminology Relating to Water
methods are used to determine acidity or alkalinity relative to D 1192 Specification for Equipment for Sampling Water
a predesignated end point based on the change in color of an and Steam in Closed Conduits
internal indicator or the equivalent end point measured by a pH D 1193 Specification for Reagent Water
meter. They are suitable for routine control purposes. D 1293 Test Methods for pH of Water
1.3 When titrating to a specific end point, the choice of end D 2777 Practice for Determination of Precision and Bias of
Applicable Methods of Committee D-19 on Water
point will require a careful analysis of the titration curve, the
effects of any anticipated changes in composition on the D 3370 Practices for Sampling Water from Closed Con-
duits
titration curve, knowledge of the intended uses or disposition
of the water, and a knowledge of the characteristics of the E 200 Practice for Preparation, Standardization, and Stor-
age of Standard and Reagent Solutions for Chemical
process controls involved. While inflection points (rapid
Analysis
changes in pH) are usually preferred for accurate analysis of
sample composition and obtaining the best precision, the use of
3. Terminology
an inflection point for process control may result in significant
3.1 Definitions—The terms in these test methods are defined
errors in chemical treatment or process control in some
in accordance with Terminology D 1129.
applications. When titrating to a selected end point dictated by
3.1.1 Certain uses of terminology exist in the water treat-
practical considerations, (1) only a part of the actual neutral-
ment industry which may differ from these definitions. A
discussion of terms is presented in Appendix X1.
These test methods are under the jurisdiction of ASTM Committee D-19 on
4. Significance and Use
Water and are the responsibility of Subcommittee D19.05 on Inorganic Constituents
in Water.
4.1 Acidity and alkalinity measurements are used to assist in
Current edition approved May 15, 1992. Published September 1992. Originally
establishing levels of chemical treatment to control scale,
published as D 1067 – 49. Last previous edition D 1067 – 88.
The basic procedures used in these test methods have appeared widespread in
the technical literature for many years. Only the particular adaptation of the
electrometric titration appearing as the Referee Method is believed to be largely the Annual Book of ASTM Standards, Vol 11.01.
work of Committee D-19. Annual Book of ASTM Standards, Vol 15.05.
*A Summary of Changes section appears at the end of this standard.
D 1067
corrosion, and other adverse chemical equilibria. materials may not be removed to increase precision, because
4.2 Levels of acidity or alkalinity are critical in establishing some are an important component of the acid- or alkali-
solubilities of some metals, toxicity of some metals, and the consuming property of the sample. Similarly, the development
buffering capacity of some waters. of a precipitate during titration may make the glass electrode
sluggish and cause high results.
5. Purity of Reagents
10. Apparatus
5.1 Reagent grade chemicals shall be used in all tests.
Unless otherwise indicated, it is intended that all reagents shall
10.1 Electrometric pH Measurement Apparatus, conform-
conform to the specifications of the Committee on Analytical
ing to the requirements given in Test Methods D 1293.
Reagents of the American Chemical Society, where such
11. Reagents
specifications are available. Other grades may be used, pro-
vided it is first ascertained that the reagent is of sufficiently
11.1 Hydrochloric Acid, Standard (0.02 N) (see Note 1)—
high purity to permit its use without lessening the accuracy of
Prepare and standardize as directed in Practice E 200, except
the determination.
that the titration shall be made electrometrically. The inflection
5.2 Unless otherwise indicated, references to water shall be
point corresponding to the complete titration of carbonic acid
understood to mean reagent water conforming to Specification
salts will be very close to pH 3.9.
D 1193, Type I. In addition, reagent water for this test shall be
NOTE 1—Sulfuric acid of similar normality may be used instead of
free of carbon dioxide (CO ) and shall have a pH between 6.2
hydrochloric acid. Prepare and standardize in like manner.
and 7.2 at 25°C. A procedure for the preparation of carbon
11.2 Sodium Hydroxide, Standard (0.02 N)—Prepare and
dioxide-free water is given in Practice E 200.
standardize as directed in Practice E 200, except that the
6. Sampling
titration shall be made electrometrically. The inflection point
corresponding to the complete titration of the phthalic acid salt
6.1 Collect the sample in accordance with Specification
will be very close to pH 8.6.
D 1192 and Practices D 3370 as applicable.
6.2 The time interval between sampling and analysis shall
12. Procedure
be as short as practically possible in all cases. It is mandatory
12.1 Mount the glass and reference electrodes in two of the
that analyses by Test Method A be carried out the same day the
holes of a clean, threehole rubber stopper chosen to fit a
samples are taken; essentially immediate analysis is desirable
300-mL, tall-form Berzelius beaker without spout, or equiva-
for those waste waters containing hydrolyzable salts that
lent apparatus. Place the electrodes in the beaker and standard-
contain cations in several oxidation states.
ize the pH meter, using a reference buffer having a pH
TEST METHOD A—ELECTROMETRIC TITRATION
approximating that expected for the sample (see Test Methods
D 1293). Rinse the electrodes, first with reagent water, then
7. Scope
with a portion of the sample. Following the final rinse, drain
7.1 This test method is applicable to the determination of
the beaker and electrodes completely.
acidity or alkalinity of all waters that are free of constituents
12.2 Pipet 100 mL of the sample, adjusted, if necessary, to
that interfere with electrometric pH measurements. It is used
room temperature, into the beaker through the third hole in the
for the development of a titration curve that will define
stopper. Hold the tip of the pipet near the bottom of the beaker
inflection points and indicate buffering capacity, if any. The
while discharging the sample.
acidity or alkalinity of the water or that relative to a particular
12.3 Measure the pH of the sample in accordance with Test
pH is determined from the curve.
Methods D 1293.
12.4 Add either 0.02 N acid or alkali solution, as indicated,
8. Summary of Test Method
in increments of 0.5 mL or less (see Note 2). After each
8.1 To develop a titration curve that will properly identify
addition, mix the solution thoroughly. Determine the pH when
the inflection points, standard acid or alkali is added to the
the mixture has reached equilibrium as indicated by a constant
sample in small increments and a pH reading is taken after each
reading (see Note 3). Mechanical stirring, preferably of the
addition. The cumulative volume of solution added is plotted
magnetic type, is required for this operation; mixing by means
against the observed pH values. All pH measurements are
of a gas stream is not permitted. Continue the titration until the
made electrometrically.
necessary data for the titration curve have been obtained.
9. Interferences
NOTE 2—If the sample requires appreciably more than 25 mL of
standard solution for its titration, use a 0.1 N solution, prepared and
9.1 Although oily matter, soaps, suspended solids, and other
standardized in the same manner (see Practice E 200).
waste materials may interfere with the pH measurement, these
NOTE 3—An electrometric titration curve is smooth, with the pH
changing progressively in a single direction, if equilibrium is achieved
after each incremental addition of titrant, and may contain one or more
Reagent Chemicals, American Chemical Society Specifications, American
inflection points. Ragged or irregular curves may indicate that equilibrium
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
was not attained before adding succeeding increments. The time required
listed by the American Chemical Society, see Analar Standards for Laboratory
will vary with different waters as the reaction rate constants of different
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
chemical equilibria vary. In some instances the reaction time may be an
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
MD. interval of a few seconds while other slower, more complex reactions may
D 1067
require much longer intervals. It is important, therefore, that the period be
designated pH, the end point being determined
sufficient to allow for any significant pH changes, yet consistent with good
electrometrically or by the color change of an internal
laboratory practices.
indicator.
12.5 To develop a titration curve, plot the cumulative
18. Interferences
millilitres of standard solution added to the sample aliquot
18.1 Natural color or the formation of a precipitate while
against the observed pH values. The acidity or alkalinity
titrating the sample may mask the color change of an internal
relative to a particular pH may be determined from the curve.
indicator. Suspended solids may interfere in electrometric
13. Calculation
titrations by making the glass electrode sluggish. Waste
13.1 Calculate the acidity or alkalinity, in milliequivalents
materials present in some waters may interfere chemically with
per litre, using Eq. 1: color titrations by destroying the indicator. Variable results
may be experienced with waters containing oxidizing or
Acidity ~or alkalinity!, meq/L ~epm!5 AN 3 10 (1)
reducing substances, depending on the equilibrium conditions
where:
and the manner in which the sample is handled.
A 5 standard acid or alkali required for the titration, mL,
19. Apparatus
and
N 5 normality of the standard solution.
19.1 Electrometric pH Measurement Apparatus—See 10.1.
14. Report 20. Reagents
14.1 Report the results of titrations to specific end points as
20.1 Bromcresol Green Indicator Solution (l g/L)—
follows: “The acidity (or alkalinity) to pH at °C 5 meq/L
Dissolve 0.1 g of bromcresol green in 2.9 mL of 0.02 N sodium
(epm).”
hydroxide (NaOH) solution. Dilute to 100 mL with water.
14.2 Appropriate factors for converting milliequivalents per
20.2 Hydrochloric Acid, Standard (0.02 N) (Note 1)—See
litre (epm) to other units are given in Practice D 596.
11.1, except that the acid may be standardized by colorimetric
titration as directed in Practice E 200 when an indicator is used
15. Precision and Bias
for sample titration.
15.1 The precision and bias data presented in Table 1 for
20.3 Methyl Orange Indicator Solution (0.5 g/L)—
this test method meet the requirements of Practice D 2777.
Dissolve 0.05 g of methyl orange in water and dilute to 100
15.2 The collaborative test of this test method was
mL.
performed in reagent waters by six laboratories using one
20.4 Methyl Purple Indicator Solution (l g/L)—Dissolve
operator each, using three levels of concentration for both the
0.45 g of dimethyl-aminoazobenzene-O-carboxylic acid,
acidity and alkalinity.
sodium salt, in approximately 300 mL of water. To this solution
add 0.55 g of a water-soluble blue dye-stuff, Color Index No.
TEST METHOD B—ELECTROMETRIC OR
714, and dissolve. Dilute to 1 L with water. This indicator is
COLOR-CHANGE TITRATION
available commercially in prepared form.
16. Scope
20.5 Methyl Red Indicator Solution (1 g/L)—Dissolve 0.1 g
of water-soluble methyl red in water and dilute to 100 mL.
16.1 This test method covers the rapid, routine control
20.6 Phenolphthalein Indicator Solution (5 g/L)—
measurement of acidity or alkalinity to predesignated end
Dissolve 0.5 g of phenolphthalein in 50 mL of ethyl alcohol (95
points of waters that contain no materials that buffer at the end
%) and dilute to 100 mL with water.
po
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