ASTM D1253-14(2021)e1
(Test Method)Standard Test Method for Residual Chlorine in Water
Standard Test Method for Residual Chlorine in Water
SIGNIFICANCE AND USE
5.1 Chlorine is used to destroy or deactivate a variety of unwanted chemicals and microorganisms in water and wastewater.
5.2 An uncontrolled excess of chlorine in water, whether free available or combined, can adversely affect the subsequent use of the water.
SCOPE
1.1 This test method covers the determination of residual chlorine in water by direct amperometric titration.
1.2 Within the constraints specified in Section 6, this test method is not subject to commonly encountered interferences and is applicable to most waters. Some waters, however, can exert an iodine demand, usually because of organic material, making less iodine available for measurement by this test method. Thus, it is possible to obtain falsely low chlorine readings, even though the test method is working properly, without the user's knowledge.
1.3 Precision data for this test method were obtained on estuary, inland main stem river, fresh lake, open ocean, and fresh cooling tower blowdown water. Bias data could not be determined because of the instability of solutions of chlorine in water. It is the user's responsibility to ensure the validity of the test method for untested types of water.
1.4 In the testing by which this standard was validated, the direct and back starch-iodide titrations and the amperometric back titration, formerly part of this standard, were found to be unworkable and were discontinued in 1986. Historical information is presented in Appendix X1.
Note 1: Orthotolidine test methods have been omitted because of poor precision and accuracy.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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Designation: D1253 − 14 (Reapproved 2021)
Standard Test Method for
Residual Chlorine in Water
This standard is issued under the fixed designation D1253; 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 (´) indicates an editorial change since the last revision or reapproval.
ε NOTE—The WTO caveat was added editorially in December 2021.
1. Scope ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.1 This test method covers the determination of residual
mendations issued by the World Trade Organization Technical
chlorine in water by direct amperometric titration.
Barriers to Trade (TBT) Committee.
1.2 Within the constraints specified in Section 6, this test
2. Referenced Documents
method is not subject to commonly encountered interferences
and is applicable to most waters. Some waters, however, can
2.1 ASTM Standards:
exert an iodine demand, usually because of organic material,
D1129 Terminology Relating to Water
making less iodine available for measurement by this test
D1193 Specification for Reagent Water
method. Thus, it is possible to obtain falsely low chlorine
D2777 Practice for Determination of Precision and Bias of
readings, even though the test method is working properly,
Applicable Test Methods of Committee D19 on Water
without the user’s knowledge.
D3370 Practices for Sampling Water from Flowing Process
Streams
1.3 Precision data for this test method were obtained on
D5847 Practice for Writing Quality Control Specifications
estuary, inland main stem river, fresh lake, open ocean, and
for Standard Test Methods for Water Analysis
fresh cooling tower blowdown water. Bias data could not be
determinedbecauseoftheinstabilityofsolutionsofchlorinein
3. Terminology
water. It is the user’s responsibility to ensure the validity of the
3.1 Definitions—For definitions of terms used in this test
test method for untested types of water.
method, refer to Terminology D1129.
1.4 In the testing by which this standard was validated, the
3.2 Definitions of Terms Specific to This Standard:
direct and back starch-iodide titrations and the amperometric
3.2.1 combined residual chlorine, n—residual consisting of
back titration, formerly part of this standard, were found to be
chlorine combined with ammonia nitrogen or nitrogenous
unworkable and were discontinued in 1986. Historical infor-
compounds.
mation is presented in Appendix X1.
3.2.2 free-available-chlorine residual, n—residual consist-
NOTE1—Orthotolidinetestmethodshavebeenomittedbecauseofpoor
ing of hypochlorite ions, hypochlorous acid, or a combination
precision and accuracy.
thereof.
1.5 The values stated in SI units are to be regarded as
3.2.3 total residual chlorine (chlorine residual), n—the
standard. No other units of measurement are included in this
amount of available chlorine-induced oxidants present in water
standard.
at any specified period, subsequent to the addition of chlorine.
1.6 This standard does not purport to address all of the
3.2.3.1 Discussion—Chlorine present as chloride is neither
safety concerns, if any, associated with its use. It is the
included in these terms nor determined by this test method.
responsibility of the user of this standard to establish appro-
Bromine, bromine combined with ammonia or nitrogenous
priate safety, health, and environmental practices and deter-
compounds, and chlorine dioxide are not distinguished by this
mine the applicability of regulatory limitations prior to use.
test method from the corresponding chlorine compounds.
1.7 This international standard was developed in accor-
4. Summary of Test Method
dance with internationally recognized principles on standard-
4.1 This is an amperometric titration test method utilizing
phenylarsine oxide as the titrant. When the titrator cell is
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
in Water. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Nov. 1, 2021. Published December 2021. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1953. Last previous edition approved in 2014 as D1253 – 14. DOI: Standards volume information, refer to the standard’s Document Summary page on
10.1520/D1253-14R21E01. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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D1253 − 14 (2021)
immersedinasamplecontainingchlorine,currentisgenerated. 7. Apparatus
As phenylarsine oxide is added, the chlorine is reduced and the 3
7.1 Amperometric Titration Apparatus —Amperometric
generation of current ceases. When chlorine is present as a
titration apparatus are available utilizing analog or digital
chloramine, potassium iodide is added, releasing iodine, which
displays. An instrument employing a digital display is pre-
is titrated in a similar manner. The iodine content is calculated
ferred as it will provide better discrimination of current change
in terms of free chlorine.
vs titrant volume addition and the graphical endpoint determi-
nation of the test than will an instrument with an analog
5. Significance and Use
display. See 10.3.2.
5.1 Chlorine is used to destroy or deactivate a variety of
NOTE 2—When the titrator has been out of service for a day or more,
unwanted chemicals and microorganisms in water and waste- check the electrode for sensitivity by noting the rapidity of the pointer
deflection or the instruments response. If the pointer or instrument display
water.
responds slowly after the addition of KI solution, add a small amount of
biiodate. If it responds slowly to free available chlorine, sensitize it by
5.2 An uncontrolled excess of chlorine in water, whether
adding chlorine. Refer to the manufacturers’ manual for detailed instruc-
freeavailableorcombined,canadverselyaffectthesubsequent
tions for cleaning and condition the electrode(s) as well as instrument
use of the water.
calibration.
7.2 Glassware—Use glass sample containers which have
6. Interferences
been conditioned to eliminate chlorine demands. Condition
6.1 This test method is not subject to interferences from
with water containing at least 10 mg/L of residual chlorine for
temperature, color, or turbidity of sample. at least 2 h prior to use and then rinse thoroughly.
6.2 ValuesofpHabove8.0interferebyslowingthereaction
8. Reagents and Materials
rate. Buffering the sample to pH 7.0 or less eliminates the
8.1 Purity of Reagents—Reagent grade chemicals shall be
interference.
used in all tests. Unless otherwise indicated, it is intended that
all reagents shall conform to the specifications of the Commit-
6.3 Erratic behavior of the apparatus in the presence of
teeonAnalyticalReagentsoftheAmericanChemicalSociety.
cupric ions has been reported.
Other grades may be used, provided it is first ascertained that
6.4 Cuprous and silver ions tend to poison the electrode of
the reagent is of sufficiently high purity to permit its use
the titrator.
without lessening the accuracy of the determination.
6.5 Nitrogen trichloride and some N-chloro compounds are
8.2 Purity of Water—Unless otherwise indicated, references
often present as products of the chlorination of wastewaters
towatershallbeunderstoodtomeanreagentwaterconforming
and will titrate partially as free available chlorine and partially
to Specification D1193, Type III, further treated to be free of
as combined residual chlorine. This error can be avoided only
chlorine demand. Other reagent water types (Type I) may be
in the determination of total residual chlorine.
used provided it is first ascertained that the water is of
sufficiently high purity to permit its use without adversely
6.6 Exposure to high concentrations of free available chlo-
affecting the bias and precision of the test method. Type III
rine causes a film-type polarization that reverses very slowly.
water was specified at the time of round robin testing of this
This can be avoided by diluting the sample with water to less
method. A suggested method for preparation of chlorine
than 10 mg/L of free available chlorine.
demand-free water is to add approximately 20 mg/L of
6.7 If chlorine dioxide is present, an unknown portion
available chlorine to Type III water, let it stand for about a
titratesasfreeavailablechlorine.Totalchlorinedioxidetitrates
week in darkness, and then expose it to sunlight until no
as total residual chlorine.
chlorine remains. Filtration through a carbon filter is an
alternative process which requires less time to remove chlo-
6.8 Depending upon final pH, chlorination of waters con-
rine.
taining ammonia or nitrogenous organic compounds can pro-
duce high concentrations of dichloramine. This compound 8.3 pH 4.0 Buffer Solution—Dissolve 243 g of sodium
produces four to five times as much current as monochloram- acetate trihydrate and 480 g of glacial acetic acid in water and
ine. The current produced by as little as 5 mg/L of dichloram- dilute to 1 L.Apurchased pH 4.0 buffer of appropriate known
inecancausethemicroammeterpointertoreadoffscaleevenat purity is also acceptable.
the end point in the titration of free available chlorine. This
may be overcome by use of an opposing voltage in the Water and Sewage Works, May 1949, p. 171, and Journal American Water
Works Association, Vol 34, 1942, pp. 1227–1240.
apparatus’ circuitry. The instrument’s manufacturer should be
Reagent Chemicals, American Chemical Society Specifications, American
consulted in this regard.
Chemical Society, Washington, DC. For Suggestions on the testing of reagents not
listed by the American Chemical Society, see Annual Standards for Laboratory
6.9 Other oxidizing agents including: ozone, peroxide,
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
iodine, bromine, ferrate, and Caro’s acid will result in a
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
positive interference with this test. MD.
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D1253 − 14 (2021)
8.4 pH 7.0 Buffer Solution—Dissolve 25.4 g of monobasic each incremental addition. Plot the progress of the titration on
potassium phosphate and 86 g of dibasic sodium phosphate in linear graph paper with current on the vertical axis and titrant
water and dilute to 1 L. A purchased pH 7.0 buffer of volume on the horizontal axis. Add a small volume of titrant,
appropriate known purity is also acceptable. wait a few seconds, and plot the current-volume point on the
graph.
8.5 Biiodate, Solution Standard (0.0282 N)—Dissolve
0.9163 g of potassium biiodate in water and dilute to 1 L in a
NOTE3—Digitalinstrumentsareavailablewhichwillautomaticallyadd
at increments of titrant and plot the progress. When the titration is
volumetric flask. Store in an amber glass-stoppered bottle.
completed, these instruments also will calculate and display an inflection
8.6 Phenylarsine Oxide, Solution Standard (0.00564 N)—
based endpoint.
Dissolve 0.8 g of phenylarsine oxide in 150 mL of sodium
10.2.4 When using an instrument with analog display,
hydroxide solution (12 g/L). After settling, decant 110 mL of
readjust the potentiometer several times during the titration, if
this solution, add 800 mLof water, and bring to a pH of 9.0 by
necessary, to bring the pointer back on scale. It is typically not
adding hydrochloric acid (1 + 1). This should require about 2
necessary to readjust an instrument with digital display.
mL of HCl (1 + 1). Continue acidification with HCl (1 + 1)
10.2.5 Continue the analysis by determining at least three
untilapHof6to7isreached,asindicatedbyaglass-electrode
points spread over the downward sloping titration curve and at
system; then dilute to a total volume of 1L. Standardize to
least three points after the equivalence or end point. The latter
0.00564 N against 0.0282 N biiodate solution using the titrator
pointswillindicatepracticallynochangeincurrent.Pointsjust
(7.1) as the end-point indicator. Add 1 mL of chloroform for
before the end point shall be disregarded in its determination.
preservation.
The millilitres of titrant at the end point defined by the
8.7 Potassium Iodide Solution (50 g/L)—Dissolve 50 g of
intersection of the two linear sections of the titration curve
KI in water and dilute to 1 L. Add1gof sodium bicarbonate
should be recorded.
to stabilize the solution. Store in an amber bottle and avoid
10.3 Determination of Free Available Chlorine Residual:
direct exposure to sunlight.
10.3.1 Add 1 mL of pH 7.0 buffer solution (8.4)toa
200-mL sample.
9. Sampling
10.3.2 Repeat the phenylarsine oxide titration beginning
9.1 Collect the sample in accordance with Practices D3370.
with 10.2.2.
Take care that the sample is representative and keep it away
10.3.3 Note a rapid deflection of the pointer for each
from direct sunlight prior to analysis. Use of only glass sample
increment of titrant indicates the presence of free available
containers pretreated to eliminate chlorine demand is recom-
chlorine. Slight counterclockwise movements of the pointer
mended. See 7.2, Glassware.
after addition of individual drops of titrant is a drift effect and
9.2 All tests should be made as soon as possible after
does not indicate the presence of free available chlorine.
collection of the sample (not more than 5 min) because the
10.4 Determination of Combined Available Chlorine Re-
residual chlorine may diminish with time, due to the chlorine
sidual:
demand of the sample. Where time of contact is important, the
10.4.1 Complete the titration for the determination of free
elapsed time between the addition of chlorine and the deter-
available chlorine residual as in 10.3.
mination of chlorine should be taken into account.
10.4.2 To the same sample, add 1 mL of KI solution (8.7)
and1mLofpH4.0buffersolution(8.3)andrepeatthetitration
10. Procedure
as in 10.2.
10.1 For residual chlorine concentrations of 2.0 mg/L or
less, use a 200-mL sample. For greater concentrations, use a
100-mL sample. It is preferable that the size of the sample be
such that not more than 2 mL of titrant will be required to
complete the titration.
10.2 Determination of Total Residual Chlorine:
10.2.1 Add 1 mL of KI solution (8.7) to a 200-mL sample
and immediately add 1 mL of pH 4.0 buffer solution (8.3).
10.2.2 Immerse the electrodes in the sample and start th
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