ASTM D1126-02

Standard Test Method for Hardness in Water

SCOPE
1.1 This test method covers the determination of hardness in water by titration. This test method is applicable to waters that are clear in appearance and free of chemicals that will complex calcium or magnesium. The lower detection limit of this test method is approximately 2 to 5 mg/L as CaCO3; the upper limit can be extended to all concentrations by sample dilution. It is possible to differentiate between hardness due to calcium ions and that due to magnesium ions by this test method.
1.2 This test method was tested on reagent water only. It is the user's responsibility to ensure the validity of the test method for waters of untested matrices.
1.3 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.

General Information

• Status: Historical
• Publication Date: 09-May-2002
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.05 - Inorganic Constituents in Water

Relations

• Replaces: ASTM D1126-96 - Standard Test Method for Hardness in Water
• Effective Date: 10-May-2002
• Replaced By: ASTM D1126-02(2007)e1 - Standard Test Method for Hardness in Water
• Effective Date: 01-Aug-2007
• Referred By: ASTM D1782-17 - Standard Test Methods for Operating Performance of Particulate Cation-Exchange Materials
• Effective Date: 10-May-2002
• Referred By: ASTM C375-22 - Standard Classification of Water Used in Milling of Porcelain Enamel
• Effective Date: 10-May-2002
• Referred By: ASTM D7715-12(2021) - Standard Specification for Fully-Formulated Glycerin Base Engine Coolant for Heavy-Duty Engines
• Effective Date: 10-May-2002
• Referred By: ASTM D6210-17 - Standard Specification for Fully-Formulated Glycol Base Engine Coolant for Heavy-Duty Engines<rangeref></rangeref >
• Effective Date: 10-May-2002
• Referred By: ASTM D3306-21 - Standard Specification for Glycol Base Engine Coolant for Automobile and Light-Duty Service
• Effective Date: 10-May-2002
• Referred By: ASTM E1391-03(2023) - Standard Guide for Collection, Storage, Characterization, and Manipulation of Sediments for Toxicological Testing and for Selection of Samplers Used to Collect Benthic Invertebrates
• Effective Date: 10-May-2002
• Referred By: ASTM D3342-22 - Standard Test Method for Dispersion Stability of New (Unused) Rolling Oil Dispersions in Water
• Effective Date: 10-May-2002
• Referred By: ASTM D7518-20 - Standard Specification for 1,3 Propanediol (PDO) Base Engine Coolant for Automobile and Light-Duty Service
• Effective Date: 10-May-2002
• Referred By: ASTM D7517-19 - Standard Specification for Fully-Formulated 1,3 Propanediol (PDO) Base Engine Coolant for Heavy-Duty Engines
• Effective Date: 10-May-2002
• Referred By: ASTM D5752-10(2017) - Standard Specification for Supplemental Coolant Additives (SCAs) for Use in Precharging Coolants for Heavy-Duty Engines
• Effective Date: 10-May-2002
• Referred By: ASTM D4985-10(2023) - Standard Specification for Low Silicate Ethylene Glycol Base Engine Coolant for Heavy Duty Engines Requiring a Pre-Charge of Supplemental Coolant Additive (SCA)
• Effective Date: 10-May-2002
• Referred By: ASTM D3376-18 - Standard Test Methods of Sampling and Testing Pulps to be Used in the Manufacture of Electrical Insulation
• Effective Date: 10-May-2002
• Referred By: ASTM D7714-11(2021) - Standard Specification for Glycerin Base Engine Coolant for Automobile and Light-Duty Service
• Effective Date: 10-May-2002

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 1126–02
Standard Test Method for
1
Hardness in Water
This standard is issued under the fixed designation D 1126; 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.
1. Scope 3.1.1 equivalent per million (epm), n—a unit chemical
equivalent weight of solute per million unit weights of solu-
1.1 Thistestmethodcoversthedeterminationofhardnessin
tion.
water by titration. This test method is applicable to waters that
3.1.2 laboratorycontrolsample,n—asolutionwithcertified
are clear in appearance and free of chemicals that will complex
hardness.
calcium or magnesium. The lower detection limit of this test
3.1.3 For definitions of other terms used in this test method,
methodisapproximately2to5mg/LasCaCO ;theupperlimit
3
refer to Terminology D 1129.
can be extended to all concentrations by sample dilution. It is
possible to differentiate between hardness due to calcium ions
4. Summary of Test Method
and that due to magnesium ions by this test method.
4.1 Calcium and magnesium ions in water are sequestered
1.2 This test method was tested on reagent water only. It is
by the addition of disodium ethylenediamine tetraacetate. The
the user’s responsibility to ensure the validity of the test
endpointofthereactionisdetectedbymeansofChromeBlack
method for waters of untested matrices.
4
T , which has a red color in the presence of calcium and
1.3 This standard does not purport to address all of the
magnesium and a blue color when they are sequestered.
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 Hardness salts in water, notably calcium and magne-
bility of regulatory limitations prior to use.
sium, are the primary cause of tube and pipe scaling, which
2. Referenced Documents frequently causes failures and loss of process efficiency due to
clogging or loss of heat transfer, or both.
2.1 ASTM Standards:
2 5.2 Hardness is caused by any polyvalent cations, but those
D 1066 Practice for Sampling Steam
2 other than Ca and Mg are seldom present in more than trace
D 1129 Terminology Relating to Water
2 amounts. The term hardness was originally applied to water in
D 1193 Specification for Reagent Water
which it was hard to wash; it referred to the soap-wasting
D 3370 Practices for Sampling Water from Closed Con-
2 properties of water. With most normal alkaline water, these
duits
soap-wasting properties are directly related to the calcium and
D 5847 Practice for Writing Quality Control Specifications
3 magnesium content.
for Standard Test Methods for Water Analysis
6. Interferences
3. Terminology
6.1 The substances shown in Table 1 represent the highest
3.1 Definitions:
concentrations that have been found not to interfere with this
determination.
1
This test method is under the jurisdiction of ASTM Committee D19 on Water
6.2 The test method is not suitable for highly colored
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
waters, which obscure the color change of the indicator.
in Water.
Current edition approved May 10, 2002. Published June 2002. Originally
published as D1126 – 50 T. Last previous edition D1126 – 96.
2 4
Annual Book of ASTM Standards, Vol 11.01. 3–Hydroxy–4-(1–hydroxy-2–napththyl) azo-7–nitro–1 naphthalenesulfonic
3
Annual Book of ASTM Standards, Vol 11.02. acid, sodium salt, Color Index 14645.
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1

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D1126–02
TABLE 1 Freedom of Reaction from Interferences
7.3 Ammonium Hydroxide Solution (1 + 4)—Mix 1 volume
Maximum Maximum of NH OH (sp gr 0.90) with 4 volumes of water.
4
Concentration Concentration
7.4 Buffer Solution—Prepare the buffer solution in three
Without Without
steps as follows:
Substance Interference Interference
in the Total in the Calcium 7.4.1 Dissolve 40 g of sodium tetraborate
Hardness Hardness
(Na B O ·10H O) in 800 mL of water.
2 4 7 2
Test, mg/L Test, mg/L
7.4.2 Dissolve 10 g of sodium hydroxide (NaOH), 10 g of
sodium sulfide (Na S·9H O), and 10 g of potassium sodium
+++
2 2
Aluminum, Al 20 5
+ A
tartrate (KNaC O ·4H O) in 100 mL of water.
Ammonium, NH 2 000
4 4 6 2
−
Bicarbonate, HCO . 500
3
7.4.3 When cool mix the two solutions and add1gof
Bromine, Br . 2
magnesium disodium ethylenediamine tetraacetate, having a
++
Cadmium, Cd 20 .
−−
...