ASTM D1126-12

Standard Test Method for Hardness in Water

SIGNIFICANCE AND USE
5.1 Hardness salts in water, notably calcium and magnesium, are the primary cause of tube and pipe scaling, which frequently causes failures and loss of process efficiency due to clogging or loss of heat transfer, or both.  
5.2 Hardness is caused by any polyvalent cations, but those other than Ca and Mg are seldom present in more than trace amounts. The term hardness was originally applied to water in which it was hard to wash; it referred to the soap-wasting properties of water. With most normal alkaline water, these soap-wasting properties are directly related to the calcium and magnesium content.
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.4 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: 29-Feb-2012
• 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 D1126-02(2007)e1 - Standard Test Method for Hardness in Water
• Effective Date: 01-Mar-2012
• Referred By: ASTM D6469-20 - Standard Guide for Microbial Contamination in Fuels and Fuel Systems
• Effective Date: 01-Mar-2012
• 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: 01-Mar-2012
• Referred By: ASTM D1782-17 - Standard Test Methods for Operating Performance of Particulate Cation-Exchange Materials
• Effective Date: 01-Mar-2012
• Referred By: ASTM D7715-12(2021) - Standard Specification for Fully-Formulated Glycerin Base Engine Coolant for Heavy-Duty Engines
• Effective Date: 01-Mar-2012
• Referred By: ASTM D3306-21 - Standard Specification for Glycol Base Engine Coolant for Automobile and Light-Duty Service
• Effective Date: 01-Mar-2012
• Referred By: ASTM D7714-11(2021) - Standard Specification for Glycerin Base Engine Coolant for Automobile and Light-Duty Service
• Effective Date: 01-Mar-2012
• Referred By: ASTM E1945-21 - Standard Test Method for Percent Dispersibility
• Effective Date: 01-Mar-2012
• Referred By: ASTM D6210-17 - Standard Specification for Fully-Formulated Glycol Base Engine Coolant for Heavy-Duty Engines<rangeref></rangeref >
• Effective Date: 01-Mar-2012
• Referred By: ASTM E1116-98(2019) - Standard Test Method for Emulsification Characteristics of Pesticide Emulsifiable Concentrates
• Effective Date: 01-Mar-2012
• Referred By: ASTM D3376-18 - Standard Test Methods of Sampling and Testing Pulps to be Used in the Manufacture of Electrical Insulation
• Effective Date: 01-Mar-2012
• Referred By: ASTM D3342-22 - Standard Test Method for Dispersion Stability of New (Unused) Rolling Oil Dispersions in Water
• Effective Date: 01-Mar-2012
• Referred By: ASTM D5752-10(2017) - Standard Specification for Supplemental Coolant Additives (SCAs) for Use in Precharging Coolants for Heavy-Duty Engines
• Effective Date: 01-Mar-2012
• Referred By: ASTM E1673-21 - Standard Test Method for Percent Suspensibility
• Effective Date: 01-Mar-2012
• Referred By: ASTM D7518-20 - Standard Specification for 1,3 Propanediol (PDO) Base Engine Coolant for Automobile and Light-Duty Service
• Effective Date: 01-Mar-2012

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: D1126 − 12
Standard Test Method for
1
Hardness in Water
This standard is issued under the fixed designation D1126; 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.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope* 3. Terminology
1.1 Thistestmethodcoversthedeterminationofhardnessin 3.1 Definitions—For definitions of terms used in this test
water by titration. This test method is applicable to waters that method, refer to Terminology D1129.
are clear in appearance and free of chemicals that will complex 3.2 Definitions of Terms Specific to This Standard:
calcium or magnesium. The lower detection limit of this test
3.2.1 equivalent per million (epm), n—a unit chemical
methodisapproximately2to5mg/LasCaCO ;theupperlimit
equivalent weight of solute per million unit weights of solu-
3
can be extended to all concentrations by sample dilution. It is tion.
possible to differentiate between hardness due to calcium ions
3.2.2 laboratory control sample (LCS), n—a solution with
and that due to magnesium ions by this test method.
certified hardness.
1.2 This test method was tested on reagent water only. It is
the user’s responsibility to ensure the validity of the test 4. Summary of Test Method
method for waters of untested matrices.
4.1 Calcium and magnesium ions in water are sequestered
1.3 The values stated in SI units are to be regarded as
by the addition of disodium ethylenediamine tetraacetate. The
standard. No other units of measurement are included in this
endpointofthereactionisdetectedbymeansofChromeBlack
3
standard.
T , which has a red color in the presence of calcium and
magnesium and a blue color when they are sequestered.
1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
5. Significance and Use
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
5.1 Hardness salts in water, notably calcium and
bility of regulatory limitations prior to use.
magnesium, are the primary cause of tube and pipe scaling,
which frequently causes failures and loss of process efficiency
2. Referenced Documents
due to clogging or loss of heat transfer, or both.
2
2.1 ASTM Standards:
5.2 Hardness is caused by any polyvalent cations, but those
D1066 Practice for Sampling Steam
other than Ca and Mg are seldom present in more than trace
D1129 Terminology Relating to Water
amounts. The term hardness was originally applied to water in
D1193 Specification for Reagent Water
which it was hard to wash; it referred to the soap-wasting
D2777 Practice for Determination of Precision and Bias of
properties of water. With most normal alkaline water, these
Applicable Test Methods of Committee D19 on Water
soap-wasting properties are directly related to the calcium and
D3370 Practices for Sampling Water from Closed Conduits
magnesium content.
D5847 Practice for Writing Quality Control Specifications
for Standard Test Methods for Water Analysis
6. Interferences
6.1 The substances shown in Table 1 represent the highest
concentrations that have been found not to interfere with this
1
This test method is under the jurisdiction of ASTM Committee D19 on Water
determination.
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
in Water.
6.2 The test method is not suitable for highly colored
Current edition approved March 1, 2012. Published March 2012. Originally
ε1 waters, which obscure the color change of the indicator.
approved in 1950. Last previous edition approved in 2007 as D1126 – 02 (2007) .
DOI: 10.1520/D1126-12.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
3
Standards volume information, refer to the standard’s Document Summary page on 3–Hydroxy–4-(1–hydroxy-2–napththyl) azo-7–nitro–1 naphthalenesulfonic
the ASTM website. acid, sodium salt, Color Index 14645.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D1126 − 12
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
Substance Interference Interference
steps as follows:
in the To
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: D1126 − 02 (Reapproved 2007) D1126 − 12
Standard Test Method for
1
Hardness in Water
This standard is issued under the fixed designation D1126; 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.
This standard has been approved for use by agencies of the Department of Defense.
1
ε NOTE—Added acronym to 3.1.2 and updated 11.5 editorially in August 2007.
1. Scope 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 CaCO ; the upper limit can be extended to all concentrations by sample dilution. It is possible
3
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 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Closed Conduits
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
3. Terminology
3.1 Definitions—For definitions of terms used in this test method, refer to Terminology D1129.
3.2 Definitions:Definitions of Terms Specific to This Standard:
3.2.1 equivalent per million (epm), n—a unit chemical equivalent weight of solute per million unit weights of solution.
3.2.2 laboratory control sample (LCS), n—a solution with certified hardness.
3.1.3 For definitions of other terms used in this test method, refer to Terminology D1129.
4. Summary of Test Method
4.1 Calcium and magnesium ions in water are sequestered by the addition of disodium ethylenediamine tetraacetate. The end
3
point of the reaction is detected by means of Chrome Black T , which has a red color in the presence of calcium and magnesium
and a blue color when they are sequestered.
1
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.
Current edition approved Aug. 1, 2007March 1, 2012. Published August 2007March 2012. Originally approved in 1950. Last previous edition approved in 20022007 as
ε1
D1126 – 02.D1126 – 02 (2007) . DOI: 10.1520/D1126-02R07E01.10.1520/D1126-12.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
3–Hydroxy–4-(1–hydroxy-2–napththyl) azo-7–nitro–1 naphthalenesulfonic acid, sodium salt, Color Index 14645.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D1126 − 12
TABLE 1 Freedom of Reaction from Interferences
Maximum Maximum
Concentration Concentration
Without Without
Substance Interference Interference
in the Total in the Calcium
Hardness Hardness
Test, mg/L Test, mg/L
+ + +
Aluminum, Al 20 5
+ A
Ammonium, NH 2 000
4
−
Bicarbonate, HCO . 500
3
Bromine, Br . 2
+ +
Cadmium, Cd 20 .
− −
Carbonate, CO 1 000 50
3
−
Chloride, Cl 10 000 .
Chlorine, Cl . 2
− −
Chromate, CrO 500 500
4
+ +
Cobalt, Co 0.3 .
+ +
Copper, Cu 20 2
+ ++ B
Iron, ferric, Fe 10 20
+ + B
Iron, ferrous, Fe 10 20
++
Lead, Pb 20 5
+ + C C
Manganese, Mn 1 10
+ + D
Nickel, Ni 0.5 .
−
Nitrate, NO 500 500
3
−
Nitrite, N
...

This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation:D1126–02(Reapproved2007) Designation:D1126–12
Standard Test Method for
1
Hardness in Water
This standard is issued under the fixed designation D1126; 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.
This standard has been approved for use by agencies of the Department of Defense.
1
´ NOTE—Added acronym to 3.1.2 3.2.2 and updated 11.5 editorially in August 2007.
1. 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 CaCO ; the upper limit can be extended to all concentrations by sample dilution. It is possible
3
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
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D1066 Practice for Sampling Steam
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3370 Practices for Sampling Water from Closed Conduits
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
3. Terminology
3.1 Definitions:
3.1.1For definitions of terms used in this test method, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 equivalent per million (epm), n—a unit chemical-equivalent weight of solute per million unit weights of solution.
3.1.23.2.2 laboratory control sample (LCS), n—a solution with certified hardness.
3.1.3For definitions of other terms used in this test method, refer to Terminology D1129.
4. Summary of Test Method
4.1 Calcium and magnesium ions in water are sequestered by the addition of disodium ethylenediamine tetraacetate. The end
3
point of the reaction is detected by means of Chrome Black T , which has a red color in the presence of calcium and magnesium
and a blue color when they are sequestered.
1
This test method is under the jurisdiction ofASTM Committee D19 onWater and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents inWater.
Current edition approved Aug. 1, 2007. Published August 2007. Originally approved in 1950. Last previous edition approved in 2002 as D1126–02. DOI:
10.1520/D1126-02R07E01.
e01
Current edition approved March 1, 2012. Published March 2012. Originally approved in 1950. Last previous edition approved in 2007 as D1126 – 02(2007) . DOI:
10.1520/D1126-12.
2
For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
3
3–Hydroxy–4-(1–hydroxy-2–napththyl) azo-7–nitro–1 naphthalenesulfonic acid, sodium salt, Color Index 14645.
*A Summary of Changes section appears at the end of this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

---------------------- Page: 1 ----------------------
D1126–12
5. Significance and Use
5.1 Hardness salts in water, notably calcium and magnesium, are the primary cause of tube and pipe scaling, which frequently
causes failures and loss of process efficiency due to clogging or loss of heat transfer, or both.
5.2 Hardness is caused by any polyvalent cations, but those other than Ca and Mg are seldom present in more than trace
amounts.The term hardness was originally applied to water in which it was hard to wash; it referred to the soap-wasting properties
of water. With most normal alkali
...