ASTM D1121-11

Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts

SIGNIFICANCE AND USE
Reserve alkalinity is the number of millilitres, to the nearest 0.1 mL of 0.100 N hydrochloric acid (HCl) required for the titration to a pH of 5.5 of a 10-mL sample of an undiluted, unused coolant, antirust, or coolant additive, and unused or used solutions thereof.
Reserve alkalinity is a term applied to engine coolants and antirusts to indicate the amount of alkaline components present in the product. It is frequently used for quality control during production, and values are often listed in specifications. When applied to used solutions, reserve alkalinity gives an approximate indication of the amount of remaining alkaline components. Unfortunately, the term is sometimes misused in that its numerical value is said to be directly related to coolant quality, the higher the number, the better the coolant. ASTM Committee D15 on Engine Coolants believes there is a need to correct some misconceptions and place the term in its proper perspective.
Reserve alkalinity (R.A.) as defined in Section 3 of this method is the number of millilitres of 0.1-N hydrochloric acid required to titrate 10 mL of concentrated coolant to a pH of 5.5. The term is not a completely accurate description of the property being measured because “alkalinity” usually refers to the pH range above 7.0.
A review of the origin of the term may be helpful in attempting to understand its proper use. When ethylene glycol was first used as an engine coolant, it was uninhibited. The need for inhibition soon became apparent and triethanolamine was incorporated. When solutions of this inhibited glycol were titrated with dilute hydrochloric acid, it was found that the steepest part of the neutralization curve occurred at a pH of about 5.0. Following the introduction of triethanolamine, other buffers, such as borates and phosphates, have been used. Titration to 5.5 was employed with these buffers which have an end point close to 5.5.
Generally, most metals in an automotive cooling system corrode less in ...
SCOPE
1.1 This test method covers the determination of the reserve alkalinity of new, unused engine coolants, and liquid antirusts as received, of used or unused aqueous dilutions of the concentrated materials, and of aqueous dilutions of solid antirusts.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety problems, 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: 30-Sep-2011
• ICS: 71.100.45 - Refrigerants and antifreezes
• Technical Committee: D15 - Engine Coolants and Related Fluids
• Drafting Committee: D15.04 - Chemical Properties

Relations

• Replaced By: ASTM D1121-11(2020) - Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts
• Effective Date: 01-Jan-2020

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: D1121 − 11
Standard Test Method for
1
Reserve Alkalinity of Engine Coolants and Antirusts
This standard is issued under the fixed designation D1121; 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 potentiometrically with 0.100 N hydrochloric acid to a pH of
5.5. The volume of acid used is reported to the nearest 0.1 mL.
1.1 This test method covers the determination of the reserve
The concentration of coolant or additive in the coolant solution
alkalinity of new, unused engine coolants, and liquid antirusts
shall be recorded if required, for calculation of depletion of the
as received, of used or unused aqueous dilutions of the
reserve alkalinity during performance tests.
concentrated materials, and of aqueous dilutions of solid
antirusts.
5. Significance and Use
1.2 The values stated in SI units are to be regarded as the
5.1 Reserve alkalinity is the number of millilitres, to the
standard.
nearest 0.1 mLof 0.100 N hydrochloric acid (HCl) required for
1.3 This standard does not purport to address all of the
the titration to a pH of 5.5 of a 10-mL sample of an undiluted,
safety problems, if any, associated with its use. It is the
unused coolant, antirust, or coolant additive, and unused or
responsibility of the user of this standard to establish appro-
used solutions thereof.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
5.2 Reserve alkalinity is a term applied to engine coolants
and antirusts to indicate the amount of alkaline components
2. Referenced Documents
present in the product. It is frequently used for quality control
2
during production, and values are often listed in specifications.
2.1 ASTM Standards:
When applied to used solutions, reserve alkalinity gives an
D1123 Test Methods for Water in Engine Coolant Concen-
approximate indication of the amount of remaining alkaline
trate by the Karl Fischer Reagent Method
components. Unfortunately, the term is sometimes misused in
D1176 Practice for Sampling and Preparing Aqueous Solu-
that its numerical value is said to be directly related to coolant
tions of Engine Coolants orAntirusts forTesting Purposes
quality, the higher the number, the better the coolant. ASTM
D1287 TestMethodforpHofEngineCoolantsandAntirusts
Committee D15 on Engine Coolants believes there is a need to
3. Terminology
correct some misconceptions and place the term in its proper
perspective.
3.1 Definitions:
3.1.1 reserve alkalinity, n—a term applied to engine coolant
5.3 Reserve alkalinity (R.A.) as defined in Section 3 of this
concentrates and antirusts to indicate the amount of alkaline
method is the number of millilitres of 0.1-N hydrochloric acid
inhibitors present in the product.
requiredtotitrate10mLofconcentratedcoolanttoapHof5.5.
The term is not a completely accurate description of the
4. Summary of Test Method
property being measured because “alkalinity” usually refers to
4.1 A 10-mL sample of concentrated coolant, antirust,
the pH range above 7.0.
coolantadditive,oranaqueousenginecoolantcontainingthese
5.4 A review of the origin of the term may be helpful in
products, is diluted to about 100 mL with water and titrated
attempting to understand its proper use. When ethylene glycol
was first used as an engine coolant, it was uninhibited. The
1
This test method is under the jurisdiction ofASTM Committee D15 on Engine
need for inhibition soon became apparent and triethanolamine
Coolants and Related Fluids and is the direct responsibility of Subcommittee
was incorporated. When solutions of this inhibited glycol were
D15.04 on Chemical Properties.
titrated with dilute hydrochloric acid, it was found that the
Current edition approved Oct. 1, 2011. Published October 2011. Originally
steepest part of the neutralization curve occurred at a pH of
approved in 1950. Last previous edition approved in 2007 as D1121 – 07. DOI:
10.1520/D1121-11.
about 5.0. Following the introduction of triethanolamine, other
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
buffers, such as borates and phosphates, have been used.
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Titrationto5.5wasemployedwiththesebufferswhichhavean
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. end point close to 5.5.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

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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.
Designation:D1121–07 Designation:D1121–11
Standard Test Method for
1
Reserve Alkalinity of Engine Coolants and Antirusts
This standard is issued under the fixed designation D1121; 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
1.1 This test method covers the determination of the reserve alkalinity of new, unused engine coolants, and liquid antirusts as
received, of used or unused aqueous dilutions of the concentrated materials, and of aqueous dilutions of solid antirusts.
1.2 The values stated in SI units are to be regarded as the standard.
1.3 This standard does not purport to address all of the safety problems, 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:
D1123 Test Methods for Water in Engine Coolant Concentrate by the Karl Fischer Reagent Method
D1176 Practice for Sampling and Preparing Aqueous Solutions of Engine Coolants or Antirusts for Testing Purposes
D1287 Test Method for pH of Engine Coolants and Antirusts
3. Terminology
3.1 Definition:
3.1.1 reserve alkalinity, n—a term applied to engine coolant concentrates and antirusts to indicate the amount of alkaline
inhibitors present in the product.
4. Summary of Test Method
4.1 A10-mLsample of concentrated coolant, antirust, coolant additive, or an aqueous engine coolant containing these products,
is diluted to about 100 mL with water and titrated potentiometrically with 0.100 N hydrochloric acid to a pH of 5.5. The volume
of acid used is reported to the nearest 0.1 mL. The concentration of coolant or additive in the coolant solution shall be recorded
if required, for calculation of depletion of the reserve alkalinity during performance tests.
5. Significance and Use
5.1 Reserve alkalinity is the number of millilitres, to the nearest 0.1 mL of 0.100 N hydrochloric acid (HCl) required for the
titration to a pH of 5.5 of a 10-mL sample of an undiluted, unused coolant, antirust, or coolant additive, and unused or used
solutions thereof.
5.2 Reserve alkalinity is a term applied to engine coolants and antirusts to indicate the amount of alkaline components present
intheproduct.Itisfrequentlyusedforqualitycontrolduringproduction,andvaluesareoftenlistedinspecifications.Whenapplied
to used solutions, reserve alkalinity gives an approximate indication of the amount of remaining alkaline components.
Unfortunately, the term is sometimes misused in that its numerical value is said to be directly related to coolant quality, the higher
the number, the better the coolant. ASTM Committee D-15D15 on Engine Coolants believes there is a need to correct some
misconceptions and place the term in its proper perspective.
5.3 Reserve alkalinity (R.A.) as defined in Section 3 of this method is the number of millilitres of 0.1-N hydrochloric acid
required to titrate 10 mL of concentrated coolant to a pH of 5.5. The term is not a completely accurate description of the property
being measured because “alkalinity” usually refers to the pH range above 7.0.
1
This test method is under the jurisdiction ofASTM Committee D15 on Engine Coolants and Related Fluids and is the direct responsibility of Subcommittee D15.04 on
Chemical Properties.
Current edition approved AprilOct. 1, 2007.2011. Published April 2007.October 2011. Originally approved in 1950. Last previous edition approved in 20032007 as
D1121–98(2003).D1121 – 07. DOI: 10.1520/D1121-07.10.1520/D1121-11.
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.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
1

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D1121–11
5.4 Areview of the origin of the term may be helpful in attempting to understand its proper use.When ethylene glycol was first
used as an engine coolant, it was uninhibited.The need for inhibition soon became apparent and triethano
...