ASTM D1121-07
(Test Method)Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts
Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts
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.
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Designation:D1121–07
Standard Test Method for
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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 products, is diluted to about 100 mL with water and titrated
potentiometrically with 0.100 N hydrochloric acid to a pH of
1.1 This test method covers the determination of the reserve
5.5. The volume of acid used is reported to the nearest 0.1 mL.
alkalinity of new, unused engine coolants, and liquid antirusts
The concentration of coolant or additive in the coolant solution
as received, of used or unused aqueous dilutions of the
shall be recorded if required, for calculation of depletion of the
concentrated materials, and of aqueous dilutions of solid
reserve alkalinity during performance tests.
antirusts.
1.2 The values stated in SI units are to be regarded as the
5. Significance and Use
standard.
5.1 Reserve alkalinity is the number of millilitres, to the
1.3 This standard does not purport to address all of the
nearest 0.1 mLof 0.100 N hydrochloric acid (HCl) required for
safety problems, if any, associated with its use. It is the
the titration to a pH of 5.5 of a 10-mL sample of an undiluted,
responsibility of the user of this standard to establish appro-
unused coolant, antirust, or coolant additive, and unused or
priate safety and health practices and determine the applica-
used solutions thereof.
bility of regulatory limitations prior to use.
5.2 Reserve alkalinity is a term applied to engine coolants
2. Referenced Documents and antirusts to indicate the amount of alkaline components
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present in the product. It is frequently used for quality control
2.1 ASTM Standards:
during production, and values are often listed in specifications.
D1123 Test Methods for Water in Engine Coolant Concen-
When applied to used solutions, reserve alkalinity gives an
trate by the Karl Fischer Reagent Method
approximate indication of the amount of remaining alkaline
D1176 Practice for Sampling and Preparing Aqueous Solu-
components. Unfortunately, the term is sometimes misused in
tions of Engine Coolants orAntirusts for Testing Purposes
that its numerical value is said to be directly related to coolant
D1287 Test Method for pH of Engine Coolants and Anti-
quality, the higher the number, the better the coolant. ASTM
rusts
CommitteeD-15onEngineCoolantsbelievesthereisaneedto
3. Terminology correct some misconceptions and place the term in its proper
perspective.
3.1 Definition:
5.3 Reserve alkalinity (R.A.) as defined in Section 3 of this
3.1.1 reserve alkalinity, n—a term applied to engine coolant
method is the number of millilitres of 0.1-N hydrochloric acid
concentrates and antirusts to indicate the amount of alkaline
requiredtotitrate10mLofconcentratedcoolanttoapHof5.5.
inhibitors present in the product.
The term is not a completely accurate description of the
4. Summary of Test Method
property being measured because “alkalinity” usually refers to
the pH range above 7.0.
4.1 A 10-mL sample of concentrated coolant, antirust,
5.4 A review of the origin of the term may be helpful in
coolantadditive,oranaqueousenginecoolantcontainingthese
attempting to understand its proper use. When ethylene glycol
was first used as an engine coolant, it was uninhibited. The
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This test method is under the jurisdiction ofASTM Committee D15 on Engine
need for inhibition soon became apparent and triethanolamine
Coolants and is the direct responsibility of Subcommittee D15.04 on Chemical
was incorporated. When solutions of this inhibited glycol were
Properties.
Current edition approved April 1, 2007. Published April 2007. Originally titrated with dilute hydrochloric acid, it was found that the
approved in 1950. Last previous edition approved in 2003 as D1121 – 98(2003).
steepest part of the neutralization curve occurred at a pH of
DOI: 10.1520/D1121-07.
about 5.0. Following the introduction of triethanolamine, other
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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 service@astm.org. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website.
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D1121–07
Titrationto5.5wasemployedwiththesebufferswhichhavean
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