ASTM D3321-19(2023)

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.
Designation: D3321 − 19 (Reapproved 2023)
Standard Test Method for
Use of the Refractometer for Field Test Determination of the
Freezing Point of Aqueous Engine Coolants
This standard is issued under the fixed designation D3321; 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.
1. Scope E691 Practice for Conducting an Interlaboratory Study to
Determine the Precision of a Test Method
1.1 This test method covers the use of a portable refracto-
meter for determining the approximate freezing protection
3. Summary of Test Method
provided by ethylene and propylene glycol-based coolant
solutions as used in engine cooling systems and special
3.1 These coolant testers are critical-angle refractometers
applications.
designed for rapid, approximate measurement of ethylene and
propylene glycol coolant freezing point protection. Only a few
NOTE 1—Some instruments have a supplementary freezing protection
drops of test solution are required. Some testers automatically
scale for methoxypropanol coolants. Others carry a supplemental scale
calibrated in density or specific gravity readings of sulfuric acid solutions
correct for ambient air temperature and the temperature of the
so that the refractometer can be used to determine the charged condition
solution being tested. The instrument is rugged, simple to read,
of lead acid storage batteries.
and easy to clean and maintain.
1.2 The values stated in SI units are to be regarded as
3.2 The coolant freezing point readings are taken at points
standard. The values given in parentheses after SI units are
where the dividing line between light and dark crosses the
provided for information only and are not considered standard.
scales. Some refractometers have a coolant scale for indicating
1.3 This standard does not purport to address all of the
the freezing point of aqueous ethylene glycol coolants only,
safety concerns, if any, associated with its use. It is the
while other refractometers also have a scale for indicating the
responsibility of the user of this standard to establish appro-
freezing point of aqueous propylene glycol coolants. The range
priate safety, health, and environmental practices and deter-
of the scales varies from one device to another.
mine the applicability of regulatory limitations prior to use.
3.3 Freezing point measurements are concentration-related
1.4 This international standard was developed in accor-
values and are in turn directly related to refractive index. It has
dance with internationally recognized principles on standard-
been empirically determined that freezing point measurements
ization established in the Decision on Principles for the
are accurate within 1 °C (2 °F).
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Significance and Use
Barriers to Trade (TBT) Committee.
4.1 This practice is commonly used by vehicle service
2. Referenced Documents
personnel to determine the freezing point, in degrees Celsius or
2.1 ASTM Standards:
Fahrenheit, of aqueous solutions of commercial ethylene and
D1177 Test Method for Freezing Point of Aqueous Engine
propylene glycol-based coolant. A durable hand-held refracto-
Coolants
meter is available that reads the freezing point, directly, in
E177 Practice for Use of the Terms Precision and Bias in
degrees Celsius or Fahrenheit, when a few drops of engine
ASTM Test Methods
coolant are properly placed on the temperature-compensated
prism surface of the refractometer. This refractometer is for
glycol and water solutions, and is not suitable for other coolant
This test method is under the jurisdiction of ASTM Committee D15 on Engine
solutions.
Coolants and Related Fluids and is the direct responsibility of Subcommittee
D15.03 on Physical Properties. 4.2 The hand-held refractometer should be calibrated before
Current edition approved Sept. 1, 2023. Published September 2023. Originally
use (see Section 7).
approved in 1974. Last previous edition approved in 2019 as D3321 – 19. DOI:
10.1520/D3321-19R23.
4.3 Care must be taken to use the correct glycol freezing
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
point scale for the glycol type being measured. Use of the
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
wrong glycol scale can result in freezing point errors of 18 and
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. more degrees Fahrenheit.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D3321 − 19 (2023)
4.4 Ethylene glycol/propylene glycol mixtures will result in
inaccurate freezing point measurements using either freezing
point scale.
5. Interferences
5.1 Interference can occur if the mixture is contaminated or
if the prism surface is not clean. The presence of other glycols
such as diethylene glycol in small amounts will not cause
interference.
6. Apparatus
6.1 The hand-held critical angle refractometer is a rugged
die-cast portable instrument that is covered with a high-impact
plastic to minimize damage to the eyepiece lens if dropped. A
polished glass prism is opposite the viewing end. A hinged
plastic cover is moved over the prism (sampling end) to allow
for even sample distribution and prevent liquid sample spillage
during the test. No eyepiece or prism adjustments are required
for sample testing.
6.2 The telescopic recessed eyepiece is located at one end
and the graduated, translucent prism on the opposite end (see
Fig. 1).
7. Calibration
7.1 Calibration of these coolant testers should periodically
be verified by testing a water sample in accordance with the
procedure outlined in Section 8.
7.2 If the sample tested deviates from 0 °C (+32 °F) the
coolant tester is out of calibration and should be recalibrated.
7.3 This calibration test is best performed with the coolant
tester and water sample at room temperature. If the instrument
used is designed to be automatically temperature compensated,
work within the stated temperature-compensated range.
8. Procedure
8.1 Cleaning—Before using, swing back the plastic cover at
FIG. 2 Cleaning
the slanted end of the tester exposing both the measuring
window and the bottom of the plastic cover. Wipe both clean
and dry with tissue or clean soft cloth. Close the plastic cover
8.3.1 Point the instrument toward any light source (for
(see Fig. 2).
example, a headlight) and look into the eyepiece (Fig. 4).
8.3.2 The freeze point protection is the point where the
8.2 Testing Coolant Solution—Commercial instruments are
dividing line between light and dark (edge of t
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