ASTM D971-99a
(Test Method)Standard Test Method for Interfacial Tension of Oil Against Water by the Ring Method
Standard Test Method for Interfacial Tension of Oil Against Water by the Ring Method
SCOPE
1.1 This test method covers the measurement of, under nonequilibrium conditions, the interfacial tension of mineral oils against water.
1.2 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: D 971 – 99a
Standard Test Method for
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Interfacial Tension of Oil Against Water by the Ring Method
This standard is issued under the fixed designation D 971; 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 value for new mineral insulating oil indicates the absence of
most undesirable polar contaminants. The test is frequently
1.1 This test method covers the measurement of the inter-
applied to service-aged oils as an indication of the degree of
facial tension between mineral oil and water, under non-
deterioration.
equilibrium conditions.
1.2 This standard does not purport to address all of the
5. Apparatus (Figs. 1 and 2)
safety concerns, if any, associated with its use. It is the
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5.1 Tensiometer —Force measurement on the tensiometer
responsibility of the user of this standard to establish appro-
may be made using a torsion wire, load cell, or any other means
priate safety and health practices and determine the applica-
of linearly determining tension in the range of 0 to 100 mN/m.
bility of regulatory limitations prior to use.
5.1.1 Horizontal platform to hold the sample container
2. Referenced Documents should be capable of movement upward or downward using a
mechanical screw, lever mechanism, electronic drive, or any
2.1 ASTM Standards:
other means of precisely changing vertical position of the
D 117 Guide to Test Methods and Specifications for Elec-
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sample.
trical Insulating Oils of Petroleum Origin
5.2 Rings made of platinum or platinum-iridium alloy may
D 923 Test Method for Sampling Electrical Insulating Liq-
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be used. The ring should be welded into a continuous circle and
uids
attached to at least two parallel stirrups. Circumference of the
D 2285 Test Method for Interfacial Tension of Electrical
ring should be minimum 40 mm and diameter of the ring wire
Insulating Oils of Petroleum Origin Against Water by the
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should be about 0.3 mm. Ratio of the ring major radius (R) and
Drop-Weight Method
the wire radius (r) should be known (R/r) to at least three
3. Summary of Test Method significant figures. Stirrups should be at least 25 mm long.
5.2.1 The ring may be suspended from or rigidly fixed into
3.1 Interfacial Tension is determined by measuring the
the tensiometer force measuring system.
force necessary to detach a planar ring of platinum wire from
5.3 Sample Container—Glass beaker or clear cylindrical
the surface of the liquid of higher surface tension, that is,
container having a minimum diameter of 45 mm.
upward from the water-oil interface. To calculate the interfacial
tension, the force so measured is corrected by an empirically
6. Reagents
determined factor which depends upon the force applied, the
6.1 Purity of Reagents—Reagent grade chemicals shall be
densities of both oil and water, and the dimensions of the ring.
used in the test.
Measurements are made under rigidly standardized nonequi-
6.2 Purity of Water—Unless otherwise indicated, references
librium conditions in which the measurement is completed
to water shall be understood to mean distilled water or water of
within 60 s after formation of the interface.
equal purity.
4. Significance and Use
7. Preparation of Apparatus
4.1 Interfacial tension measurements on electrical insulating
7.1 Glass containers can be cleaned by rinsing in xylene,
oils provide a sensitive means of detecting small amounts of
hexane or another suitable hydrocarbon solvent, followed by a
soluble polar contaminants and products of oxidation. A high
rinse in acetone or methyl ethyl ketone. Following these rinses
they can be cleaned using detergent in hot water and rinsed
thoroughly with tap and then distilled water. Dry the glass
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This test method is under the jurisdiction of ASTM Committee D-27 on
vessel if not for immediate use.
Electrical Insulating Liquids and Gases and is the direct responsibility of Subcom-
mittee D27.07 on Physical Test.
Current edition approved Oct. 10, 1999. Published December 1999. Originally
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published as D 971 – 48 T. Last previous edition D 971 – 99. Tensiometers that use the Du Nouy principle for measuring interfacial and
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Annual Book of ASTM Standards, Vol 10.03. surface tension should be used.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
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D 971 – 99a
barely glow orange and should be heated for no more than 5 s.
Clean the ring immediately before each measurement.
7.3 The tensiometer should b
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