ASTM D 1401 and ASTM D 2711
In the petroleum industry, the term emulsion
usually applies to an emulsion of oil and water.
Though mutually soluble only to a slight degree,
these substances can, under certain circum-
stances, be intimately dispersed in one another
to form a homogeneous mixture. Such a mixture
is an oil-water emulsion, and it is usually milky
or cloudy in appearance.
Commercial oils vary in emulsibility. A highly
refined straight mineral oil resists emulsification.
Even after it has been vigorously agitated with
water, an oil of this type tends to separate rap-
idly from the water when the mixture Is at rest.
Emulsification can be promoted, however, by
agitation and by the presence of certain con-
taminants or ingredients added to the oil. The
more readily the emulsion can be formed and
the greater its stability, the greater the
emulsibility of the oil. Some products, such as
soluble cutting fluids, require good emulsibility
and are formulated with special emulsifying
With many other products, however, such as
turbine oils and crankcase oils, the opposite
characteristic is desired. To facilitate the re-
moval of entrained water, these products must
resist emulsification. The more readily they
break from an emulsion, the better their
Two tests for measuring demulsibility character-
istics have been standardized by the ASTM. The
older of the two is ASTM method D 1401, which
was developed specifically for steam turbine oils
having viscosities of 150-450 Saybolt seconds
at 100° F. It can be used for oils of other
viscosities if minor changes in the test
procedure are made. This method is the one
recommended for use with synthetic oils.
The second method, ASTM D 2711 is designed
for use with R&O (rust and oxidation inhibited)
oils. It can also be used for other types of oils,
although minor modifications are required when
testing EP (extreme pressure) oils.
ASTM D 1401: A 40-ml sample of oil and 40 mi
of distilled water are put into a 100-ml graduate.
The mixture is stirred for 5 minutes while main-
tained at a temperature of 130° F. The time
required for separation of the emulsion into its
oil and water components is recorded. If, at the
end of an hour, 3 or more milliliters of emulsion
still remain, the test is discontinued and the
milliliters of oil, water, and emulsion are re-
ported. The 3 measurements are presented in
that order and are separated by hyphens. Test
time, in minutes, is shown in parenthesis.
ASTM D 2711: A 405-ml sample of oil and 45
ml of distilled water, are stirred together for 5
minutes in a special graduated separator funnel,
while maintained at 180° F, After a 5-hour set-
tling period, a 50-ml sample drawn from near
the top of the oil layer is centrifuged to
determine the "percent water in the oil." The
"milliliters of free water" is also measured and
reported. Then the mixture is siphoned off until
only 100 ml remain in the bottom of the funnel.
This is centrifuged and the milliliters of water
and of emulsion are reported. The amount of
water from this step is added to the amount of
free water and the "total water" is reported.
When used to test EP gear oils, amount of oil is
reduced to 360 ml while the amount of water is
increased to 90 mi.
Navy Emulsion test: This procedure is similar
to ASTM D 1401. Measurements are made after
a 1-hour settling period (for oil tested at 130° F)
or after a 1/2-hour settling period (for oils tested
at 180° F), and the sample may be considered
to pass if the emulsion does not exceed 3 milli-
A-1 (FIST 2-4 11/90)