FED-STD-791D
Method 3470.1
September 30, 1986
HOMOGENEITY AND MISCIBILITY OF OILS
1. SCOPE
1.1 This test determines if an oil is and will remain homogeneous, and if it is
miscible with certain standard reference oils after being submitted to a prescribed cycle
of temperature changes.
2. SUMMARY
2.1 Using standard reference oils, an oil sample is tested to determine if it is and
will remain homogeneous and if it is miscible with the reference oils. A sample oil is
mixed thoroughly with a reference oil and heated. When the oils reach room
temperature, they are observed for color and evidence of separation. The pour point is
determined for each oil. A series of tests are made in cooling baths at 12C above the
expected pour point. The temperature is read at a multiple of 3C. The test jar is
removed and it is tilted to determine if there is movement of the oil. The test jar is
placed in successively lower cooling baths until the oil has ceased to flow. When the oil
does not flow when the jar is tilted, hold the jar in a horizontal position for 5 s and
observe the oil. If the oil shows any movement under these conditions, place the jar in
the cooling bath at the next lower temperature. The test is continued under these
conditions until there is no movement when the jar is tilted in a horizontal position. The
thermometer reading is recorded at this temperature. The samples are thawed. When the
cloudiness has barely disappeared, the color and evidence of separation is recorded.
After the samples reach room temperature, the thermometers are removed and the
samples are heated to 232C in an oil bath. The sample jars are corked and stored at their
pour points for 18 to 24 h. When the cloudiness has barely disappeared, after heating,
the color and evidence of separation is recorded. The last procedure is repeated. The
data is recorded on the Homogeneity and Miscibility Test forms.
3. SAMPLE SIZE
3.1 Approximately 300 mL of oil to be tested.
4. REFERENCE, STANDARDS, AND APPARATUS
4.1 Test jar. A test jar of clear glass, cylindrical form, flat bottom, approximately
3.0 to 3.5 cm I.D. and 12 to 13 cm in height.
4.2 Thermometers. -80 to +21C range, conforming to ASTM E 1.
4.3 Cork. To fit the test jar, bored centrally to take the test thermometer.
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