Official Method Tr 1a-64
Replace L 6a-59
This method determines the solidification point of fatty acids.
Applicable to all fatty acids.
- For titer above 35 C - Use a Griffin low form beaker, 2 liter capacity,
and wide mouth bottle capacity 4 50 mL, height 190 mm and inside diameter
of neck 38 mm. Assemble as shown in illustration in AOCS Official Method
- For a titer of
35 C and below - See illustration in AOCS Official Method Cc 12-59 for
details. A glass beaker may be used instead of stainless steel, if it
is desired to observe the sample during the test. In this case, the
5800 mL and 8000 mL stainless steel beakers with the ground cork insulation
between them may be replaced with a single 8000 mL glass beaker.
- Test tubes, length
100 mm, diameter 25 mm with or without rim. These tubes may have an
etched mark extending around the tube at a distance of 57 mm from the
bottom to show the height to which the tube is to be filled (see Notes,
- Stirrer, 2 to
3 mm outside diameter, with one end bent in the form of a loop of 19
mm outside diameter. Glass, nichrome, stainless steel, or monel wire
may be used. The upper end can be formed to accommodate hand stirring
or attached to a mechanical stirrer (see Notes, 2).
- Laboratory thermometer,
- Titer test thermometer,
AOCS Specification H 6-40. This thermometer should be calibrated against
a National Bureau of Standards certified thermometer (see AOCS thermometer
specifications. If titer is between 68 and 80 C, thermometer H 7-45
should be used.
- Ethylene glycol.
- Dry ice (solid carbon dioxide).
- Heat the fatty acids on a hot plate to 130 C to remove traces of
moisture, and fill a titer test tube to a height of 57 mm from the bottom.
The sample is not held at 130 C nor reheated to this temperature more
than once. If excessive moisture is present, allow the water to settle,
decant the fatty acids and then refilter and reheat. The acids must
be dry and free of suspended matter.
- For titer above
35 C - Fill the water bath to the designated level (see illustration
in AOCS Official Method Cc 12-59) and adjust the temperature 15 to 20
C below the expected titer point.
- For titer 35 C
and below - Fill the bath with ethylene glycol to the designated level.
Insert the stainless steel screen and place dry ice just beneath the
ethylene level (see illustration in AOCS Official Method Cc 12-59 for
details). Crush the dry ice to about 0.5 inch cubes and add slowly and
cautiously to reach the desired temperature. Maintain the temperature
of the bath at 15 to 20 C below the titer point of the sample.
- Place the tube
containing the fatty acids in the assembly, as shown in the illustration
in method Cc 12-59. Insert the titer thermometer to the immersion mark
so that it will be equidistant from the sides of the tube.
- Stir with the
stirring rod in a vertical manner at the rate of 100 complete up and
down motions per minute. The stirrer should move through a vertical
distance of about 38 mm. The agitation is started while the temperature
is at least 10 C above the titer point.
- Stir at the directed
rate until the temperature remains constant for 30 seconds, or begins
to rise in less than 30 second interval. Discontinue stirring immediately,
remove the stirrer or raise it out of the sample, and observe the increase
in temperature. The titer point is the highest temperature indicated
by the thermometer, during this rise. Duplicate determinations are usually
expected to agree within 0.2 C.
Acids Soybean Linseed
Two single determinations performed in 1 laboratory shall not differ
from the mean value by more than:
Single determinations performed in different laboratories shall
not differ from the mean value by more than:
- Titer test tubes
may be obtained from Fisher Scientific, catalog number 14-963A.
- Stirring may be
performed mechanically by attaching a small motor with suitable speed
reducing mechanism to the stirring rod.