MIL-PRF-23950B(AS)
b. Fit the flask with an Allihn condenser or equal and reflux for one hour using a heating
mantle. Caution: Protect from open flames or sparks.
c. Remove the round bottom flask and filter the ether through filter paper into a Claissen
flask or equal. Attach a West condenser and adapter, or equal, to the flask. The West
condenser and adapter shall enter a second Claissen flask. The second Claissen flask shall be
vented by means of rubber tubing or equal.
d. Distill the ether until there is only about 50 to 75 mL of ether left in the flask.
e. Pour the remaining ether into a tared 150-mL beaker and evaporate over a steam bath in a
vented hood.
f. When dry, place the beaker in a 110°C (230°F) oven for one hour. Cool in a desiccator
and weigh.
g. Calculate as follows:
Weight of residue in grams
percent Ether extractable = X 100
Weight of sample in grams
4.4.2.3.2 Alternate procedure.
a. Weigh a sample of the material, to the nearest mg in a Whatman filter thimble. Choose
the sample size so that the thimble is filled to within 10 mm of the rim.
b. Place the thimble in a siphon cup. Attach the cup of the cooling coil of the underwriters
extraction apparatus.
c. Add 70 mL of the ether in the 400-mL extraction flask and assemble the apparatus as
shown in figure 1.
d. Heat the flask on an electric hot plate, or equal, at low temperature. Turn on the cooling
water and extract the material for two hours in this manner.
e. Cool, remove the thimble from the cup and reassemble the unit. The excess ether may
now be distilled off in the siphon cup and removed when the cup is one-half full. Distill in this
manner until about 15 to 20 mL of the liquid remains in the flask.
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