FED-STD-791D
6.5.2 Polish each square with the 240 grit paper to remove any marks produced
by coarser abrasive. Store squares immersed in separate containers of acetone until ready
for final polishing.
NOTE 5:
Caution. Acetone is flammable. Use only in a well ventilated area. Keep
all flames away from acetone.
6.5.3 Remove each square from the acetone, and final polish both sides to a
mirror finish, using 150 mesh silicon carbide grit (held on an acetone-moistened cotton
pad).
6.5.4 Clean all metal dust from the square by rubbing vigorously with clean pads
of absorbent cotton until a fresh pad remains unsoiled.
6.6 Continue preparation of all five squares as follows:
6.6.1 Wash squares in warm 1,1,1-trichloroethane (approximately 54C [130F]),
rinse with 1,1,1-trichloroethane, and allow them to air-dry.
NOTE 6:
Caution. 1,1,1-Trichloroethane is toxic. Do not breathe its fumes nor
allow it to come in contact with the skin.
6.6.2 Immediately weigh each square to within 0.1 mg.
6.6.3 Arrange squares in the wooden assembly fixture in the pattern shown in
Figure l, making certain that the magnesium and copper squares do not touch each other.
(When testing spindle oil, the metal squares shall be placed in the test tube in such a
manner as to form a "V" in the bottom of the test tube.)
6.6.4 Using only forceps to handle the clean cord, tie the squares together as
shown in Figure 1.
6.7 Prepare new test set up as follows:
6.7.1 Insert the tied metal squares in the test tube, positioning the squares
vertically (so that the air tube can be inserted to touch the bottom of the test tube).
Weigh the air tube, test tube, and contents together to within 0.1 g.
6.7.2 Add 100 l mL of sample to the test tube, reweigh the air tube, test tube,
and contents together to within 0.1 g, and determine weight of sample added.
6.7.3 Assemble the test tube and condenser and mount the assembly so that 30
5 cm of test tube is submerged in the bath operating at specified temperature.
6.7.4 Start the flow of cooling water through the condenser jacket.
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