FED-STD-791D
b. Immerse in dilute nitric acid solution for 15 1 s.
c. Rinse the silver strip only in hot 82 to 100C (180 to 212F) tap water, and
then wet polish with pumice. (No polishing of the copper strip is required.)
d. Rinse the strip in hot tap water, and then in hot distilled water.
e. Dip in acetone, and allow to air dry.
6.3 Handling the strips with tongs, weigh each strip to the nearest 0.1 mg.
CAUTION:
In succeeding steps the strips must be handled only with tongs until
after they have been weighed (see 6.9) at the end of the test.
6.4 Mount each strip in a glass support then place each support in a separate
beaker so that the strip does not touch the sides of the beaker.
6.5 Add 200 mL of the sample to each beaker, and cover with watch glass to
avoid evaporation losses.
6.6 Store both beakers in an oven for 50 h at 232 3C (450 5F).
6.7 At the end of the heating period, remove both beakers from the oven and
allow them to cool to room temperature.
6.8 Remove the copper and silver strips from the supports and clean them as
follows:
a. Wash each strip with successive portions of fresh, hot 60C (approx. 140F)
1,1,1-trichloroethane, to remove as much discoloration and deposit as
practicable.
b. If carbonaceous deposits remain, place the strip (as a cathode) in the electrolytic
bath for 10 min at 0.5 A.
c. Wash each strip in hot, running water, while rubbing it with an eraser.
d. Rinse each strip with distilled water, then with acetone, and air dry both strips.
6.9 Weigh each strip to the nearest 0.1 mg, and compute the change in weight of
each strip (see 7.1).
6.10 Measure the surface area of each strip (both sides) (see 7.1).
7. CALCULATIONS
7.1 The calculations to determine mg/cm2 as follows
-
CW = W 1 W 2
2*W * L
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