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| MIL-L-14758 (MU)
4.3.3.1 Standard method
4.3.3.1.1 Apparatus. -Assemble the apparatus as shown on
Figure 1. Insert the burette, containing water saturated with
nitrogen, into one hole in the rubber stopper of the reaction
flask. Add 90 ml. of 10 percent sodium hydroxide solution
saturated with nitrogen, to the 125 ml. carbon dioxide absorption
flask. Fill the gas burette and leveling bulb with a 0.1 percent
solution of Nacconol, or approved equivalent, saturated with
Control the temperature of the system by circulating
nitrogen.
water by means of a pump, between the water reservoir which
serves as a jacket for the reaction flask and the glass jacket
(NOTE: An equivalent type of apparatus
of the gas burette.
and method may be used (see 6.5).
4.3.3.1.2 Determination. -Air dry part of the sample in a
Buchner funnel and then heat in an oven maintained at 65
degrees Centigrade (degrees C.) to constant weight, but not
(NOTE : An alcohol wash may be used to aid
more than 25 hours.
drying). Transfer an accurately weighed portion of approx-
imately 1.7 gm. of the dried sample to a glass vial shown on
Figure 1. Add 3 ml. of water to the sample and place the vial
containing the sample plus the water erect in the reaction
flask containing 75 ml. of 15 percent ceric ammonium nitrate
solution saturated with nitrogen. Connect the reaction flask
to the apparatus (to insure that the reaction and absorption
flasks are connected to the apparatus without air leaks,
apply a coat of molten paraffin wax to all rubber-to-glass
joints of these assemblies) without disturbing the position
of the vial. Open stopcocks 1 and 2 to the atmosphere
by adjusting them as shown by position A on figure 1. Adjust
the water level in the gas burette to zero with the aid
of the leveling bulb. Allow the system to come to a temperature
equilibrium by waiting 10 minutes after connecting the reaction
flask. Read the temperature of the thermometer in the water
jacket to 0.1 degree C. Turn stopcocks 1 and 2 to position B
and shake the reaction flask so that the vial inside of it is
upset and assumes a horizontal position at the bottom of the
reaction flask. As the gas is evolved from the reaction mixture,
lower the leveling bulb so that the liquid level in the leveling
bulb is slightly below that in the gas burrette. Gently agitate
the reaction flask occasionally, to aid in completing the
decomposition of the lead azide. When all the lead azide has
decomposed, as indicated by the fact that gas bubbles are no
longer forming in the mixture in the reaction flask, fill the
flask with a measured volume of water from the water burette.
Allow the temperature of the system to adjust itself to within
0.1 degree C. of its temperature at the beginning of the
determination and then measure the volume of gas in the gas
burette at the existing atmospheric pressure. Determine the
atmospheric pressure to the nearest 0.1 mm. of mercury with the
aid of a mercurial barometer having a brass scale. Correct the
observed reading to O degrees C. Calculate the percent lead
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