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|  MIL-D-70603(AR)
minute. Finally wash the residue with water, saturated with
antimony sulfide, until the washings come through clear. Reserve
the crucible and residue for the tetracene determination. Transfer
the filtrate and washings quantitatively to a 250 ml. calibrated
volumetric flask, washing the beaker thoroughly with distilled water
and dilute to the mark with distilled water. Using a calibrated
pipette, transfer a 2 ml. aliquot of this solution to a second 100
ml. calibrated volumetric flask and "dilute to the mark with
distilled water. Transfer a portion of this solution to a corex
glass spectrophotometric cell having a width of approximately 1 cm.
and determine its absorbance density at a wave length of 410
millimicrons . Use as a reference, a similar cell containing
ammonium acetate solution of the same concentration as the sample in
the final dilution. Since the cell which holds the normal lead
styphnate is not identical with the reference cell, correct the
absorbance density obtained as described above for the difference in
the amount of light which the two cells scatter and absorb. To do
this, fill both cells with ammonium acetate solution and measure at
a wave length of 410 millimicrons, the absorbance density of the
cell which originally contained the normal lead styphnate solution.
Calculate the percentage of normal lead styphnate in the sample on a
dry basis as follows:
F{A-B)
Normal lead styphnater percent =
WD
Where:
A = optical density of normal lead styphnate solution.
B = optical density of ammonium acetate solution.
D = width of corex cell, cm.
w = weight of the dried sample.
F = factor to be determined for each instrument on the
basis of a sample of lead styphnate that is suitable for use as a
standard. .
4.5.4.4 Tetracene. The wet residue obtained in the
determination of lead styphnate shall be washed three times with
alcohol, dried in an oven maintained at 60C. plus or minus 5C
for 30 minutes, cooled in a desiccator and weighed. The dried
residue in the crucible shall be transferred to a 125 ml. beaker
with a stream of water, 25 ml. of water shall be added, and the
contents of the beaker boiled on a hot plate for 5 minutes. The
contents of the beaker shall be poured into the same crucible, and
the residue in the crucible washed three times with boiling water,
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