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|  MIL-S-10521K (AR)
4.5.2 Determination of compositions.
4.5.2.1 Match head. Prior to adding the lacquer, a one gram
sample shall be selected and analyzed as follows:
4.5.2.1.1 Antimony sulfide. An accurately weighed portion of
approximately 1 gm shall be transferred to a 150 milliliter (ml)
beaker . Twenty-five ml's of 12N hydrochloric acid shall be added to
the beaker, heated on a steam bath for 30 minutes with occasional
stirring, and then filtered through a tared medium porosity glass
crucible with the aid of suction. The beaker and contents of the
crucible shall be washed with a two percent solution of hydrochloric
acid and finally with four 5 ml. portions of water. The crucible
and contents shall be dried in an oven maintained at 100 + 5C,
212 10F, for one hour, cooled in a desiccator for 15 minutes
and weighed. The percentage of antimony sulfide in the sample shall
be calculated as follows:
Percentage of antimony sulfide = A -
[(B-C) + (DE) x 100
divided by A )]
where:
=
weight of sample
A
B
=
weight of crucible and residue.
weight of crucible.
c
=
=
loss in weight of crucible and contents after extraction
D
with 15N nitric acid as determined in 4.5.2.1.2.
E = factor required by volubility of red phosphorus in
hydrochloric acid (see 4.5.2.1.1.1).
4.5.2.1,1,1 Calculation of factor E. From the red phosphorus
used in the manufacture of the match head composition, 0.5300 plus
or minus 0.001,0 gm. shall be transferred to a 150 ml. beaker and 25
ml. of 12N hydrochloric acid added. The beaker and contents shall
be heated on a steam bath for 30 minutes, stirred occasionally, and
then filtered through a tared, medium porosity glass crucible, with
the aid of suction. The beaker and contents of the crucible shall
be washed with a two percent solution of hydrochloric acid and
finally with four 5 ml portions of water. The crucible and contents
shall be dried in an oven mainatained at 100 + 5C, 212 + 10F,
for one hour, cooled in a desiccator for 15 minutes and weighed.
The loss in weight of the crucible and contents shall be calculated
to percentage of red phosphorus soluble in 12N hydrochloric acid.
The factor represented by the letter E in the equation for
percentage of antimony sulfide shall be calculated as follows:
E = F divided by G
where:
F = percent volubility of the red phosphorus used in the
composition, expressed as a decimal fraction.
G = percent of volubility of the red phosphorus subtracted
from 100 and the results expressed as a decimal fraction.
46
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