MIL-DTL-398D
N = Normality of NaOH solution used.
W = weight of sample, dry basis
4.7.6 Determination of granulation. A 50 + 0.05 gram sample
of RDX (dry weight), weighed accurately to the nearest 0.01 gram,
shall be transferred to a 600 ml beaker containing approximately
300 ml of a 2 percent solution of a suitable wetting agent such
as dioctyl sodium sulfosuccinate (see 6.5). With the aid of a
rubber policeman attached to a glass stirring rod, the mixture
shall be stirred for a few minutes wetting the sample thoroughly
and breaking up as many of the aggregates as possible.
a. A spray nozzle (see 6.7) under tap water pressure, shall
be used to quantitatively transfer this mixture to the uppermost
sieve of a set of the specified 8-inch U.S. Standards sieves
complying with Specification RR-S-366, nested in order of
decreasing size, the largest mesh being placed on top. This
assembly should be set up near a water tap and drain. Provision
should be made to prevent transfer of the explosive to the drain.
The pressure of the spray shall be adjusted so that when the
spray strikes the sample at an angle approximately perpendicular
to the screen from a height of 2 to 3 inches, it is possible to
wash the sample back and forth across the sieve without splashing
any of the material over the side of the sieve. The spray should
be moved about the screen at a rate such that the spray would
traverse the diameter of the screen 1 to 2 times per second. The
wet agglomerates shall be gently crushed on the top sieve with
the aid of a rubber policeman and the washing of the material
back and forth across the sieve with the water spray shall be
continued until all the agglomerates have been broken and only
individual crystals larger than the mesh of the sieve remain on
the sieve. The rubber policeman shall be used in breaking up the
agglomerates on only the uppermost sieve. The top sieve shall be
removed and a few drops of a 10 percent solution of the wetting
agent shall be added to the material on the next sieve and washed
with the water spray as before for a maximum of 2 minutes or
until no change is noticed in the amount of crystals remaining.
This procedure shall be repeated for each of the sieves.
b. After the washing has been completed, the portions
remaining on each of the screens shall be quantitatively
transferred by means of a suitable transfer funnel into a
separate previously tared fritted glass filtering crucible of
coarse porosity as follows: The screen shall be held in an
almost vertical position and with a moderate spray of water from
the spray nozzle, the material shall be gently washed to the
lower part of the screen by drawing the spray back and forth
across the screen, beginning at the top and moving slowly down
the screen as the crystals move down. When the material has been
collected at the lower part of the sieve, it can readily be
washed into the crucible with a stream of water from a wash
bottle.
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