MIL-DTL-398D
4.7.1.3 Report. If the mercury column is completely
immersed at the melting point temperature, this temperature shall
be reported with calibration corrections applied, as the melting
point of the sample. If part of the column is exposed, the
following correction shall be added to the observed temperature:
Correction = n (T-t) 0.000159
Where:
n = number of degrees C. in the exposed mercury column.
T = uncorrected melting point in degrees C.
t = average temperature in degrees C. of the exposed mercury
column.
4.7.1.4 Alternate method. The Fischer-Johns hot stage
melting point apparatus shall be used as an alternate method to
determine the melting point of RDX. The thermometer of this
apparatus shall be calibrated using appropriate melting point
standards. A portion of the sample shall be ground in small
agate mortar and a very small quantity (approximately 0.05 gram)
of the finely pulverized sample placed between two clean 18
millimeters (mm) diameter cover glasses. These shall be gently
but firmly pressed together and placed in the circular depression
on the stage. The powerstat shall be turned up and the unit
allowed to heat. The heating rate may be very rapid to within 15
degrees C of the melting point. Thereafter a heating rate of
approximately 1 degree C per minute shall be used. When the
sample begins to melt, the thermometer shall be read and the
temperature reading adjusted to reflect the thermometer
calibration correction shall be reported as the melting point.
4.7.2 Determination of insoluble particles. A 50 gm + 0.5
gm portion of the sample shall be weighed to the nearest 0.01
gram in a 600 ml beaker. Three-hundred ml. of acetone shall be
added and the beaker and contents heated on a steam bath until
all lumps are broken down and all soluble material is dissolved.
The mixture shall be poured through a small U.S. Standard No. 60
sieve. Care shall be taken to wash all the insoluble matter from
the beaker with acetone. The residue in the sieve shall then be
washed with acetone to remove the RDX. The particles retained
shall be counted. Sieve shall comply with the requirements of
Specification RR-S-366. The residue from the sieves and the
filtrate may be retained for acetone insoluble and inorganic
insoluble analysis in 4.7.3 and 4.7.4 respectively.
4.7.3 Acetone insoluble material. Use the residue and
filtrate from 4.7.2 or weigh an approximate 10 gram portion of
the dried sample accurately to the nearest 0.01 gram, place the
sample in a 400 ml beaker and add 200 ml of filtered acetone.
Place the beaker and contents on a steam bath (cover with a watch
glass if necessary) and stir occasionally until all of the RDX
has dissolved. Filter the RDX solution through a 25 ml medium
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