MIL-DTL-398D
4.6.2 Inspection equipment. Commercially available
inspection equipment shall be used for all examinations and tests
specified in 4.5 and 4.7. The contractor is responsible to have
the necessary equipment available, use it correctly and to assure
that proper calibration procedures are followed. The designation
of an instrument of a particular make or model number is not
intended to preclude the use of an equivalent make or model which
is capable of performing the required test. Government approval
of all inspection equipment is required prior to its use for
acceptance purposes. Inspection equipment designs shall be
submitted to the Technical Agency (see 6.12).
4.7 Methods of inspection. The following tests shall be
performed using prescribed analytical procedures for replicate
determination given in standard and analytical textbooks. Also,
unless otherwise specified herein, all chemicals and reagents
shall be ACS Grade or reagent grade chemicals (see 6.13 for use
of equivalent test methods).
4.7.1
Determination of melting point.
4.7.1.1 Apparatus. A melting point bath equipped with a
mechanical stirrer and a source of heat that can be easily
regulated shall be set up. A beaker of 1 to 2 liters capacity
about 3/4 full of clear paraffin oil is suitable. An accurately
standardized total immersion Centigrade (C.) thermometer shall be
suspended in the bath so that the bulb is not less than 1.5
inches from the bottom of the bath. If the mercury column is not
completely immersed at the temperature of the observed melting, a
second thermometer shall be suspended about 0.5 inch from the
first thermometer with its bulb approximately at the height of
the middle of the exposed mercury column of the first
thermometer.
4.7.1.2 Procedure. A thin-walled capillary tube of uniform
diameter, long enough to extend beyond the top of the bath shall
be used. The tube shall be filled with a dry portion of the
sample to a depth of approximately 4 millimeters (mm), the sample
compacted by tapping, and the tube fastened to the standardized
thermometer so that the lower end of the tube is in contact with
the bulb of the thermometer. The stirrer shall be started and
the bath heated rapidly to approximately 180 degrees C., then
gradually heated so that the rise in temperature is not less than
1 degree in 3 minutes nor more than 1 degree in 1 minute. Since
RDX does not melt sharply or give a definite meniscus, the
melting point of the material shall be observed at the point at
which the sample first gives evidence of movement in the
capillary, exclusive of shriveling. There is an increase in
volume caused by decomposition and evolution of gas. This is
especially marked with Type II. The beginning of gas evolution
causes the sample to rise slowly in the capillary. The
temperature at which this occurs shall be taken as the melting
point.
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