MIL-PRF-87896A
4.5.4.1.3 Procedure.
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4.5.4.1.3.1 Calibration curve. Prepare a working standard by adding 100 mL of the 10 M F
solution to 100 mL of buffer solution. Prepare a blank containing 50 mL of 0.2 N NaOH and 50.0 mL
buffer solution in a plastic beaker. Place a reference electrode (single junction type) and a fluoride ion
selective electrode, connected to a millivolt meter (0.1 mV scale), into the blank. Gently stir the blank and
record the mV reading when the reading becomes stable. Successively add increments of the working
standard to the blank to generate a calibration curve. Record stable mV reading after each addition.
4.5.4.1.3.2 Sample preparation. Place 50 mL of 0.2 N NaOH solution into each of two PTFE
bubblers connected in series. Establish a flow of < 1000 sccm of the propellant through the bubblers
using a suitable flow controller or flow meter. Continue the flow of propellant through the bubblers until
approximately 15 liters (at STP) of the propellant has been sparged through the 0.2 N NaOH solution.
Transfer the contents of each bubbler to separate 100 mL volumetric flasks and add 50 mL of the buffer
solution to each. If necessary, fill to the mark with de-ionized or distilled water.
4.5.4.1.3.3 Measurement. Transfer the contents of the volumetric flasks prepared in 4.5.4.1.3.2
into separate plastic beakers. Place the electrodes into each beaker and record the mV readings for
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each in the same manner as for the blank. Determine the F concentration using the calibration curve
generated in 4.5.4.1.3.1.
4.5.4.1.3.4 Calculation. Calculate the concentration of total reactive fluorides as HF in the
propellant using the equation below. The HF concentration of the second bubbler should be insignificant
compared to the first bubbler. If significant HF levels are found in the second bubbler, prepare a new
22.4 �/����
sample with a lower flow rate.
� × 100
����� �������� ��������� �� �� (���%) = � × 0.11 × �
��
where,
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C
=
F concentration (M) determined in 4.5.4.1.3.3.
Vs
=
Volume of propellant sampled (liters at STP).
4.5.4.2 Fourier Transform Infrared Spectroscopy (FTIR). Determine the HF content on an FTIR
spectrometer that has been validated and calibrated for an HF concentration of approximately 0.05% vol.
4.5.5 Water. The concentration of water in the propellant is determined by one of the following
methods. In case of dispute the electrolytic method in 4.5.5.1 shall be the referee method.
4.5.5.1 Electrolytic. Connect the sample container to a pressure regulator that is attached to an
electrolytic moisture apparatus (hygrometer). Open the sample container valve and adjust the pressure
to the apparatus in accordance with the manufacturer's recommended value. Allow sufficient time for the
indicated moisture content to become stable and read the value obtained while using the most sensitive
scale setting possible for the moisture content of the sample. The hygrometer should be set on a range
no greater than ten times the specified maximum moisture content.
4.5.5.2 Piezoelectric. Determine the moisture content utilizing a piezoelectric sorption
hygrometer that is set on a range no greater than ten times the specified maximum moisture content by
following the instrument manufacturer's instructions.
5. PACKAGING
5.1 Packaging. For acquisition purposes, the packaging requirements shall be as specified in
the contract or order (see 6.2). When actual packaging of materiel is to be performed by DoD or in-house
contractor personnel, these personnel need to contact the responsible packaging activity to ascertain
packaging requirements. Packaging requirements are maintained by the Inventory Control Point's
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