MIL-DTL-248D
4.4.5 Alkalinity. The specimen shall be considered unsatisfactory with respect to
alkalinity when B is greater than A in the calculations under "Acidity", para. 4.4.4.
4.4.6 Insoluble matter. The insoluble matter shall be determined in accordance with
MIL-STD-650, Method 105.1 using methylene chloride as the solvent. Furthermore, the residue
in the filtering crucible shall be dried in an oven at 100 ± 5°C
4.4.7 Sodium.
4.4.7.1 Atomic absorption spectrophotometric methods for the determination of sodium.
4.4.7.1.1 Apparatus. Any satisfactory Flame (FAA) or Graphite Furnace Atomic
Absorption (GFAA) Spectrophotometer
4.4.7.1.2 Reagents. Reagent Grade ACS sodium chloride and sodium- free distilled
water shall be used. All references in this method to distilled water means sodium- free distilled
water.
4.4.7.1.3 Preparation of sodium standard solutions.
4.4.7.1.3.1 Stock solution prepared from sodium chloride preparation. Accurately
weigh 127 mg of reagent grade sodium chloride (or equivalent of other suitable sodium standard)
to the nearest 0.1 mg on an analytical balance and transfer to a clean dry 1000 ml volumetric
flask. Dissolve in sodium- free distilled water and make up to the mark. This solution contains
approximately 50 parts per million of sodium. Calculate exact concentration.
AW Na
WNaSample = WNaCl ×
MWNaCl
Where:
WNaSample = mg Na in Sample
WNaCl = mg NaCl used
AW = Atomic Weight of Na (23)
MW = MolecluarWeight of NaCl ( 58)
Initial ppm may be expressed as:
WNa
C Na1 =
×1000
Vtotal
4.4.7.1.3.2 Alternate stock solution. Prepare a 50 ppm sodium stock standard from a
commercially available certified sodium standard.
4.4.7.1.3.3 Stock solution prepared from sodium chloride (for GFAA). Transfer a 10 ml
aliquot of the Stock Solution from 4.4.7.1.3.1 or 4.4.7.1.3.2 (above) from the 1000 ml
volumetric flask into another 1000 ml volumetric flask and dilute to the mark with sodium- free
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