MIL-DTL-757C
4.4.7 Acidity. Transfer approximately 1 g of the dry sample weighed to the nearest 1 mg
to a 150 mL beaker. Add 100 mL of freshly boiled and cooled distilled water having a pH of 6.0
± 0.5 and allow the mixture to stand with occasional stirring for 15 minutes. Filter and determine
the pH of the filtrate at 25° ± 2°C by means of a pH meter that is capable of measuring pH within
0.1 pH unit. The pH meter shall have glass and calomel electrodes and shall be calibrated with
standard buffer solution. Test another 100 mL portion of the water concurrently with the sample
solution and correct the pH of the sample solution for any change in pH found in this blank
solution.
4.4.7.1 Acidity (alternate method). Transfer approximately 50 mL of the water covering
the sample obtained in 4.3.3.1 to a 200 mL beaker. Determine the pH value of this solution in
accordance with method given in ASTM E70.
4.4.8 Material insoluble in ammonium acetate. Transfer approximately 1 g of the dry
sample, weighed to the nearest 1 mg, to a 250 mL beaker. Add 100 mL of distilled water and
then add slowly with constant stirring 100 mL of 20 percent ammonium acetate solution. Stir
frequently for 15 minutes and filter the solution through a tared sintered-glass crucible of fine
porosity. Transfer the residue to the crucible with distilled water and wash the crucible with
distilled water until the washings are colorless. Dry in an oven at 100°C to 105°C for 1 hour,
cool in a desiccator, and weigh. Calculate the percent material insoluble in ammonium acetate as
follows:
100 A
Percent material insoluble in ammonium acetate =
W
where: A = weight of residue, g
W = weight of sample, g
4.4.9 Material soluble in ether. Transfer approximately 2 g of the dry sample weighed to
the nearest 1 mg to a 150 mL beaker, add 50 mL of anhydrous ethyl ether and allow to stand
with occasional stirring for about 15 minutes. Filter through a dry No. 40 Whatman filter paper
or equivalent and catch the filtrate in a tared 100 mL beaker. Wash with a total of 20 mL of
ether. Evaporate off the ether in the 100 mL beaker on a steam bath or by means of a current of
dry air. Place in a vacuum desiccator containing sulfuric acid until constant weight to the nearest
0.1 mg is obtained. Run a blank determination of 70 mL of ether. Calculate the percent material
soluble in ether as follows:
100( A - B)
Percent material soluble in ether =
W
where: A = weight of residue from sample, g
B = weight of residue from blank, g
W = weight of sample, g
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