MIL-DTL-46225D
4.6.2.3 Solubility in water. Mix the wet sample thoroughly, air-dry a portion on a
Buchner funnel, and transfer approximately 5 grams of the damp material to a tared, filtering
crucible. Heat the crucible and contents in an oven maintained at 65-70 degrees Celsius (C) to
constant weight but not more than 25 hours, cool in a desiccator, and weigh. Wash the dry lead
azide with five 10 mL portions of distilled water at 0 degrees to 15 degrees C, allowing each
portion to remain in contact with the lead azide for three minutes. Catch the filtrate in a clean
filtering flask and retain for determination described in 4.6.2.6. Aspirate for five minutes. Dry
the crucible and contents in an oven maintained at 65-70 degrees C, to constant weight but for no
more than 25 hours, cool in a desiccator and weigh. Calculate the loss in weight of the lead azide
to percent solubility of the sample in water, on a moisture-free basis.
4.6.2.4 Matter insoluble in nitric acid. (see 6.8.3 for precaution) Mix the wet sample
thoroughly, air-dry a portion on a Buchner funnel and transfer approximately 5 g of the damp
material to a tared 150 mL beaker. Heat the beaker and contents in an oven maintained at 65-70
degrees C to constant weight but for not more than 25 hours, cool in a desiccator, and weigh.
Add 100 mL of dilute nitric acid (1:4) to the beaker, and warm beaker with contents on a hot
water bath. (A steam bath or moderately heating hot plate may be substituted. Do not let the
solution boil down to dryness.) Allow any insoluble matter present to settle and decant
supernatant liquid through a tared, filtering crucible (a Gooch crucible fitted with 934AH filter
mats or equivalent may be substituted), catching the filtrate in a clean filtering flask. Repeat the
previous operation (adding 100 mL of dilute nitric acid, warming on a hot bath and filtering) two
additional times. Transfer quantitatively the residue in the beaker to the tared filtering crucible
with the aid of distilled or deionized water. Remove tared, filtering crucible from filtering flask
and attach to another filtering flask (save filtrate for determination described in 4.6.2.5.
Simultaneously prepare an acid blank solution using the same amount of acid used in this
section.) Wash contents of crucible with five 20 mL portions of five percent sodium hydroxide,
allowing each portion of the sodium hydroxide to remain in contact with the residue for 1
minute. Wash crucible and contents with three 20 mL portions of cold (0-15 °C), distilled or
deionized water. Aspirate for five minutes. Dry the crucible and contents in an oven maintained
at 105 degrees C plus or minus 5 degrees C for 1 hour, cool in a desiccator and weigh. Convert
the gain in weight of the crucible to percent insoluble matter in nitric acid.
4.6.2.5 Iron and copper.
4.6.2.5.1 Solution for iron and copper determination. Use commercially available 1000
ppm copper and iron Atomic Absorption (AA) standards. Pipet 1 ml of each into a 100 mL
volumetric flask, fill to volume with deionized water and mix thoroughly. This solution is now
10 ppm in both copper and iron. Store this solution in a plastic bottle.
4.6.2.5.2 Sample preparation. Warm the filtrate reserved from 4.6.2.4 and slowly add 40
mL of 4N sulfuric acid. Do the same to the acid blank solution from 4.6.2.4. Allow the solution
to digest on a steam bath or moderately heated hot plate for 1 hr. Treat the acid blank solution
the same way. Filter the sample solution through a filtering crucible (or a Gooch crucible fitted
with 934AH filtering mats or equivalent) catching the filtrate in a clean filtering flask. Transfer
the filtrate to a clean 250 mL beaker and evaporate the contents to fuming on a hot plate.
Continue the evaporation until approximately 1 mL remains. Allow the residue to cool and add
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