MIL-DTL-23938B(AS)
(mL = milliliters of potassium dichromate)
4.5.1.3 Alternate procedure.
a. Weigh a 0.5 gram sample to the nearest 0.1 mg in a 250 mL beaker.
b. Add 25 mL of distilled water and 15 mL of concentrated hydrochloric acid. Heat until the
sample is completely dissolved.
c. Transfer to a 250 mL volumetric flask. Wash the beaker carefully with 5 portions of
distilled water. Add the washings to the volumetric flask. Make up to volume with distilled water.
d. Pipette a 25 mL aliquot into a 250 mL beaker. Acidify the solution by addition of 5 mL
of concentrated HCl.
e. Add 30 mL of freshly prepared 6 percent aqueous solution of cupferron (ammonium
N-nitrosophenylhydroxylamine). Do not allow the solution and the precipitate to get warm. Cold
precipitation (about 50 °F) is preferred.
f. Filter through a Munktell No. 00H or equivalent filter paper. Wash the precipitate
with dilute hydrochloric acid solution.
g. Transfer the filter paper containing the precipitate into a pre-ignited and weighed
porcelain crucible.
h. Dry in an oven before ignition. Ignite the material at first on a burner and then place in a
muffle furnace, set at 1450 ±50 °F, for 30 minutes.
i. Cool in a desiccator and weigh.
j. Calculate as follows:
B-A
X 100
percent Fe2O3 =
W
where:
A = weight of crucible
B = weight of crucible plus precipitate
W = weight of sample
4.5.2 Determination of volatiles. The determination of volatiles shall be as follows:
a. Weigh, to the nearest 0.1 mg, 2 clean, dry (l hour at 220 °F), stoppered weighing bottles
and record weights as A.
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