MIL-DTL-11751G
4.5.9 Ammonium hydroxide precipitate. Cautiously add 12 mL of sulfuric acid to 12 mL
of water, cool, add the mixture to 100 mL of solution "A" prepared in 4.5.5, and evaporate to
dense fumes. Cool, dissolve the residue in 130 mL of hot water, and add ammonium hydroxide
until the solution is just alkaline to methyl red. Heat to boiling, filter, wash with hot water, and
ignite. Calculate the percent by weight ammonium hydroxide precipitate as follows:
Percent ammonium hydroxide precipitate = 100 x A
W
where: A = Weight of residue in grams.
W = Weight of specimen in grams.
4.5.10 Heavy metals. To 30 mL of solution "A" prepared in 4.5.5, cautiously add 15 mL
of nitric acid. Prepare a control by adding 0.04 mg of silver ion to 10 mL of solution "A" and
cautiously adding 15 mL of nitric acid. Evaporate both solutions to dryness over a low flame or
on an electric hot plate. Dissolve each residue in about 20 mL with water. Adjust the pH of
each solution to between 3 and 4 (using a pH meter) with 1 N acetic acid or ammonium
hydroxide solution containing 10 percent ammonia. Dilute to 40 mL with water and mix. Add
10 mL of freshly prepared hydrogen sulfide water to each and mix. Any yellowish brown color
produced in the specimen solution shall be no darker than that produced in the control.
4.5.11 Iron. Neutralize 20 mL of solution "A" prepared in 4.5.5 with hydrochloric acid
using phenolphthalein indicator. Add 2 mL of hydrochloric acid in excess and dilute to 50 mL
with water. Prepare a control by adding 0.01 mg of iron and 2 mL of hydrochloric acid to the
residue obtained from evaporation of the quantity of hydrochloric acid used to neutralize the
specimen solution. Dilute to 50 mL with water. To each solution, add 30 to 50 mg of
ammonium persulfate and 3 mL of 30 percent ammonium thiocyanate solution. Any red color
produced in the specimen solution shall be no darker than that produced in the control.
4.5.12 Sodium.
4.5.12.1 Flame photometer. Use a flame photometer that will accurately determine the
amount of sodium in the specimen.
4.5.12.2 Control solution. To 10 mL of solution "A", add 0.2 mg of sodium ion and
dilute to 100 mL with water.
4.5.12.3 Specimen solution. Dilute 10 mL of solution "A" prepared in 4.5.5 to 100 mL
with water.
4.5.12.4 Procedure. Adjust the flame photometer to give the maximum emission with
the control solution prepared in 4.5.12.2 at the 589 nanometer (nm) sodium line and note this
reading. Without adjusting the flame photometer's controls, determine the emission of the
specimen solution prepared in 4.5.12.3 at this wavelength. Change only the monochromator by
the amount specified in this test. Observe the emission of the control solution prepared in
4.5.12.2 at 589 nm sodium line. Observe the emission of the specimen solution prepared in
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