MIL-DTL-14067C
precipitate remains only moist enough to prevent cracking. This procedure shall be
repeated 7 times finally washing with two 10 milliliter portions of cold distilled water.
n. The precipitate shall be dried to constant weight in an oven at 155o to 160oC, cooled in a
dessicator, and weighed.
The percent magnesium shall be calculated as follows:
Percent magnesium =
Where:
A = grams of precipitate.
W = grams of sample contained in the aliquot.
4.5.16.2 Magnesium (alternate method).
4.5.16.2.1 Reagents.
a.
Chromic acid solution (approximately 0.1 N as acid). Dissolve 10.00 grams of CrO3 in
distilled water and dilute to 1000 milliliters (mL).
Magnesium standard solution Dissolve 1.8 grams of pure magnesium in 125 milliliters
b.
of 1:4 hydrochloric acid. Dilute to 1000 milliliters in a volumetric flask with distilled
water. (One milliliter contains approximately 1.8 milligrams of magnesium). WA =
Actual weight of magnesium used in grams.
EDTA reagent solution Dissolve 40.0 grams of disodium dihydrogen
c.
ethylenediaminetetracacetate dihydrate in distilled water and dilute with distilled water to
1000 milliliters in a volumetric flask.
Buffer solution (approximately pH 10) Dissolve 65.5 grams of reagent grade
d.
ammonium chloride in 300 milliliters of distilled water. Add 570 milliliters of
concentrated (28-30 % w/w) ammonium hydroxide and dilute to 1000 milliliters with
distilled water.
Eriochrome Black T indicator solution Dissolve 0.8 grams of Eriochrome Black T in a
e.
mixture of 40 milliliters methanol and 60 milliliters of triethanolamine.
4.5.16.2.2 Standardization.
a. Pipette 50.00 milliliters of magnesium standard into a 600 milliliter flask. Dilute to about
300 milliliters with distilled water.
b. Add 20 milliliters of buffer solution and 6 -10 drops of Eriochrome Black T indicator.
Titrate with EDTA to a color change of red to blue against a reflected light background.
There should be no red color remaining. VA = Volume of EDTA used in milliliters.
X = Milligrams of magnesium per milliliter EDTA =
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