MIL-DTL-53030D
4.5.4.2.2.2.2 Procedure.
a. Accurately weigh 2.000 gram of pigment into a 250 ml glass stoppered
Erlenmeyer flask.
b. Add 25 ml concentrated NH4OH, stopper and shake vigorously every few minutes
over a period of 60 minutes.
c. Add 25 ml H2O and filter through fine paper into a 400 ml beaker, washing well with
water.
d. Neutralize the filtrate with 7.5N HNO3 (requires about 35 ml).
e. Add 15 ml concentrated HNO3 and 6g of NH4NO3. Stir.
f. Heat the clear solution to 176 oF (80 oC) maximum and add 75 ml of ammonium
molybdate with constant stirring.
g. Stir for several minutes and let the precipitate settle for 2 hours.
h. Filter through a tared crucible (Gooch or medium glass), transfer the precipitate, and
wash with 1 percent HNO3 (5 ml concentrated HNO3/500 ml solution). The washing
shall be thorough.
i. Give the collection precipitate a final wash with a small amount of water.
j. Dry the crucible for 2 hours in a 221 oF (105 oC) oven.
k. Cool crucible in a desiccator and determine the weight of the precipitate to the
nearest one-tenth mg (it shall not exceed 3g; if it does, repeat the determination
with a smaller sample).
4.5.4.2.2.2.3 Calculations.
Percent phosphate [PO4] = (weight of precipitate x 5.029) / (Sample weight)
Percent zinc phosphate = (weight of precipitate x 11.18) / (Sample weight)
[Zn3 (PO4)2 · 2H2O]
4.5.4.2.2.2.4 Failure criteria. Nonconformance to table I shall constitute failure of this test.
4.5.4.2.3 Acid insoluble. Determine matter insoluble in acid in the extracted pigment in
accordance with the appropriate test method. Nonconformance to the extender requirement of
table I shall constitute failure of this test.
4.5.4.2.4 Hexavalent chromium. Determine the presence or absence of hexavalent chromium by
either of the following chemical reagent screening techniques.
(a) Weigh approximately 250 mg of pigment into a small glass test tube. Add 5 ml of 25
percent aqueous KOH and shake vigorously for 1 - 2 minutes. Decant a one ml aliquot into a
plastic micro-centrifuge tube and centrifuge for five (5) minutes at 17,000 rpm, balancing the
centrifuge with a tube containing one ml of the KOH solution. The resulting supernatant liquid
shall be nearly colorless. Use the tube containing the KOH solution as a reference. A distinct
yellow color indicates the presence of hexavalent chromium and therefore shall constitute failure
of the test requirement.
(b) Weigh approximately 50 mg of pigment into a small glass test tube. Add 5ml of 10
percent aqueous H2SO4 and shake vigorously for 1 - 2 minutes. Decant a one ml aliquot into a
plastic micro-centrifuge tube and centrifuge for five (5) minutes at 17,000 rpm, balancing the
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