MIL-PRF-23950B(AS)
determination of purity, which is given below. The standardization factor, in milligrams (mg) of
aluminum (Al), is calculated as follows:
mL of Aluminum aliquot X sample weight of Aluminum
mg Al =
1,000
mg of Aluminum
Standardization factor =
mL of standard acid
4.4.2.1.3 Procedure.
a. Weigh 0.25 g of sample to the nearest 0.1 mg.
b. Transfer the sample to the 250-mL beaker and carefully add 10 mL of 25 percent NaOH.
Cover the beaker immediately with a watch glass to prevent any loss due to spattering.
c. After initial reaction has ceased, heat the solution to boiling on a hot plate.
d. Cool to room temperature. Wash the watch glass with three portions of distilled water,
collecting the washings in the original beaker.
e. Transfer the solution analytically to a 250-mL volumetric flask and make up to the mark
with distilled water.
f. Pipette 20 or 25 mL of aliquot into a 250-mL beaker. Add 100 mL of distilled water.
g. Prepare the titrator by filling the buret with the standard HCl solution and turning the
instrument on. Set the pH dial to 10.5 and the acid-base switch to set. Turn the selector switch
to neutral and the millivolt (mV)-pH switch to pH.
h. Place the beaker containing the sample on the stand and raise the stand so that the
electrodes and stirrer are in the solution and the safety switch is activated. Turn the selector
switch so that the titrator delivery unit is connected with the rest of the apparatus.
i. Adjust the pH of the solution to just above 10.5 with the aid of strong NaOH and HCl
solutions. Set the acid-base switch to base and allow the titration with dilute standard acid to
bring the pH of the solution to exactly 10.5.
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