MIL --- DTL --- 3668E(EA)
4.4 Tests.
4.4.1 Purity. Prepare and measure the absorbance of a standard 1,4 --- Diamino --- 2,3 --- Dihy-
droanthraquinone dye solution and specimen solution as follows: Weigh to the nearest milli-
gram approximately 0.186g of dye and quantitatively transfer to a 500 --- milliliter (mL)
volumetric flask using small amounts of ethanol for washing. Dissolve specimen in approxi-
mately 400mL of ethanol, stirring and breaking up all lumps to facilitate the solution. Dilute to
500mL with ethanol. Shake thoroughly to insure uniform mixing. Remove a 20mL aliquot,
transfer to a second 500mL volumetric flask, dilute to 500mL with ethanol, and mix thoroughly.
Using a spectrophotometer, read the adsorbance value of the more dilute solution at 456 +/ ---
2 nanometers. Use the ethanol that was used in preparing the solution as the reference liquid
in the spectrophotometer. Calculate the percent purity as follows:
Percent purity = (ABC)∕(DE)
where: A = Percent purity of the standard,
B = Absorbance value of the specimen,
C = Weight of standard in grams (gm),
D = Absorbance value of standard, and
E = Weight of specimen in grams (gm).
4.4.2 Particle size. Particle size analysis shall be performed using the laser diffraction meth-
od outlined below. Particle size analysis and histogram are required with material certification.
1.
SAMPLE PREPARATION:
A. Weigh approximately 0.2 Grams (200 mg) of dye sample into a 30 mL beaker. Add 25
mL deionized water to the dye sample.
B. Add 1 or 2 drops of surfactant into the dye/water mixture.
C. Place an external ultrasonic probe (Sonics 130 watt) in the dye sample mixture. Soni-
cate the sample mixture for 2 minutes at 100% power setting.
2.
INTRODUCTION OF SAMPLE INTO THE INSTRUMENT AND TESTING:
A. After sonication is completed, place a clean stirring bar into the sample and move the
sonicated sample to a stirrer set to medium speed to keep all of the particles in the liquid in
suspension.
B. Set the laser diffraction particle size analyzer for MIE calculation with a Relative Re-
fractive Index at 1.50 --- .010.
C. Using a pipette transfer a 7.5 +/ --- 0.5 mL sample from from the beaker into the reser-
voir with the system circulating at a slow speed until proper particle loading is attained in the
instrument.
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