MIL --- DTL --- 3277F(EA)
4.4 Tests.
4.4.1 Purity. Prepare and measure the absorbance of a standard Solvent Green 3 solution
and a methylene chloride (dichloromethane) solution of the specimen in the following con-
centrations: 2, 4, 6, and 8 micrograms dye per milliliter methylene chloride (mg/mL). Using a
spectrophotometer, measure the absorbance of the solutions at 642 +/ --- 3 nanometers (nm)
using methylene chloride as the reference liquid in the spectrophotometer. Calculate the per-
cent by weight purity for each dilution as follows:
Percent purity = (ABC)∕(DE)
where: A = Percent purity of the standard,
B = Absorbance value of the specimen,
C = Weight of standard in milligrams (mg),
D = Absorbance value of standard, and
E = Weight of specimen in milligrams (mg).
Report the percent purity as the average of the four calculated values.
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.
D. Run the sample immediately. Report the mean particle size as well as the percentage
below 10 microns for the sample.
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