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|  MIL-C-70501 (AR)
Conduct digestion over a safety-approved heating device adjusted
to bring 250 ml.
minutes.
DISTILLATION - Use a Kjeldhal flask of 500 to 800 ml.
capacity fitted with a rubber stopper. The low end of an
efficient scrubber bulb or trap is passed through the rubber
stopper to prevent mechanical carryover of NaOH during
distillation.
Use rubber tubing to connect the upper end of
the bulb to the condenser tube. Trap the condenser outlet to
in the receiver.
Analysis
Quantitatively transfer the residue from 4.5.1.3.3 to a Kjeldahl
flask, add 3-4 Hengar granules, 0-7g. of HgO, 15.0g. of
Place the flask in an inclined position, and heat gently until
Boil the contents of the flask briskly until
frothing ceases.
Continue boiling for 1/2 hours minimum.
the solution clears.
Allow the solution to cool to room temperature. Add 200 ml.
Cool the solution to below
Add 25 ml. thiosul-
fate solution and mix to precipitate the mercury. Tilt the
flask and add a layer of 100 ml. NaOH solution without agita-
tion.
Immediately connect the flask to the distilling bulb on
the condenser. With the tip of the condenser immersed in the
boric acid in the receiver, rotate the flask to mix the contents
thoroughly.
Heat the flask until all of the
distilled, (approximately 250 ml.) Titrate the boric acid
solution with the standard acid using a mixed indicator contain-
ing 4 drops of methyl red, and 2 drops of methylene blue solu
tion.
Correct for the reagent blank. Calculate the percent
acrylic as follows:
Percent (%) Acrylic
Where:
V
=
Volume of standard acid for sample, ml.
B
=
Volume of standard acid for blank, ml.
N
=
Normality of standard acid
W
=
Dried sample weight, g.
4.5.1.3.5 Resin and additives, kraft and polyester staple
fiber.
Calculate the percent resin and additives, kraft and
polyester staple fiber as follows:
18
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