MIL-E-82756(OS)
methylene chloride portion in a 250-mL beaker and save for the EC determination (4.6.2.5).
Place the sodium carbonate extract in a 250-mL volumetric flask, and dilute it to the mark
with distilled water. Dilute a 15-mL aliquot of this solution to 100 mL with distilled water.
g.
Prepare a reference solution by diluting 100 mL of the 5 percent sodium carbonate solution
to 250 mL with distilled water and then further diluting a 15-mL aliquot of this to 100 mL
with distilled water.
h.
Determine the absorbance of the sample at 288 · as previously described in step d. Refer to
the standard curve (step e) to obtain the concentration.
i.
Calculate percent resorcinol as follows:
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where:
H = Concentration (mg resorcinol per 100 mL solution)
A = Weight of sample in grams
4.6.2.5 EC. Determine the EC content as follows:
a.
Evaporate the methylene chloride layer from the resorcinol extraction (4.6.2.4) to dryness.
b.
Transfer the residue to a 250-mL flask (equipped with a stopper) using 50 mL of glacial
acetic acid.
c.
Add, by pipette, 25 mL of potassium bromate-bromide solution which has been prepared as
follows:
(1) Add 5.6 grams of potassium bromate, which has been dried at 100·C for 2 hours, to a
beaker.
(2) Add 30 grams of potassium bromide.
(3) Add about 300 mL of distilled water to the beaker to dissolve the content, and dilute
the solution to 1 liter.
d.
Wet the stopper of the flask with a drop of 15 percent potassium iodide solution which has
been prepared by adding 15 grams of potassium iodide to 85 mL of distilled water.
e.
Add 5 mL of concentrated hydrochloric acid to the flask. Stopper the flask, swirl the
contents, and allow bromination to proceed for 1 minute.
f.
Immediately add 10 mL of 15 percent potassium iodide solution. Swirl the contents of the
flask.
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