45-37
PHENOLS, continued
necessary to elevate the flask with a laboratory jack. Place a stirring bar
into the distillation flask.
b) Measure 300 mL of sample in a 500-mL graduated cylinder. Pour it
into the distillation flask.
c) Using a serological pipet, add 1 mL of Methyl Orange Indicator
Solution to the distillation flask. Turn on the heater power switch. Set
the stir control to 5.
d) Add Phosphoric Acid Solution, 10%, drop-wise, until the indicator
changes from yellow to orange.
e) Add the contents of one Copper Sulfate Powder Pillow and allow to
dissolve. (Omit this step if copper sulfate was used to preserve the
sample.)
f) Turn on the water and adjust so a constant flow of water is maintained
through the condenser. Set the heat control setting to 10.
g) Turn off the still after collecting 275 mL of distillate.
h) Fill a 25-mL graduated cylinder to the 25-mL mark with
demineralized water. Turn the still back on. Add the water to the flask.
Resume heating until another 25 mL of distillate is collected.
i) Using a graduated cylinder, remeasure the distillate to be certain
300 mL has been collected. The distillate may now be analyzed for
phenol by the 4-aminoantipyrine method.
SUMMARY OF METHOD
The 4-aminoantipyrine method determines all ortho- and meta-
substituted phenols or napthols but not para-substituted phenols. These
phenols react with 4-aminoantipyrine in the presence of potassium
ferricyanide to form a colored antipyrine dye. This dye is then extracted
from aqueous solution with chloroform and the color is measured at
460 nm. Sensitivity of the method varies with the type of phenolic
compound. Because a water sample may contain various types of
phenolic compounds, the results of the test are expressed as the
equivalent concentration of phenol. Wastewater and seawater samples
may require pretreatment.
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