Mercury
Mercury
Page 2 of 12
Mercury_PP_Other_CVM_Eng_Ody.fm
5. Add 7.5 g of
potassium permanganate
to the sample. Stir until
dissolved.
Alternatively, add a
10-gram measuring scoop
of potassium
permanganate to the
sample.
6. Cover the flask with a
watch glass. Begin
heating the sample to a
temperature of 90 °C after
the reagents have
dissolved. Do not boil.
Note: For a mercury standard
or reagent blank in distilled
water, the heat step is not
necessary.
7. Continue to stir and
heat the sample at 90 °C
for two hours.
The solution must remain
dark purple throughout
the entire digestion. Some
samples, such as sea
waters, industrial
effluents or other samples
high in organic matter or
chloride concentration,
require additional
permanganate. It may be
difficult to see a dark
purple color if the sample
contains black/brown
manganese dioxide
precipitate. Add more
potassium permanganate
if the solution is not dark
purple.
8. Cool the digested
sample to room
temperature.
A brown/black
precipitate of manganese
dioxide may settle during
cooling. If the digested
sample does not have a
purple color, the digestion
may be incomplete. Add
more potassium
permanganate. Return the
sample to the magnetic
stirring hot plate and
continue the digestion
until the purple color
persists.
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