Hach DR/700 - Page 56

1-38
Water
Sample
Volume
(mL)
=
50
% solids
GENERAL DIGESDAHL DIGESTION
1. Transfer a
preweighed or a
premeasured amount
of sample into a
100-mL volumetric
flask; see Table 8.
The amount
transferred should not
contain more than 0.5
g of solids or organic
liquids. The
maximum volume for
water samples is 50
mL. In samples with
more than 1% solids
present, use the
formula below:
Example: If solids are
10% of total volume of
sample, the maximum
volume of liquid sample
would be 5 mL.
Note: Several 50-mL
sample aliquots of the
sample may be digested
in succession to
concentrate a sample.
Note: If liquid is too
viscous to measure,
preweigh the sample
into the digestion flask.
2. Add concentrated
sulfuric acid according
to Table 8 to the
volumetric flask and
two or more silicon
carbide (Carborundum)
boiling chips for liquid
samples.
Note: Boiling chips can
be pretreated by soaking
in 1:1 nitric acid and
rinsing thoroughly with
deionized water.
Treatment may be
particularly important
in low level work.
Silicon carbide boiling
chips are recommended.
Note: Use only Hach
digestion flasks.
Volumetric flasks with
concave bottom should
not be used.
Warning
A safety shield placed
between the operator
and the Digesdahl is
required. Safety glassed
are mandatory.
Caution
Experimentation with
the Digesdahl Apparatus
is not recommended. See
Safety Considerations
following these steps.
3. Turn on the water
to the aspirator and
make sure there is
suction to the
fractionating column.
Turn the temperature
dial to a heat setting of
440 °C (825 °F). For
meat digestion, set to
468 °C (875 °F).
Note: Wait for the
proper temperature to
be reached before
sample is placed on the
heater.
Note
Specific method
manuals for a variety of
sample types are
available, free of charge
from Hach Company.
See Application -
Specific Manuals
following these steps for
a complete listing. New
methods are continually
being developed. Please
contact Hach Company
World Headquarters,
(303) 669-3050, for a
current listing.