Agriculture Reference
In-Depth Information
Soil Sample
Subsample
Subsample
Subsample
Steam Distill
Digest
Sulfuric Acid
Catalyst
Oxidation
Nitrite to Nitrate
Reduction to
Ammonia
Steam Distill
Steam Distill
Inorganic
Ammonia
Inorganic
Ammonia and
Ammonia
from Organic
Matter
Inorganic
Ammonia and
Ammonia from
Nitrite and
Nitrate
Figure 6.7.
Flow diagram for determination of ammonia, organic nitrogen, nitrite, and nitrate
using kjeldahl apparati [6].
6.5.
KJELDAHL—ORGANIC NITROGEN
Caution
:
Extreme caution must be exercised in carrying out a kjel-
dahl procedure. Digestion involves the use of concentrated sulfuric
acid and in the past selenium and mercury have both been used a cat-
alyst. Older equipment may be contaminated with these elements and
should be treated with caution. During the digestion process copious
amounts of
choking, corrosive, and toxic
sulfur dioxide fumes are
released. These fumes must be removed by evacuating them using an
aspirator or some other appropriate method. Standard kjeldahl
equipment will come with components and directions for removing
SO
2
safely. Ammonia distillation involves use of highly concentrated
caustic sodium hydroxide solutions, which must be handled with care.
Sodium or potassium hydroxide spilled on skin is best removed with
a dilute solution (1-2%) of acetic acid in water followed by washing
with soap and water.
