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Solid Samples
Liquid Samples
Table 2 Some Properties of Kjeldahl Nitrogen Standards (#22778-00)
Formula
Structure
Molecular Weight
Melting Point, °C
% Nitrogen
% Protein
Digestability Index
Moisture
Absorption
at 25 % RH
at 50% RH
at 90% RH
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1. Weigh 0.25 grams of a Primary Standard for Kjeldahl Nitrogen.
Digest the standard following the general digestion procedure.
2. Any of the three standards may be used. Ammonium p-toluenesulfonate
(185.5 mg/L TKN) is the least difficult to digest. Glycine
p-toluenesulfonate (141.63 mg/L TKN) is moderately difficult to digest,
and Nicotinic Acid p-toluenesulfonate (118.58 mg/L TKN) is the most
difficult to digest.
1. Weigh 10.000 grams of a Primary Standard for Kjeldahl Nitrogen.
2. Transfer to a 1-liter volumetric flask and dilute to the mark.
3. Using a volumetric pipet, add 15 mL of the prepared solution to the
digestion flask and digest the standard following the general
digestion procedure.
4. Any of the three standards may be used. Ammonium
p-toluenesulfonate (111.03 mg/L TKN) is the least difficult to digest.
Glycine p-toluenesulfonate (84.98 mg/L TKN) is moderately difficult
to digest, and Nicotinic Acid p-toluenesulfonate (71.15 mg/L TKN) is
the most difficult to digest.
A primary standard set, containing one bottle of each of the standards,
may be purchased from Hach Company. Table 2 lists some of the
properties of the three primary standards.
Ammonia PTSA
C
H
O
SN
7
11
3
189.235
—
7.402
46.261
0
0.04%
0.07%
0.14%
Glycine PTSA
C
H
O
SN
9
13
5
247.277
199
5.664
35.403
3
0.03%
0.047%
0.15%
26
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Nicotinic Acid PTSA
C
H
O
SN
13
13
5
295.316
179
4.743
29.643
10
0.00%
0.01%
0.08%
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