Velp Scientifica
– UDK139 Operating Manual
10004762/B5
120
42 - Determination of ammonia nitrogen in organic fertilizers
according to the Kjeldahl method
Procedure
1) Sample:
the sample must be ground in order to obtain an homogeneous powder
(particles dimension 1mm). 0.7-3.5g of sample are then accurately weighed (with a
precision of 0.1 mg) and quantitatively transferred in a test tube.
2) Distillation and titration:
the sample to be distilled must be alkalized
(phenolpthalein indicator) by adding 2g or a higher quantity of Magnesium oxide
(MgO) free from carbonates. Place the test tube containing the alkalized sample in
the UDK 139 unit.
Select the following analytical parameters:
Factor: 0.00
Addition of reagents:
H
2
O: 50 ml
H
3
BO
3
: 30 ml
NaOH: 0 ml.
Titrant: HCl 0.2N
Push START to start the analysis.
References:
AOAC, Official Methods of Analysis, method 920.03.
307
