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data sheets, product labels or otherwise, is unfortunately not always as an easy task for the potential
user. In this matter, particular attention must be paid to the methods used by various manufacturers
for the determination and reporting of the amount of SRN, and CRN present.
The SRN in most commercial liquid SRN-containing fertilizers presently manufacture in the United
States, Canada, and Europe is comprised of the water-soluble reaction products of urea with
formaldehyde, or from the reaction products of urea, formaldehyde and ammonia.
In the reaction of urea and formaldehyde, based on the nature of the catalysts, whether an acid
catalyzed reaction, or a based catalyzed reaction, different urea-formaldehyde adducts (ureaforms) will
form and the resulting product will be either liquid or solid
4
.
Urea
NH
2
H
2
N
O
H H
O
NH
H
2
N
O
CH
2
OH
NH
HN
O
CH
2
OH
CH
2
OH
Base
MMU
a
DMU
b
+
+
a
monomethylourea;
b
dimethylolurea;
c
methylenediurea;
d
dimethylenetriurea
Reaction of urea and formaldehyde is not 100% and some unreacted urea will remain in the final
product. If the reaction product is a solid, the amount of unreacted and free urea could be determined
by AOAC Official Method 945.01 (Water-Soluble Nitrogen), and AOAC Official Method 955.05 (Nitrogen
Activity Index). Determination of water-insoluble nitrogen in mixed fertilizers has been studied by Katz,
et.al.
5,6
NH
2
H
2
N
O
NH
H
2
N
O
H H
O
NH
H
2
N
O
NH
2
HN
O
CH
2
NH
HN
O
NH
2
HN
O
CH
2
CH
2
MDU
c
DMTU
d
+
Acid
+