Velp Scientifica
– UDK139 Operating Manual
10004762/B5
113
38 -
Method to separate ammonia in water from interfering
substances
Ammonia nitrogen is an important parameter for the management of a water
treatment plant.
Its direct determination in turbid waters, coloured or rich in magnesium, ammines and
other organic substances is subjected to large errors.
In these cases it
’s better to proceed with a separation of the ammonia by steam
distillation.
Procedure
1) Sample:
50 ml of water (or between 20 and 70 ml depending on ammonia
nitrogen content) accurately measured and introduced in the test tube.
2) Reagents:
the sample to be distilled must be alkalinized (indicator
phenolphthalein) with alkali or simply adding:
1,2 g magnesium oxide (MgO)
A saturated solution of magnesium oxide shows pH = 10,3.
3) Distillation e titration:
Set the following analytical parameters:
Addition of reagents:
H
2
O= 50ml.
H
3
BO
3
= 30ml (4% p/v)
NaOH= 0ml
Titrant: H
2
SO
4
0,01 N or H
2
SO
4
0,001 N
Distillation time= 4 min
Steam power= 100%
Press the button starting distillation cycle.
References
: ISO, norm n.o. 5664
300
