4
A. THEORY OF OPERATION
What is ammonia?
Ammonia (NH
3
) is a poisonous and pungent-smelling colorless gas that makes the eyes water. Ammonia is readily
soluble in water. The aqueous solution has an alkaline reaction and is known as ammonia water or tincture of
ammonia. In conjunction with acid, ammonia forms salts that disassociate in water, to form ammonium ions (NH
4+
)
and the corresponding anions. In nature, ammonia is produced by the decomposition of animal or vegetable
material that contains nitrogen.
Typical areas of application for ammonia sensors
The ProMinent ammonia analyzer sensor can be used to measure ammonia (NH
3
) in aqueous solutions. Ammonia in
an aqueous solution is in a pH-dependent equilibrium with ammonium ions. If ammonium ions are converted into
ammonia by the addition of an alkali, then the sensor will detect the resulting ammonia gas. The ammonium ions
themselves will not be detected.
Fig. 1: ProMinent Ammonia Analyzer