Hydrazine

Hydrazine is a colorless fuming liquid, N2H4, derived from diazoacetic acid: used as a reducing agent in organic synthesis and as a fuel in jet engines.
Used in boiler feed water treatment, to reduce oxygen in the system, the normal level of hydrazine reserve to be maintained in the water is between 0.1 and 0.3 ppm. The chemical reaction with oxygen can be expressed as: N2H4 + O2 ==> 2H2O + N2

Excess hydrazine, in a boiler, breaks down to produce ammonia that has beneficial effects in raising the pH of the steam/condensate system and thus affords some protection to the system by neutralizing any carbon dioxide.
The reaction can occur in two ways:
3N2H4 ==> 4NH3 + N2
2N2H4 ==> 2NH3 + N2 + H2

Hydrazine should be handled with care since it is allergenic and carcinogenic to humans.