NH3 a colourless pungent-smelling gas about 
two-thirds as dense as air. It is used mainly 
to produce nitrogenous fertilizers. Ammonia 
is produced by the Haber and cyanamide 
processes. It is soluble in water, forming 
ammonium hydroxide, NH4OH. The solution is 
strongly alkaline, and forms crystalline 
salts on neutralization with acids. In 
aquatic organisms and some insects, 
nitrogenous waste (from breakdown of amino
acids and so on) is excreted in the form of
ammonia, rather than urea as in mammals.