The ammonia gas may also be decomposed by passing through a red hot
tube, and the presence of heated iron causes a slight degree of
decomposition. This sal-ammoniac is powdered and mixed with moist
slaked lime and then gently heated in a flask, when a large quantity
of gaseous ammonia is disengaged. The gas must be collected over
mercury or by displacement. The gas thus produced has a strong,
pungent odor, as can easily be determined by any one working around
the ammonia ice or refrigerating machines, for as our friend, Otto
Luhr, says, "It is the worst stuff I ever smelled in my life." The gas
is highly alkaline and combines readily with acids, completely
neutralizing them, and the aqua ammonia is one of the best substances
to put on a place burned by sulphuric acid, as has been learned by
those working with that substance, for although aqua ammonia of full
strength is highly corrosive and of itself will blister the flesh, yet
when used to neutralize the effect of a burn from sulphuric acid its
great affinity for the acid prevents it from injuring the skin under
such conditions.
The distilled gas, such as has just been described, is the anhydrous
ammonia used in the compressor system of refrigeration, while it is
the aqua ammonia that is used in the absorption system of
refrigeration.
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