Aqua ammonia or liquor ammonia is formed by dissolving
the ammonia gas in water. One volume of water will dissolve seven
hundred times its bulk of this gas, and is then known as aqua ammonia,
in contradistinction to anhydrous ammonia, the latter designating term
meaning without water, while the term aqua is the Latin word for
water.
Anhydrous ammonia, the gas, may be reduced to the liquid form at
ordinary temperatures when submitted to a pressure of about 95 pounds.
During the process of liquefaction the ammonia gives up a large amount
of heat, which if absorbed or radiated while the ammonia is in the
liquid condition, the gas when allowed to expand will absorb from its
surroundings an amount of heat equal to that radiated, producing a
very great lowering of temperature. It is this principle that is
utilized in refrigeration and ice making. In the absorption system,
where aqua ammonia is used, the liquor is contained in a retort to
which heat is applied by means of a steam coil, and a great part of
the gas which was held in solution by the water is expelled, and
carries with it a small amount of water or vapor. This passes into a
separator in the top of a condenser, from which the water returns
again to the retort, the ammonia gas, under considerable pressure,
passing into the coolers.
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