am·mo·ni·ac Am·mo·ni·a·cal a. Of, pertaining, or containing ammonia, or possessing its properties; as, an ammoniac salt; ammoniacal gas.
 Ammoniacal engine, an engine in which the vapor of ammonia is used as the motive force.
 Sal ammoniac [L. sal ammoniacus], the salt usually called chloride of ammonium, and formerly muriate of ammonia.

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