_Prop._ Gaseous, colourless, invisible; highly pungent, acrid, irritating and alkaline; irrespirable, unless very largely diluted with air; extinguishes combustion; burns slowly in oxygen; sp. gr. 0·589; 100 cub. inches weigh 18·26 gr. Under a pressure of 6·5 atmospheres, at 50° Fahr., it forms a transparent, colourless liquid of the sp. gr. 0·731; at 60° Fahr. this liquid expanded into 1009 times its volume of ammoniacal gas; at -40° Fahr., and the ordinary atmospheric pressure, it forms a subtle colourless liquid, which at -103° Fahr. freezes into a white, translucent, crystalline substance. (Faraday.) It is highly basic; all its salts are either volatilised or decomposed at, or under, a red heat——those with a volatile acid sublime unchanged——those with a fixed acid lose their ammonia. It is decomposed into its elements by transmission through a red-hot tube; and when in contact with metallic oxides or spongy platinum, at the same temperature, the newly evolved hydrogen unites with the oxygen of the oxide or of the atmosphere, forming water. Water at 50° Fahr. absorbs 670 times its volume of this gas, and the solution has the sp. gr. 0·875. Its concentrated aqueous solution boils at 130°, and freezes at -40° Fahr. _Tests, &c._ Ammonia is recognised by——1. Its pungent odour:——2. By turning vegetable blues green, and vegetable yellows brown; but which soon regain their previous colours, especially on the application of heat:——3. By producing dense white fumes when brought in contact with those of hydrochloric acid:——4. By the Nessler test (see WATER, QUANTITATIVE AND QUALITATIVE ANALYSIS OF):——5. If a saturated solution of arsenious acid is mixed with a solution of nitrate of silver (strength 2%) a trace of ammonia causes the formation of try-argentic arsenite:——6. Böttger says a very delicate test for ammonia is afforded by an aqueous solution of carbolic acid. On adding to a liquid containing the smallest quantity of ammonia, or an ammoniacal salt, a few drops of this solution, and then a small quantity of a filtered solution of chloride of lime, the liquid becomes green, especially when warmed. _Phys. eff., &c._ Inhaled, undiluted with air, it is an irritant poison, producing spasms of the glottis, convulsions, and death; even when diluted it acts as a powerful acrid, and local irritant; applied to the skin it causes vesication. The use of the pungent odour of common ‘smelling salts,’ in syncope, headache, &c., is well known. Largely diluted with air, it has been recently highly extolled in chronic hoarseness, asthma, &c.; and as an antidote to the fumes of bromine, chlorine, and hydrocyanic acid. (Smee.) _Ant., &c._ The vapour of acetic acid or common vinegar, freely inhaled. It may be produced by sprinkling a little on a piece of hot iron, as a heated shovel. If bronchial inflammation follows, it must be treated by purgatives and a low diet; and, if severe, and the patient be plethoric or robust, by venesection or cupping.