A combination of 1 Eq. of Nitrogen and 3 of Hydrogen. At ordinary temperatures it is gaseous. By a pressure of 6.5 atmospheres, at 40° F., it is condensed into a transparent, colourless fluid. Sp. gr. 0.76. Dry Ammonia has no alkaline reaction, the presence of water is required for the manifestation of this property. By assuming the existence of the hypothetical metal Ammonium, NH4, the chemical nomenclature of the Salts of Ammonia is assimilated to that of the Salts of the other alkaline metals. This nomenclature has been adopted by the compilers of the British Pharmacopoeia.

Phys. Effects of Ammonia and its Salts. Hufeland* observes that the officinal, and probably all, the salts of Ammonia have the property, to a greater or less degree, of dissolving the blood corpuscles, although slowly, and the protein textures generally. When blood is combined with an ammoniacal salt, it acquires, generally, a brighter red; but this soon passes into a brownish red hue: it does not coagulate, but forms, at best, a loose, semi-fluid cruor, the corpuscles begin to disappear, and the whole becomes more limpid. Blood thus decomposed, progressively evolves distinct traces of Ammonia. It is very probable that we may partially explain, upon chemical grounds (solution, and disengagement of Ammonia), why large doses of the Hydrochlorate of Ammonia act as poisons, and smaller doses, long continued, induce a scorbutic condition. Yet the same salt, judiciously exhibited, furnishes a valuable stimulant to the secretory and excretory apparatus. That chemical attraction is inadequate to account for the therapeutic and poisonous quality of the hydrochlorate is obvious, inasmuch as it exercises a general action and induces inflammation of the stomach, even when introduced into the subcutaneous cellular tissue.

Dr. B. W. Richardsont has come to the conclusion that the coagulation of the blood depends on the evolution from it of Ammonia. Without going into the question of the correctness of this view, which has met with strenuous opposition both here and on the Continent, it is of importance to notice his observations on the physiological effects of Ammonia. He has confirmed the statement that the effect of the addition of Ammonia to freshly drawn blood, is to prevent coagulation, and to destroy and alter the blood globules. In this respect the action of Ammonia resembles that of the fixed alkalies. When Ammonia or its carbonate are administered for some time to animals or man, the effect is to modify the blood corpuscles; they become easily soluble, cre-nate at the edge, many-sided, colourless, transparent, collapsed, and loosely agglomerated, but not in rolls; and the blood when drawn, or after death, is absolutely fluid or loosely coagulated. These changes in the blood he thinks correspond closely with those observed by Jenner in the blood of patients suffering from typhous fevers. By making animals breathe or swallow Ammonia, Dr. Richardson has been able to induce a condition resembling the typhoid in man. A superalkaline condition of the blood from the presence of an excess of Ammonia is observed in yellow and typhous fevers, and other diseases of the typhoid type, and in cases where the function of the kidney is suppressed. In such conditions, therefore, he believes that the administration of Ammonia and other alkalies is contra-indicated. The ammoniacal condition of the blood is recognized by the ammoniacal condition of the breath, tested by a rod dipped in hydrochloric acid. Ammonia acts in the first instance as an excitant to the heart and respiration, but in its principal effects he believes it does not differ from the other alkalies. It is most useful in all cases where fluidity of the blood and plastic tissues are required - in all cases of the inflammatory type when fibrin is in excess, and where there is rapid oxidation - in cases of induration of the tissues; and it may be given as the other alkalies when acidity of the secretions is a prominent symptom, as in acute rheumatism.

* Chemie und Med. &c, Berlin, 1841.

Astley Cooper Prize Essay on the Coagulation of the Blood.

Salts of Ammonia with a vegetable acid, such as the acetate, citrate, or tartrate, exert no influences in producing an alkaline condition of the urine. The Ammonia is either oxidized and converted into nitric acid, or more probably eliminated by the skin and mucous membranes. It does not pass through the renal organs.*

The vapour of Ammonia is powerfully irritant; if inhaled, it produces spasm of the glottis, and death results from Asphyxia. The diluted vapour causes much irritation of the lining membrane of the bronchial tubes, and also that of the mouth and nose. It is also a powerful nervine stimulant, as is best seen in the application of the vapour in syncope. Ammonia is the basis of the following preparations: -