THE CHEMISTRY OF THE ANIMAL BODY. 955 



flame and animal life are extinguished, owing to lack of oxygen. It acts as 

 a diluent of atmospheric oxygen, thereby retarding combustion, but on higher 

 animal life it is certainly without direct influence. 



Ammonia, NH 3 , is found in the atmosphere as nitrate and nitrite to the 

 extent of one part in one million. It is found in the urine in small quantities, 

 is a constant product of the putrefaction of animal matter, and is a product of 

 trypsin proteolysis. 



Preparation. (1) Through the action of nascent hydrogen on nascent 

 nitrogen. This may be brought about by dissolving zinc in nitric acid, 



3Zn + 6HNO 3 = 3Zn(NO 3 ) 2 + 6H. 



10H + 2HNO 3 = 6H 2 O + 2N. 



N + 3H = NH 3 . 



Ammonia is produced in a similar way in the dry distillation of nitro- 

 genous organic substances in absence of oxygen, being therefore a by-product 

 in the manufacture of coal-gas. In putrefaction nascent hydrogen acts on 

 nascent nitrogen, producing ammonia, which in the presence of oxygen becomes 

 oxidized to nitrate and nitrite, or in the presence of carbonic oxide is con- 

 verted into ammonium carbonate. Ammonium nitrite is likewise formed on 

 burning a nitrogenous body in the air, in the evaporation of water, and on the 

 discharge of electricity in moist air, 



2N + 2H 2 O = NH 4 NO 2 . 



At the same time a small amount of nitrate is formed in the above three 

 processes, 



2N + 2H 2 O + O = NH 4 NO 3 . 



Hence these substances find their way into every water and soil, and furnish 

 nitrogen to the plant. The value of decaying organic matter as a fertilizer is 

 likewise obvious. 



Properties. Ammonia is a colorless gas of pungent odor. It readily dis- 

 solves in water and in acids, entering into chemical combination, the radical 

 NH 4 appearing to act like a metal with properties like the alkalies, and its 

 salts will be described with them. Very small amounts of ammonia instantly 

 kill a nerve, but upon muscular substance it acts first as a stimulant, provok- 

 ing contractions. 



Detection. On warming an ammonium salt with sodium hydrate, ammonia 

 is set free, recognizable by its smell, by the fact that it turns turmeric paper 

 brown, and that even in smallest traces it gives a yellow coloration, or, in 

 greater amounts, a reddish precipitate in Nessler's reagent (mercuric iodide dis- 

 solved in potassium iodide and potassium hydrate). 



AMMONIA IN THE BODY. If it be agreed with Hoppe-Seyler that normal 

 decomposition in the tissues is analogous to putrefaction, then nascent hydrogen 

 acting on nascent nitrogen in the cell produces ammonia, which in the presence 

 of carbonic acid becomes ammonium carbonate, and in turn may be converted 

 into urea by the liver. If acids (HC1) be fed to carnivora (dogs) the amount 



