158 INDIRECT PRODUCTION OF AMMOxXIA- 



This opinion of Liebig, as well as the paramount influence he as- 

 cribes to ammonia over the vegetation of the globe, are based chiefly on 

 the fact that we know of no means by which ammonia can be formed 

 by the direct union of the hydrogen and nitrogen of which it consists. 



But the production of ammonia, by the indirect union of these ele- 

 ments, is daily going on in nature, and can even be effected by differ- 

 ent processes of art. Thus — 



1°. When organic substances, which contain no nitrogen, are oxidized 

 in the air, ammonia is not unfrequently f(jnned (Berzelius). Hence 

 it must be produced in unknown quantity during the annual decay of 

 all vegetable substances. 



2°. When organic substances are oxidized in the presence of air and 

 water — as when moist iron filings are exposed to the air (Chevallier), 

 or when certain oxidized substances are decom|)Osed in the air by 

 means of potassium (Faraday), or when metals, such as tin filings, are 

 rapidly oxidized by means of nitric acid, ammonia is also })roduced in 

 variable quantity. Hence the absorption of oxygen, even by the inor- 

 ganic substances of the soil, may give rise to the formation of ammonia. 

 But, 



3°. The fact which most clearly illustrates the production of am- 

 monia in nature, both on the surface of the earth, in t.he soil, and far in 

 the interior near the seat of volcanic fires, is this, that if a currant of 

 moist air be made to pass over red-hot charcoal, carbonic acid and am- 

 monia are simultaneously formed.* This is in reality only a repetition 

 in another form of what takes place, as above stated, when vegetable 

 matter decays, or iron filings rust in moist air. The carbon and the iron 

 decompose the watery vapour in the air, and coinbine with its oxygen, 

 while, ar the instantf of its liberation, the h^'drogen of the water com- 

 bines with the nhrogen of the air, and forms ammonia. 



The source of the ammonia evolved in volcanic districts, therefore, is 

 no longer obscure. The existence of combustible matter in such dis- 

 tricts, and at great depths beneath the surface, can in few cases be 

 doubted, and the passage of a mixed atmdsphere of common air and 

 steam over such combustible matter, at a high tem{)erature, appears to 

 be alone necessary to the production of ammonia. It is unnecessary, 

 then, to have recourse to doubtful speculations in order to account for 

 the natural reproduction of ammonia, to a certain extent, in the place 



* This experiment is easily performed by dratcing a. current of mixed atmospheric air 

 and steam throuj^h a red-hot gun-barrel filled with well-burned charcoal, and causing the 

 current, on leaving the barrel, to piss through water acidulated with muriatic acid. After 

 a time, the water, on evaporation, will be found to contain traces of sal-ammoniac. What 

 Hi us takes place in a small experiment of tliis kind must more readily and more largely 

 take place in the interior of the earth, where conibu.stible substances at a high temperature 

 happen to be exposed to a current of atmosplieric air, mixed with watery vapour. 



t A beautiful illustration of the tpndcncy which elementary substances have to unite with 

 each other at the instant of their liberation in wliat chemists call their nascent state, is men- 

 tioned by Runge. — Einlcitung in die technische Chemie, p. 373. 



If 1 p irt of hydrate of potash and 20 of iron filings be heated together, hydrogen only is . 

 given off. 



If I ot nitrate of potash and 20 of iron filings be heated together, nitrogen only is given off. 



But if 40 of iron filings be mixed with 1 of hydrate and 1 of nitrate of potash, and Uien 

 healed, ammotiia becomes perceptible. 



The nitrogen and hydrogen being given off together, at the same instant, some portions 

 of each find Lhiemselves in a condition to unite, and thus ammonia is produced. The same 

 result must follow in many natural operations, when hydrogen and nitrogen are set free 

 from a previous state of combination, al the same time, and in thc> presence of cue another. 



