160 FORMATION OF NITRIC ACID. 



Of these nitrates, as they do of ammonia, the rivers niiisl be continu- 

 ally bearing a portion to the sea, but there are in nature unceasing pro- 

 cesses of reproduction, by which not only this waste of the nitrates is 

 repaired, but that further waste, also, which is caused by their absorp- 

 tion into the roots and subsequent decomposition in the interior of })lants. 

 Let us siiortly consider these processes of reproduction. 



1°. When a succession of electric sparks is passed through common 

 air, nitric acid (NO 5) is slowly but sensibly formed. The currents of 

 electricity which in nature traverse the atmosphere must produce the 

 same effect, and the passage of each flash of lightning through the air 

 must be attended by the formation of some portion of this acid. 



After a thunder-storm plants appear wonderfully refreshed ; in thun- 

 dery weather they grow most luxuriantly, and other things being equal, 

 those seasons in which there is much thunder are observed to be the 

 most fruitful. Some have ascribed these results to the immediate agency 

 of electricity on the growth of plants. — [Sprengel, Chemie, I., p. 99.] 

 It is not equally possible that they maybe connected with this necessary 

 production of nitric acid ? 



Iri the rain which fell during 17 thunder-storms, Liebig found nitric 

 acid always present and generally in combination with lime and am- 

 monia. In the rain which fell on 60 other occasions, he could detect it 

 only twice. In minute quantity nitric acid is difficult to detect. How 

 much then must be formed in a thunder-storm, even in our climate, to 

 make the presence of this acid always appreciable in the rain that falls 

 — how vast a quantity in those warmer climates where such storms are 

 so frequent and so appalling! 



2°. When a mixture of ammonia with oxygon gas is exploded by 

 passing an electric spark through it, a quantity of nitric acid is formed, 

 even when the oxygen is not sufficient to oxidize the whole of the am- 

 monia* (Biscliof). Hence, if in the air, as we have seen reason to be- 

 lieve, the ammonia given off' from decaying animal matters, and from 

 other sources, be decomposed by the atmospheric electricity, — there will 

 necessarily be formed at the same instant a portion of nitric acid, at the 

 expense of the nitrogen of the ammonia itself. This nitric acid will, as 

 necessarily, combine with some of the ammonia which still remains in 

 the air. Hence the existence and production of nitrate ojf ainmonia in 

 the atmosphere, and the consequent presence of this acid along with am- 

 monia in rain water. 



Thus the very cause which in the preceding section was shown to 

 operate in constantly diminishing the amount of ammonia in the air, 

 and the operation of which certainly renders improbable the existence 

 of this compound in the atmosphere in the large quantity supposed by 

 some [see especially Liebig's Organic Chernistry applied to Agriculture, 

 p. 74], this same cause is at the same moment constantly reproducing 

 nitric acid. And, though much of what is thus produced must neces- 

 sarily, as in the case of ammonia, je carried down to the sea by the 

 rains, or be directly absorbed by the waters of the ocean themselves, yet 



* It was shown above (p. 157), that I of ammonia ( NHj ) requires 3 of oxygen to decom- 

 pose it, forming 3 of water, and setting: the nitroj^en free. But, in reality, as Bischof has 

 eliown, the nitrogen is nut wholly set free, but a portion both of its hydrogen and nitrogen 

 combine with oxygen (are oxidized) at the same instant, forming simultaneously both water 

 (HO), and nitric acid ( NO5 ). 



