308 REPOET OX NITRIFICATION. 



gen is burnt in the air, or in oxygen, nitric acid is produced in small 

 quantity. 



The possibility of the formation of nitrates from the nitrogen 

 of the air being established, Longchamp argued that in many 

 cases of the occurrence of these bodies the supply of organic matters 

 was too small to account for the whole quantity. 



Facts^ that were known then, and some that have since been ob- 

 served, seem strongly to sustain Longchamp' s position, and have in- 

 clined many chemists to look upon his views as in the highest degree 

 probable, and as explaining a large part of the production of nitre ; 

 at the same time, however, not questioning the facts of the first-meu- 

 /ioned mode of nitrification. 



There is great difiiculty in demonstrating that in any given case of 

 nitrification the nitrogen cannot all come from ammonia, since am- 

 monia and ammonia-yielding substances reach the nitrifying soil, or 

 rock, in so many ways and from so many sources. They exist every- 

 where — on the surface of the earth, in all soils, and in many rocks; they 

 are diffused through the air and are washed down from it by rains, 

 and the water which percolates through the earth often carries large 

 quantities of them with it, so that, although it can be pointed out 

 that in certain cases the supply of them seems too small to account for 

 the whole production, yet it would be very hard to reduce this to 

 positive demonstration. 



While it has been long known that the nitrogen of the air will, un- 

 der certain circumstances, enter into the composition of a nitrate, it 

 has not until very recently been clearly shown by experiment that 

 this takes place under those particular circumstances under which 

 nitrification goes on in nature. 



In a paper read to the French Academy in November, 1855, M. 

 Cloez details experiments made by passing air, carefully freed from 

 organic matters and from ammonia, through porous substances of dif- 

 ferent kinds, (pounded bricks, broken earthenware, &c.,) impregnated 

 with potash and lime. After a certain time nitrates were found to 

 have been generated. These experiments attracted a good deal of 

 attention, and they have been repeated and some additional observa- 

 tions made. 



Though we have the fact of the production of nitrates from atmos- 

 pheric nitrogen clearly shown, we have still to settle the question as 

 to what is the modus operandi of the transformation — a point which is 

 not so simple as it might seem at first sight to be. While there are 

 several compounds of nitrogen and oxygen, none of them can be 

 formed by the direct union of these elements. They are derived in 

 one way or another from the decomposition of nitric acid or of the 

 nitrates; and in the case of the nitrates themselves, it does not appear 

 that they can be produced by the direct combination of nitrogen, 



« In 1775, a prize being offered by the French government for an essay on nitrification, 

 a large number of papers on the subject were received and referred to a commission of the 

 Academy. From these, and from the proceedings of the commission, Longchamp drew 

 most of "hi-i facts. The substance of them is found in " Les Memoires des Bavaus divers," 

 vol. xi. 



