306 REPORT ON NITRIFICATION. 



cumstances, it is natural that sometliing should have been known 

 about the manner of their formation from a very early period in the 

 history of" modern science. We find, accordingly, that as far back as 

 the 17th century it was held that the origin of nitre was due to the 

 decomposition of organic matters, both animal and vegetable. That 

 nitrates have, in large part at least, such an origin has long been 

 well established, and it has been the opinion of many that, when- 

 ever nitrates are formed, organic matters must be looked to as their 

 source. The way in which such matters come to be the source of 

 nitrates has been partially elucidated by modern investigations. 



Organic bodies as they are found in nature contain nitrogen in 

 greater or less quantity, and in decomposing they give it off in the 

 form of ammonia,* which is known to be convertible by the joint 

 action of oxidizing agents and of mineral bases, such as lime, potash, 

 (fee, into nitrates of those bases. It is shown by different examples, 

 and by general chemical analogy, that this conversion is greatly facil- 

 itated by the presence of solid substances in a finely divided or porous 

 condition, and we may assume that nitrates are formed from the am- 

 monia given off from decomposing matters by the action on it of at- 

 mospheric oxygen, and of porous bodies containing lime, potash, and 

 other mineral bases, t Experiments directly to this point are, those of 

 the French Academy, by which it Avas found that chalk, hung up in 

 a basket over decomposing blood, was partly converted into nitrate 

 of lime ;| and those of Dumas, who formed nitrates by passing ammo- 

 nia, mixed with moist air at a temperature of 212° Fah., over pieces 

 of chalk moistened with a solution of potash. § Kuhlmann, who has 

 made very important contributions to our knowledge of the subject, 

 converted the compounds of ammonia into nitrates by means of 

 various oxidizing agents. || 



This last-named chemist also performed the converse experiment 

 of producing ammonia from nitrates by the action on them of nascent 

 hydrogen and of such reducing or deoxidizing agents as furnish hy- 

 drogen. Upon these experiments, and upon other facts, he based 

 conclusions of considerable importance to agricultural chemistry. He 

 sets forth that when nitrates are mixed with an ordinary soil at that 

 depth below the surface at which they are out of contact of air, they 

 are reduced to ammonia b}^ the agency of the organic matter present; 

 and that conversely, when the ammonia in the soil rising to the sur- 

 face comes into contact with the air, it is converted into nitrates of 

 lime, potash, and whatever other bases may be contained in that par- 

 ticular earth. The reduction of the nitrate to ammonia in the deeper 



■'■'The chemical formula of ammonia is NHg. It is evolved in the gaseous form, in 

 combination with certain volatile acids, also the products of organic decomposition, chiefly 

 with carbonic and hydrosulphuric acids. 



t Good examples of such bodies are found in ordinary earth ; and a mode of producing 

 nitrates, long practicinl and well known, consists in mixing earth with organic raatters,and 

 allowing decomposition to go on with exposure to the air. 



J Memoires des Savans Divers, vol. xi. 



^Comics Rendus, December, 1846. 



II Cornier Rendus, November, IS-iG. 



