212 



CHEMISTRY. 



itself with the theory following, of Nitrifica- 

 tion ; while it would further appear also, that 

 many of the reactions ascribed to ozone may 

 be regarded as due to formation of nitrous acid 

 during decomposition of atmospheric nitrogen 

 (NN) in presence of water and nascent oxygen. 



IV. NITRIFICATION. The subject of the for- 

 mation of the nitre-beds, or vast collections of 

 nitrates in the soil of certain hot countries, or 

 in caves, always one of great practical interest, 

 appears very recently to have received a new 

 elucidation through researches in theoretical 

 chemistry. The most important natural source 

 of nitre is the nitriferous soil of certain districts 

 in Hindostan, yielding chiefly nitrates of potash 

 and lime. Similar but less productive beds are 

 found in parts of Persia, Egypt, Hungary, Spain, 

 and South America. The floor of many caves 

 is found largely impregnated with nitrates ; in 

 this respect the Mammoth Cave of Kentucky 

 was the most noted, until in 1812 it was indus- 

 triously worked for nitre. In the desert of 

 Atacama, S. A., immense beds of nitrate of 

 soda exist; and another at Iquique (Peru), 

 quite inexhaustible in extent, is now largely 

 worked. (For an account of the last named, 

 see " Jour, of Franklin Inst.," June, 1862.) 



The " Smithsonian Report," 1861, contains an 

 able " Report on Nitrification," by Dr. B. F. 

 Craig, in which the subject is considered under 

 the following heads : 1. Our knowledge of the 

 laws which govern the formation of nitre. 2. 

 The manner and extent of its production in na- 

 ture. 3. The methods that have been practised 

 for its artificial formation. 4. The methods of 

 artificial formation that have been suggested, 

 or those which the present state of our knowl- 

 edge would suggest. 5. Experimental investi- 

 gations it would be desirable to make, for the 

 advancement of the theory and practice of the 

 manufacture of nitre. 



A theory dating as early as the 17th century 

 referred the formation of the nitre-beds to col- 

 lection and decomposition of organic matters, 

 vegetable and animal ; but as this scarcely suf- 

 ficed for the magnitude of the product, various 

 attempts have been made to show how nitric 

 acid could be generated from constituents of 

 the air. This doctrine was first distinctly ad- 

 vanced, as well as supported by experiments, 

 by Longchamp, in a paper before the French 

 Academy, 1823. Before the same body, Nov. 

 1855, M. Cloez detailed experiments made by 

 passing air, carefully freed from organic matters 

 and ammonia, through porous substances of 

 different kinds (pounded bricks or earthenware, 

 &c.), impregnated with potash and lime; the 

 result being that nitrates of these bases were 

 formed. In this case, the action is like that 

 of spongy platinum on hydrogen and oxygen 

 gases, the mechanical condensation of the gases 

 within fine pores or on certain surfaces result- 

 ing like compression in evolution of heat and 

 chemical union ; and such an action could be 

 supposed to go on also in a porous soil laved by 

 the atmosphere. Thus finally the fact that ni- 



trates, or rather the nitric acid in them, is pro- 

 duced from the atmosphere is settled : the 

 question of the mode remained. Dr. Craig fa- 

 vors the theory proposed by Dr. G. C. Schceffer, 

 based upon a general tendency of certain com- 

 pounds in this case, as he supposes, preformed 

 nitrous oxide (NO), to assume the elements of 

 water, giving rise to nitrate of ammonia, and 

 by substitution of potash, &c., to the fixed ni- 

 trates. Dr. H. B. Jones (" Philos. Transactions," 

 1851) had described the cases of direct union 

 of the atmospheric nitrogen and oxygen, in in- 

 stances of combustion taking place in the air. 

 What Schonbein has now done is, to determine 

 the fact and the conditions of a new source of 

 nitrous, and probably therefore of nitric acid, 

 and thus to offer a substantially new theory of 

 the precise mode of nitrification. 



Let a piece of clean linen, drenched with 

 distilled water, dry in the open air (the water, 

 of course, gradually evaporating from it) ; then 

 moisten it again with pure water, wring out 

 this liquid, and acidulate it with pure dilute 

 sulphuric acid ; it will strike a blue with starch 

 paste containing iodide of potassium the most 

 delicate test for the nitrites. Moisten a bit of 

 filtering paper with a dilute solution of chemi- 

 cally pure potash, and suspend it for 24 hours 

 in the air : examination will then show it to 

 contain a perceptible quantity of nitrite ; and 

 by longer exposure this is increased. Or, better 

 still, heat in a clean porcelain basin pure water 

 to about 133 F., and over the evaporating sur- 

 face suspend bands of filtering paper soaked in 

 a weak solution of potash or soda, or their car- 

 bonates ; in a very short time enough of the 

 nitrite of either alkali will have accumulated 

 to produce the reaction of such salt. In vari- 

 ous other ways, involving evaporation of water 

 in air, the same results are obtained ; where no 

 base is supplied, the nitrite of ammonia being 

 the product found. The conclusion reached is 

 that, universally, where water is evaporating 

 in contact with atmospheric air, a nitrite of 

 ammonia, or of such other alkaline base as may 

 be present, is formed. Of course, all linen and 

 other fabrics dried in the air must contain dis- 

 coverable quantities of nitrite of ammonia due 

 to this source ; and as a fact the purest water 

 suffered to -evaporate spontaneously into the 

 air, took up enough of this salt forming at its 

 surface to produce the nitrite reaction. Thus, 

 the fact before known that the purest water 

 slightly charged with sulphuric acid or potash, 

 kept evaporating at near 133 F., in the open 

 air, and replenished, comes to show first a per- 

 ceptible quantity of ammonia, and afterward of 

 nitrous acid, is now explained. The formation 

 of nitrite of ammonia about slowly burning 

 phosphorus, detected some months before, 

 Schonbein now refers to the effect of evapora- 

 tion of water going on about the heated phos- 

 phorus. If, in these cases, the composition of 

 nitrite of ammonia be regarded as (NH 4 .NO 4 ), 

 it will be seen to be formed by direct union of 

 4 atoms of evaporating water with 2 atoms of 



