AND AIR 227 



many reactions with hydrogen itself and with many hydrocarbons ; 

 although these reactions cannot be effected by exposure to a red heat. 

 Thus, for instance, a series of electric sparks passed through a mixture 

 of nitrogen and hydrogen causes them to combine and/orm ammonia** 

 or nitrogen hydride, NH 3 , composed of one volume of nitrogen and 

 three volumes of hydrogen. This combination is limited to the forma- 

 tion of 6 per cent, of ammonia, because ammonia is decomposed, 

 although not entirely (f^o) by electric sparks. This signifies that 

 under the action of electric sparks the reaction NH 3 = N" -t 3H is 

 reversible, consequently it is a dissociation, and in it a state of equili- 

 brium is arrived at. The equilibrium may be destroyed by the addition 

 of gaseous hydrochloric acid, HC1, because with ammonia it forms a solid 

 saline compound, sal-ammoniac, NH 4 C1, which (being formed from a 

 gaseous mixture of 3H, N, and HC1) fixes the ammonia. The re- 

 maining mass of nitrogen and hydrogen, under the action of the sparks, 

 -again forms ammonia, and in this manner solid sal-ammoniac is obtained 

 to the end by the action of a series of electric sparks on a mixture of 

 gaseous N, H 3 , and HC1. 14 Berthelot (1876) showed that under the 

 action of a silent discharge many non-nitrogenous organic sub- 

 stances (benzene, C G H 6 , cellulose in the form of paper, resin, glucose, 

 C 6 H 10 O 5 , and others) absorb nitrogen and form complex nitrogenous 

 compounds, which are capable, like albuminous substances, of evolving 

 their nitrogen as ammonia when heated with alkalis. 15 



nitrogen changes in its properties ; if not permanently like oxygen (electrolysed oxygen or 

 ozone does not react on nitrogen, according to Berthelot), it may be temporarily at the 

 moment of the action of the discharge, just as some substances under the action of heat are 

 durably affected (that is, when once changed remain so for instance, mercuric oxide is 

 decomposed, white phosphorus passes into red, &c.), whilst others are only temporarily 

 altered (the dissociation of S 6 into S 2 or of sal-ammoniac into ammonia and hydrochloric 

 acid). Such a proposition is favoured by the fact of nitrogen giving two kinds of spectra, 

 with which we shall afterwards become acquainted. It may be that the molecules N 2 

 tin 'ii give less complex molecules, N containing one atom. Probably under a silent 

 discharge the molecules of oxygen, O 2 , are partly decomposed and the individual atoms 

 O combine with O.>, forming ozone, O 3 . 



15 This reaction, discovered by Chabrie and investigated by Thenard, was only rightly 

 understood when Deville applied the principles of dissociation to it. 



14 The action of nitrogen on acetylene (Berthelot) resembles this reaction. A mixture 

 of these gases under the influence of a silent discharge gives hydrocyanic acid, CoH-j + N 3 

 -=2CNH. This reaction cannot proceed beyond a certain limit because it is reversible. 

 * 15 Berthelot successfully employed electricity of even feeble potential in these experi- 

 ments, which fact led him to think that in nature, where the action of electricity takes 

 place very frequently, a part of the complex nitrogenous substances may proceed from 

 the gaseous nitrogen of the air by this method. 



As the nitrogenous substances of organisms play a very important part in them 

 (organic life cannot exist without them), and as the nitrogenous substances introduced 

 into the soil are capable of invigorating its crops (naturally in the presence of the 

 other nourishing principles required by plants), therefore the question of the means 

 of converting the atmosphericV nitrogen into the nitrogenous compounds of the soil, or 



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