ACTION OF ELECTRICITY. 219 



traces are attributed by the majority of authors to the presence 

 of nitric acid 1 or other nitrogenous compounds in the atmosphere. 

 The appearance of ammonia in the reaction of the metals (iron, 

 zinc, arsenic, lead, tin) upon dissolved alkaline hydrates, appears 

 in the same way due to the existence of a trace of cyanides or 

 nitrates in these alkalis. 



6. Earthy substances. Mulder has asserted that during the 

 slow alteration of earthy substances, small quantities of ammonia 

 are formed. But quantitative measurements have not shown 

 that these quantities are capable of compensating the incessant 

 loss of nitrogen produced during vegetation. 



7. Hence the purely chemical reactions which take place in 

 nature seem insufficient to explain the incessant reproduction of 

 the nitrogenous combinations. 



Nevertheless, the latter does take place, but it results, in the 

 opinion of the author, from an energy foreign to purely chemical 

 actions. 



It is electricity which causes the fixation of free nitrogen, and 

 principally at the ordinary temperature and at the low tensions 

 which electricity possesses at the surface of the earth every- 

 where and at all times, even during the finest weather. 



Second Section. Actions of Electricity in general. 



1. Electricity can be employed under various forms to excite 

 chemical reactions, viz. voltaic current, electric arc, electric 

 spark, or silent discharge. The last-named mode of action may 

 itself be effected in several ways ; for instance, by suddenly 

 varying the potential, by the effect of rapid discharges, some- 

 times all in one direction, sometimes in alternate directions, or 

 again by maintaining the potential constant throughout the 

 whole duration of the experiment. Now it is certain, and this 

 is a fundamental fact, that all the modes of action of electricity, 

 with the exception perhaps of the voltaic current traversing 

 liquid electrolytes, bring about the chemical activity of nitrogen, 

 but in very different ways. Before reviewing them, let us decide 

 a preliminary question. 



2. Does there exist a special isomeric modification of nitrogen 

 analogous to ozone, which is the origin of the nitrated 

 compounds ? This is the point which the author has set him- 

 self to clear up. He has observed that the activity of nitrogen 

 is only called into play at the moment when this element is 

 submitted to the action of electricity. Pure nitrogen, however, 

 does not undergo appreciable permanent modifications either by 

 the action of the arc, or by that of the spark, or of the silent 

 discharge. In fact, nitrogen brought into immediate contact 

 with hydrogen at a distance of a few centimetres, by silent 

 discharge tubes, or by spaces in which it undergoes the action 



1 Cloez, " Comptes rendus," torn. lii. p. 527. 



