H now CROPS PEEf). 



tricity directly, but the ozone developed by it, accom- 

 plishes this oxidation. It has long been known that nitric 

 peroxide decomposes with water, yielding nitric and ni- 

 trous acids thus : 



2 NO, + HP = NO^H + NO^H. 



It is further known that nitrous acid, both in the free 

 state and in combination, is instantly oxidized to nitric 

 acid by contact with ozone. 



Tims is explained the ancient observation, first made by 

 Cavendish in 1784, that when electrical sparks are trans- 

 mitted through moist air, confined over solution of potash, 

 nitrate of potash is formed. (For information regarding 

 this salt, see p. 252.) 



Until recently, it has been supposed that nitric acid is 

 present in only those rains which accompany thunder- 

 storms. 



It appears, however, from the analyses of both Way and 

 Boussiugault, tliat visible or audible electric discharges 

 do not perceptibly influence the proportion of nitric acid 

 in the air; the rains accompanying thunder-storms not 

 being always nor usually richer in this substance than 

 others. 



Von Babo and Meissner have demonstrated that silent 

 electrical discharges develop more ozone than flashes of 

 lightning. Meissner has shown that the electric spark 

 causes the copious formation of nitric peroxide in its im- 

 mediate path by virtue of the heat it excites, Avhich in- 

 creases the energy of the ozone simultaneously produced, 

 and causes it to expend itself at once in the oxidation of 

 nitrogen. Boussiugault informs us that in some of the 

 tropical regions of South America audible electrical dis- 

 charges are continually taking place throughout the whole 

 year. In our latitudes electrical disturbance is perpetu- 

 ally occurring, but equalizes itself mostly by silent dis- 

 charge. The ozone thus noiselessly developed, though 

 operating at a lower temperature, and therefore more 



