ATMOSPIIKUIC AlU AS THE FOOD OF PLANTS. 77 



slowly than that wlilch is produced by lightning, must 

 really oxidize much more nitrogen to nitric acid than the 

 latter, because its action never ceases. 



Formation of \itro^CD Compounds in the Atmosphere. 



— h. From tree nitrogen (by ozone ?) in the processes of 

 combustion and slow oxidation. 



At high temperatures. — Saussure first observed {Ann. 

 de Chimie., Ixxi, 'IS'l), that in the burning of a mixture of 

 oxygen and hydrogen gases in the air, the resulting water 

 contains .-immonia. He hud previously noticed that nitric 

 acid and nitrous acid are formed in the same process. 



Kolbe {Ann. CJiem. u. Pharm., cxix, 176) found that 

 when a jet of burning hydrogen was passed into the neck 

 of an open bottle containing oxygen, reddish-yellow va- 

 pors of nitrous acid or nitric peroxide were copiously pro- 

 duced on atmospheric air becoming mingled with the 

 burning gases. 



Bence Jones {Phil, Trans.., 1851, ii, 399) discovered ni- 

 tric (nitrous?) acid in the water resulting from the burn- 

 ing of alcohol, hydrogen, coal, wax, and purified coal-gas. 



By the use of ttie iodide-of potassium-starch test (Price's 

 test), Boettger {Jour, far Prakt. Chem., Ixxxv, 396) and 

 Schonbein (ibid., Ixxxiv, 21.5) have more recently confirm- 

 ed the result of Jones, but because they could detect 

 neitlier free acid nor free alkali by the ordinary test-pa- 

 pers, they concluded that nitrous acid and ammonia are 

 simultaneously formed, that, in fact, nitrite of aw.monia 

 is generated in all cases of rapid combustion. 



Meissner ( Untersuchumjen Tiber den Sauerstoff^ 1863, p. 

 283) was unable to satisfy himself that either nitrous acid 

 or ammonia is generated in combustion. 



Finally, Zabelin {Ann. Chem. x. Ph., cxxx, 54) in a 

 series of careful experiments, found that when alcohol, il- 

 luminating gas, and hydrogen, burn in the air, nitrous acid 

 and ammonia are very frequently, but not always, formed. 



