00 now CROPS FEED. 



until in some way chemically decomposeil, belongs to the 

 soil or to the rivers and seas, 



Mtrous Acid in the Atmospheric Waters. — In most of the researches up- 

 on the quantity of nitric acid in tlie atmosphere and meteoric waters, 

 tdtruus acid has not been specially i-egarded. The tests which serve to 

 detect nitric acid nearly all apply equally well to nitrous acid, and n» 

 di.-criiuiuatiun has been made until recently. According to Schonbein 

 :md Bublig, nitrates are sometimes absent from rain-water, but nitrites 

 never. They occur, however, in but minute proportion. Pincus and 

 Rollig observed but traces of nitrous acid in the waters gathered at 

 Iiistcrburg. Reichardt found no weii^hable quantity of nitrous acid in 

 a samjile of hail, the water from which contained in 10 million parts, 33 

 parts ammonia and 5}4 parts of nitric acid. It is evident, then, that 

 nitrous acid, if produced to any extent in the atmosphere, does not re- 

 main as such, but is chiefly oxidized to nitric acid. 



In any case our data are probably not incorrect in respect to the 

 quantity of nitrogen existing in both the forms of nitrous and nitric 

 acids, although the former compound has not been separately estimated. 

 Tlie methods employed for the estimation of nitric acid would, in gen- 

 eral, include the nitrous acid, with the single error of bringing the latter 

 into the reckoning as a part of the former. 



IVitric Acid as Food of Plants. — A multitude of obser- 

 vations, both in the field and laboratory, demonstrate that 

 nitrates greatly promote vegetable growth. The extensive 

 use of nitrate of soda as a fertilizer, and the extraordinary 

 fertility of the tropical regions of India, whose soil until 

 lately furnished a large share of the nitrate of potash of 

 commerce, attest the fact. Furthermore, in many cases, 

 nitrates have been found abundantly in fertile soils of tem- 

 perate climates. 



Experiments in artificial soil and in water-culture show 

 not only that nitrates supply nitrogen to plants, but dem- 

 onstrate beyond doubt that f/te^ alone are a sufficient 

 source of this element, and that no other compound is so 

 well adapted as nitric acid to furnish crops with nitrogen. 



Like ammonia-salts, the nitrates intensify the color, and 

 increase, both absolutely and relatively, the quantity of 

 nitrogen of the plant to which they are supplied. Their 

 effect, when in excess, is also to favor the development of 

 foliage at the expense of fruit. 



