220 IS NITRIC ACID FOOD FOR PLANTS ? 



If nitric acid be a constant and generally appreciable consti- 

 tuent of rain-water, it is obvious that we ought to find sensible 

 traces of it in the mother liquor remaining behind after the crys- 

 tallization of the salt. But Gobel did not observe the presence 

 of nitrates either in the water of the river or in the deposited 

 salt. 



In the water of the Artesian Well* of Grenelle ; in the water 

 of the Nile ;f in that of the Seine, which contains carbonate of 

 ammonia in dry seasons ; in the waters of the Thames, or of the 

 Rhine, no one has yet proved the presence of nitrates. 



We may assume, from these facts, that the nitric acid fur- 

 nished to the earth in Europe, by means of rain, is extremely 

 small in amount ; so that, even if the nitric acid formed by light- 

 ning exercise a favorable action on vegetation, still this influence 

 cannot be considered as a source of the nitrogen of plants. When 

 it is considered that the number of thunder-storms in a year does 

 not amount in some districts to above twelve on an average, and 

 in many to only eight, it must be obvious from this, that it would 

 be quite impossible to prove the presence of nitric acid in the 

 waters of rivers or of springs. 



Under the tropics, where thunder-storms are much more fre- 

 quent than with us, we might suppose that the quantity of nitric 



* Payen found in 10,000 parts of this water : — 



Carbonate of lime . - 680 



" magnesia - - - - 1*42 



" potash - - - - 2*96 



Sulphate of potash - - - - 120 



Chloride of potassium - - - - 109 



t Regrjt It found in 22 lbs. of water of the Nile : — 



Carbonate of lime - 5'30 



" magnesia - - - - 7*43 



Peroxide of iron ----- 053 



Chloride of sodium - - - - 4'77 



Sulphate of magnesia - 0*53 



Silica 1-06 



Alumina - - - - - - 1*59 



Extractive matter - - - - 53 



Carbonic acid - - - - - 12' 19 



33*93 Gramme* 



