312 AMMONIA AND NITEIC ACID. 



various kinds of soil in many cliiTerent lands and districts 

 shows that there is scarcely a single fruitful wheat soil 

 which does not contain at least 5000 to 6000 kilogrammes 

 ( = 98 to 118 cwt.) of nitrogen per hectare ( = 2^ acres) to 

 the depth of 25 centimetres ( = 10 inches) ; and the simplest 

 comparison of the quantity of nitrogen in the soil, with 

 that which is removed in the crops, proves that the 

 latter amounts to a very small fraction, and that the land 

 is exhausted of all other nutritive substances sooner than 

 of nitrogen. 



The experiments of Maj^er ('Ergeb. landw. u. agric. 

 Versuche.' MUnchen. Iter Heft, s. 129) show that the 

 behaviour of arable soil with respect to alkahes in watery 

 solution affords no conclusion as to the nature of the 

 nitrogenous compounds therein contained. It had been 

 assumed, that all nitrogen in the earth in the form of 

 ammonia could be separated by distillation with caustic 

 alkalies, and that the portion that was not thus separated 

 did not exist as such. Mayer proved the incorrectness of 

 this assumption ; he first discovered, that many earths 

 rich in humous constituents when boiled for four hoiu-s 

 (which may be considered equivalent to lixiviation for 

 four hoiurs with boihng water) still retained a very con- 

 siderable quantity of ammonia. The earths employed in 

 these experiments were (1) earth from the hollow trunk 

 of a tree, (2) garden soil rich in organic matters, from 

 the Botanic Garden, (3) strong clay soil from Bogen- 

 hausen. 



Ammonku 

 One million milligrammes ( = 2-2 lbs.) retained at the temperature of boiling water : 



mDligr. gi's. milligr. grs. milligr. grs. 



(1) Tree soil, 7308 = 112 (2) Garden soil, 4538 = 70 (3) Clay, 1576 = 24 



■ If an arable soil after saturation with ammonia, by 

 being placed either in a weak solution of pure am- 



