296 AMMONIA AND NITRIC ACID. 



being placed either in a weak solution of pure ammonia, 

 or in a confined space with amnioiiiacal gas, or over 

 carbonate of ammonia, is then dried and exposed in 

 thin layers in this dry state to the air for fourteen days, 

 all the ammonia not intimately combined in the soil is 

 evolved, and the same result may be produced by con- 

 stant washing with cold water. Now if soils thus satu- 

 rated, the ammonia of which has been accurately ascer- 

 tained, are exposed to distillation with soda lye, it is 

 found that a considerable portion of the absorbed am- 

 monia is not separable in this way. In the following 

 table, A expresses the quantity of ammonia respectively 

 absorbed by various soils at the ordinary temperature 

 of the air ; B, the quantity of ammonia retained by the 

 same soils after twelve to fifteen hours' action of soda 

 lye in a water bath. 



One million milligrammes ( = 2'2 Ibs.) of soil from 



Havannah. Schleissheim. Bogenhausen. Clay soil. 



milligr grs. milligr. grs. milligr. grs milligr. grs. 



A Ammonia... 5520 85 3900 = 60 3240 = 50 2600 = 40 



B " ... 020-14 970=15 990=15 470= 7 



Under these circumstances, it appears that the 

 power of retaining a certain portion of the absorbed 

 ammonia is very unequal ; the Havannah earth (a poor 

 lime soil) retains a sixth of the absorbed ammonia, the 

 soil at Schleissheim the fourth, that at Bogenhausen 

 almost a third.* 



* We need not be surprised at this peculiar comportment, for it merely 

 proves that part of the ammonia in the earth is contained in an entirely 

 different form from that of a salt. The salts of ammonia are combinations 

 of ammonium, which can be easily decomposed by alkalies, alkaline earths, 

 and metallic oxides, the alkali taking the place of oxide of ammonium, or 

 the ammonium being displaced by some other metal. But we have no 

 reason to believe, that the ammonia, which by physical attraction is fixed 

 in the porous arable soil, yields its place to another body, and is separable 

 by it, if the latter has not a stronger attraction for the soil. 



Carbonate of lime, in the cold, produces scarcely any effect upon sul- 

 phate of ammonia ; but in an arable soil, which contains carbonate of lime, 

 the salt of ammonia is completely decomposed : lime takes the place of the 

 ammonia, the latter however does not become free, but enters into some 

 other combination, upon which lime has no effect. 



