CHEMICAL SCIENCE. 261 



ccption of manganese, which could be detected only in Nos. 3 and 4. The 

 bases were potash, soda, lime, magnesia, and peroxide of iron; the acids, 

 carbonic, silicic, nitric, sulphuric, phosphoric, and chlorine. Besides these 

 substances, there were also organic substance, clay and sand. 



In none of these residues could the presence of a soluble compound of 

 alumina or of ammonia be recognized. It was only by boiling for a long 

 time with concentrated caustic potash, that an ammoniacal reaction became 

 perceptible, and that was probably due to the decomposition of a nitrogenous 

 organic substance. There is, however, so large an amount of nitric acid 

 present, that when the residues of evaporation are heated upon platinum 

 foil, they deflagrate ; and when the solution is heated with sulphuric acid, it 

 decolorizes indigo solution. 



This nitric acid has most likely originated chiefly from ammonia by oxida- 

 tion ; for, although nitric acid may be produced directly by the combination 

 of atmospheric nitrogen with the oxygen condensed by the soil, ammonia 

 would always be oxidized first, and converted into nitrate of ammonia. 



However, since the nitric acid in the solution from soils exists in the state 

 of a lime or magnesia salt, this is a further proof of the powerful attrac- 

 tion of the soil for ammonia. So that while, on the one hand, the capability 

 of the soils to condense ordinary oxygen and ozonize it, may cause the pro- 

 duction of nitrate of ammonia, its powerful attraction for ammonia causes 

 the decomposition of the nitrate of ammonia, the base being retained by the 

 soil, while the nitric acid combines with lime or magnesia. 



The analyses show that one million parts of the water passing through 

 soil six inches deep contained: 



These analyses illustrated the absorptive power of soils, first pointed out 

 by Mr. Way as so important in its influence upon the nutrition of plants. 

 With one exception only, neither phosphoric acid nor ammonia were present 

 in sensible amount; the quantity of potash is in all instances small, and 

 principally referable to the organic substance in the solution. Chlorine, 

 sulphuric acid, and nitric acid salts are not retained by the soil. 



If these analyses show the substances that are dissolved from the soil, the 

 opinion that plants derive their nutriment from solutions must be given up. 

 The soils experimented upon gave good crops of corn and straw, and the 

 quantities of potash and phosphoric acid required by these crops much 

 exceed those which would be furnished by solutions of the above composi- 

 tion. Moreover, the comparison of the ash of cereals, and the substance 

 dissolved from the soil, is inconsistent with the opinion that the food of 

 plants is supplied in solution, unless they are supposed to possess a very 

 considerable selective power. Annalen der Chemie itnd Pharmacie, cvii. 27. 



