248 nq\y chops pked. 



acids, wlicrel)}' hoJies result which arc no h)nger soluble 

 in Avator, and which, as such, arc probably innutritions to 

 plants. These substances are quite slowly decomposed 

 when put in contact, especially when heated with alkalies 

 or caustic lime in the presence of water. In this decom- 

 jjosition ammonia is reproduced. These indifferent nitrog- 

 enous matters appear to be analogous to a class of sub- 

 stances known to chemists as amides, of Avhich asparagin, 

 a crystallizable body obtained from asparagus, young peas, 

 etc., and urea and \iric acid, the characteristic ingredients 

 of urine, are examples. Further account of these matters 

 will be given subsequently, p. 376. 



Quantity of Ammonia in Soils. — Formerly the amount 

 of ammonia in soils Avas greatly overestimated, as the re- 

 sult of imperfect methods of analysis. In 1846, Krocker, 

 at Liebig's instigatiim, estimated the nitrogen of 22 soils, 

 and Liebig published some ingenious speciilations in which 

 all this nitrogen was incorrectly assumed to be in the form 

 of ammonia. Later, various experimenters have attempt- 

 ed to estimate the ammonia of soils. In 18."35, the writer 

 examined several soils in Liebig's laboratory. The soils 

 were boiled for some hours Avith water and caustic lime, 

 or caustic potash. The ammonia that Avas set free, distill- 

 ed off, and its amount Avas determined by alkalimetry. 

 It Avas found that however long the distillation was kept 

 up, ammonia continued to come over in minute quantity, 

 and it Avas probable that this substance Avas not simply 

 expelled from the soil, but Avas slowly formed by the ac- 

 tion of lime on organic matters, it being Avell known to 

 chemists that many nitrogenous bodies are thus decom- 

 posed. The results Avere as follows : 



White sandy loam distilled with caustic lime gav« 



Yellow clav " •' " ' " " -'00047 



iciiowciay (0.0051 



" " " " " potash " " one " 0.0075 



Black garden soil " " " lime " " ♦wo *' \ o 0951 



