117 



Contributions to the knov^ledge of the nitrogenous compounds 

 of arable soil, Berthelot and Andre {('ompt. rend., llii (liS'Jl), j>. 

 ISO). — In previous iiivesti^utioiiH* the authors have studied the forma- 

 tion of ammonia in ordinary cmltivatod soil free from eonsiderahle 

 quantities of vegetable mold. Such soils contain extremely little ready- 

 formed ammonia or ammonium salts, their nitrogen being largely in the 

 form of amide like eomi)onnds which yield ammonia gra«liially liy treat- 

 ment with acids or dilute alkalis, cold or hot, and even l)y treatment 

 with water at ordinary temperature. These amides are the source of the 

 ammonia ordinarily found in the analysis of soil. The same gradual 

 (U'C()mi)t)siti()n by water and by alkaline and earthy carbonates gives rise 

 to the ammonia which is emitted by cultivated soils and diffused through 

 the atmosphere. The amide substances which are thus decomposed 

 may be divided into three classes: (1) Amides i)roi)er, which are formed 

 by the union of acids with ammonia and from which ammonia is more 

 or less readily evolved by the action of acids and alkalis ; (2) alkal- 

 amides which are formed by the union of volatile nitrogenous bases 

 with acids, comport themselves similarly to the amides, and yield vola- 

 tile nitrogenous compounds; (li) alkalamides which are formed by the 

 union of non-volatile nitrogenous bases or allied bodies with acids, and 

 in being decomposed yield non-volatile nitrogenous products. Of 

 these alkalamides, some are soluble in water, others are insoluble. 

 The soluble ones when broken up by acids or alkalis may yield prod- 

 ucts, acid or alkaline, which are soluble, or those which are insoluble 

 in water. Similar distinctions apply to the nitrogenous organic 

 compounds of ordinary cultivated soil. A knowledge of thera is 

 indispensable for the inter[)retatiou of the analysis of the soil and the 

 understanding of its constitution ; nor can it be doubted that they are 

 important factors in the absorption of nitrogenous and carbonaceous 

 compounds of the soil by the plant, and in vegetable nutrition generally. 



In the study of a clay soil, it was found that the ratio of the organic 

 carbon to the nitrogen was such as would correspond to one part of 

 albuminoid material with three parts of humic or allied compounds, 

 such as are derived from carbohydrates. It is to be expected that the 

 researches of Schiitzenberger on the constitution of proteids may throw 

 light upou that of the nitrogenous compounds of the soil. 



The authors have studied the changes produced in the nitrogenous 

 compounds of soil by the action of acids and alkalis of ditferent degrees 

 of concentration, at ditferent temperatures, and during ditlVrent inter- 

 vals of time. They determined in each case the amounts of nitrogen 

 (1) disengaged as ammonia or other volatile alkaline compounds; (2) 

 remaining in non-volatile comitounds soluble in water; and (3) remain- 

 ing in insoluble compounds. In a number of cases they also determined 

 the amount of carbon in each of these compounds. With a cold 



"Ann. Cbim. et Phys., G ser., 11 (18ti7), p. 269. 



