NITRIFICATION IN ARABLE SOIL. 357 



tion into nitric acid be also attributed to tlie action of a ferment? 

 Pasteur urged the proi)riety of studying nitrification at tliis time. 



This was done by Boussingault in 1873,' In order to investigate the 

 tlieory of Kulibimnn that all that was necessary for the oxidation of 

 ammonia was the presence of air and a porous body, Boussingault 

 introduced into various porous materials, such as sand, chalk, and soil, 

 readily nitritiable nitrogenous substances, kept the mixture moist and 

 well ai'rated in order to favor nitritication, and after a certain time deter- 

 mined the nitrates formed. In the sand and the chalk the nitrogenous 

 materials did not undergo any transformation. In the soil, on the con- 

 trary, metamorphosis was rapid; /. c, nitrates did not appear in the first 

 two porous substances, but were abundant in the last. What, therefore, 

 did the soil contain which was lacking in the sand or the chalk ? Bous- 

 singault did not attempt to lind out. He was familiar, however, witli 

 the opinions of Pasteur, for he discussed the influence on the oxidation 

 of ammonia of microorganisms, which he styled "■' the fungi of Pasteur." 



It was not until 3 years later that the cause of this special action of 

 the soil was discovered by Schlcising and Miintz in the course of experi- 

 ments relating to the purification of sewage water by tiltration through 

 soil. In these experiments large cylinders, 2 meters high, filled with 

 soil, received the sewage under treatment. When the water filtered 

 slowly through the soil it was found that not only the solid materials 

 which were in suspension were removed, but also that the dissolved 

 substances were greatly modified. Although the original solution con- 

 tained ammonia salts derived from the fermentation of the sewage, the 

 Altered water contained no ammonia, but was charged with nitrates. 

 This observation simply confirmed those of Boussingault on the influ- 

 ence of soil on nitrification, and would hardly be worth describing if it 

 had not been the first step toward the important discovery which has 

 made the names of Schlosiug and Miintz illustrious. 



Some time before this Miintz had made the observation that chlo- 

 roform acts on all animal organisms, and especially that it benumbs 

 and paralyzes the activity of ferments. Profiting by this interesting 

 observation Schliising and :\liintz introduced into a cylinder used for 

 filtering sewage water a certain amount of chloroform, and afterwards 

 examined day by day the water which filtered through the soil. This 

 water was limpid from the first, but very soon the nitrates diminished 

 and finally disappeared, /. f., the chloroform completely checked nitri- 

 fication. Since chloroform acts only on living beings, it is evident 

 that if the chloroforming of the soil caused it to lose its nitrifying 

 properties nitrification must have been due, as Pasteur maintained, to 

 a true fermentation. It is possible to confirm this conclusion by other 

 tests. The microorganisms are destroyed by temperatures of 100 to 

 120° C. In other words, a soil loses its nitrifying properties when it 

 is sterilized or has all living organisms in it destroyed. If, however, 



' Ann. Chim. Phys., 29, ser, 4, p. 186. 



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