Ji66 tiow cuors yEtin. 



HI. 1000 grm?. of soil and 500 grms. marl acquired 0.002 grms. ammonia and 

 0.360 grms. nitric acid. 



IV. 1000 grms. of soil and 2 grms. carbonate of potash acquired 0.015 grms. 

 ammonia and 0.290 grms. nitric acid. 



V. 1000 grms. of soil and 200 grms. quiclilime acquired 0.303 grms. ammonia 

 and 0.099 grms. nitric acid. 



The unfavorable effect of caustic lime is well pronounc- 

 ed and is confirmed by other similar experiments. Car- 

 bonate of potash, which is strongly alkaline, but was used 

 in small quantity, and marl (carbonate of lime), which is 

 but very feebly alkaline, are plainly inferior to sand in 

 their influence on the development of nitric acid. 



The effect of lime or carbonate of potash in these ex- 

 periments of Boussingault may, perhaps, be thus explain- 

 ed. Many organic bodies which are comparatively stable 

 of themselves, absorb oxygen with great avidity in j^res- 

 ence of, or rather when combined with, a caustic alkali. 

 Crenic acid is of this kind ; also gallic acid (derived from 

 nut-galls), and especially pyrogallic acid (a result of the 

 dry distillation of gallic acid). The last-named body, 

 when dissolved in potash, almost instantly removes the 

 oxygen from a limited volume of air, and is hence used 

 for analysis of the atmosphere.* 



We reason, then, that certain organic matters in the 

 soil of Boussingault's garden, became so altered by treat- 

 ment Avith lime or carbonate of potash as to be susceptible 

 of a rapid oxidation, in a manner analogous to ^\•hat hap- 

 pens with pyrogallic acid. Dr. H. Angus Smith has shown 

 {Jour. Boy. Ag. /Soc, XVII, 436) that if a soil rich in or- 

 ganic matter be made alkaline, moist, and warm, putre- 

 factive decomposition may shortly set in. This is what 

 happens in every well-managed compost of lime and j^eat. 

 By this rapid alteration of organic matters, as we shall see 

 (p. 268), not only is nitric acid not formed, but nitrates 

 added are reduced to ammonia. It is not improbable that 



• Not all organic bodies, by any means, are thus affected. Li: 

 nlteration of urine, flesh, and the albuminoids. 



