268 OW CROPS FEED. 
phere (p. 167) indicate absorption both of oxygen and 
nitrogen, as well as of carbonic acid. The fact that char- 
coal acts as an energetic oxidizer of organic matters has 
been alluded to (p. 169). This action is something very 
remarkable, although charcoal condenses oxygen but toa 
slight extent. The soil exercises a similar but less vigorous 
oxidizing effect, as the author is convinced from experi- 
ments made under his direction (by J. J. Matthias, Esq.), 
and as is to be inferred from the well-known fact that the 
odor of putrefying flesh, etc., cannot pass a certain thickness 
of soil. But charcoal is unable to accomplish the union 
of oxygen and nitrogen at common temperatures, or at 
212° F., either dry, moistened with pure water, or with 
solution of caustic soda, (Experiments in Sheffield labo- 
ratory, by Dr. L. H. Wood.) 
Putrefying flesh, covered with charcoal as in Stenhouse’s 
experiment (p. 169) gives off ammonia, but no nitric acid is 
formed. Dumas has indeed stated ( Comptes Rend., XXIII) 
that ammonia mixed with air is converied into nitric 
acid by a porous body—chalk—that has been drenched 
with caustic potash and is heated to 212° IF. But this is 
an error, as Dr. Wood has demonstrated. It is true that 
platinum at a high temperature causes ammonia and oxy- 
gen to unite. Even a platinum wire when heated to red- 
ness exerts this effect in a striking manner (Kraut, Ann. 
Ch. u. Ph., 136, 69); but spongy platinum is without cf- 
fect on a mixture of air and ammonia gas at 212° or lower 
temperatures. (Wood.) 
e. Presence of organic matters Yas to oxidation, Re- 
duction of nitrates to ammonia, etc., in the soil—As we 
have seen, the organic matters (humus) of the soil are a 
source of nitric acid. But it appears that this is not al- 
ways or universally true. In compact soils, at a certain 
depth, organic matters (their hydrogen and carbon) may 
oxidize at the expense of nitric acid itself, converting the 
latter into ammonia, Pelouze (Comptes Rendus, XLIV, 
