NITRIFICATION AND THE FERTILIZATION OF SOILS. 73 
which is opposed to the volatilization of the ammonia; I 
mean the conversion of ammoniacal salts into nitrates, 
which occurs in the superficial portions of those soils which 
present a suitable chemical composition, and are placed 
under the most favourable conditions of moisture and tem- 
perature. 
With respect to the conversion of ammonia into nitric 
acid, I proved satisfactorily in 1838 that this furnishes the 
most simple and conclusive explanation of the formation of 
the nitre beds. My opinions on this subject are at present 
admitted by the majority of chemists ; but if any doubt 
should still exist, the following results will suffice to remove 
them. When a mixture of bichromate of potash, concentra- 
ted sulphuric acid and sulphate of ammonia is heated in a 
retort, a large quantity of nitric acid distils over. On heat- 
ing a mixture of peroxide of manganese or peroxide of lead 
or minium and weak sulphuric acid in the presence of sul- 
phate of ammonia, the ammonia of the sulphate is equally 
converted into nitric acid, which passes over. 
In investigating the conversion of ammoniacal gas into ni- 
tric acid by its contact at a high temperature with the pe- 
roxide of manganese, I found that we possessed in this 
oxide a valuable agent for transferring indefinitely i\\Q oxy- 
gen of the atmosphere to the ammonia. MnO 2 by a first 
oxidation passes into the state of MnO, which the contact 
of air immediately converts into Mn 3 4 , which is again 
susceptible of oxidizing the ammonia. 
If we now compare the slow progress of nitrification in 
the northern provinces with the rapidity with which it re- 
sults in meridional countries, it will be conceived how much 
greater the expense in ammonia or in nitrogenous manures 
must be in the north than in the south. 
The Academy will probably attach some interest to the 
result of the experiments I have made in support of my 
opinion respecting the influence of nitrification upon the 
VOL. XIII. — no. i. 7 
