72 NITRIFICATION AND THE FERTILIZATION OF SOILS. 
When a nitrate, the metal of which is precipitated by 
zinc, nitrate of copper for instance, is placed in presence of 
a mixture of zinc and hydrochloric acid, for every equiva- 
lent of zinc dissolved there is one equiv. of copper precipi- 
tated, and one equiv. of the nitric acid of the nitrate is con- 
verted into one equiv. of ammonia, the whole without any 
liberation of hydrogen. 
By passing a current of sulphuretted hydrogen through a 
solution of chloride of antimony mixed with a nitrate, the 
acid of this latter is converted into ammonia. Similar meta- 
morphoses are effected by the contact of nitrates with a 
solution of sulphuret of arsenic in potash, or with the hy- 
drated protoxides of tin and iron. 
I think that, after the announcement of these facts, no 
doubt can remain relative to the decomposition which the 
nitrates experience in the soil under the influence of putrid 
fermentation. It is known that this fermentation, considered 
as a deoxidizing agent, is capable of overcoming the strong- 
est affinities. 
If the fertilizing agent must be presented to the plant 
principally, if not exclusively, in the state of carbonate of 
ammonia, serious inconveniences arise from the volatile 
nature of this salt: for it is no sooner confided to the soil to 
fertilize it, than a large portion is removed by the air to be 
diffused over the earth. 
We have now to examine what influence nitrification 
has upon vegetation. It is conceivable that the mode of 
fertilization by the ammonia of the atmosphere may suffice 
for certain countries, and not for others ; the more we ap- 
proach the meridional countries, the less necessity is there 
for manures. 
If I entertain the conviction that the nitrates do not act 
generally as fertilizers, except after having experienced, at 
a certain depth in the soil, a decomposition which yields 
carbonate of ammonia, I am not the less satisfied that the 
fertility of the soils likewise depends on an inverse reaction, 
