598 DR GEORGE WILSON ON NITRIC ACID, &c. 
white heat, assisted by platina,—or by chlorine and its congeners, with their affi- 
nities for hydrogen exalted by sunshine; but nitric acid is the frailest of oxides. 
It not only parts with oxygen to the immense majority of metals, and of metallic 
and organic compounds, but the simple application of heat deoxidises it; and sun- 
light, which so greatly intensifies the inherent deoxidising power of a plant, can, 
without the co-operation of its complex organic apparatus, compel nitric acid to 
undergo deoxidation. 
If, therefore, sunlight alone can deoxidise nitric acid, sunlight, co-operating 
with a powerful deoxidising apparatus, will not be less efficacious; and those 
chemists who declare that a plant can deoxidise water, carbonic acid, and sul- 
phuric acid, but cannot deoxidise nitric acid, are uttering the paradox, that the 
more easy the decomposition of an oxide is, the more difficult does a plant find it 
to be to decompose it; so that if it be exceedingly susceptible of deoxidation, then 
the plant, whose greatest chemical power is a deoxidising one, cannot deoxidise it 
at all. 
No one, I think, would articulately defend such a doctrine. The opposite con- 
clusion is surely the just one, that if nitric acid be conveyed into plants, it will be 
reduced by loss of oxygen finally to the condition of nitrogen, and as such be 
as available for the production of azotised vegetable compounds as the nitrogen 
of ammonia. 
Teachers of chemistry appear to be reluctant to admit two sources of nitrogen 
for plants, because it complicates their statements, and multiplies their formule ; 
but the partial representations of truth, to which all teachers are compelled, how- 
ever catholic in spirit, can never justify the expression of one-sided views, as the 
counterpart of the multiform unity of Nature. Those, moreover, who have been 
accustomed to trace back all azotised vegetable compounds to ammonia, need 
only postulate that nitric acid having been deoxidised into nitrogen, that element 
unites with hydrogen to form ammonia before any organic compound is developed ; 
and thereafter they may carry out the ammonia theory as before. Such a con- 
version of nitric acid into ammonia is not hypothetical, for it can be readily ef- 
fected by diluting the acid largely with water, and dissolving zinc in it. 
It would more consist-with the modesty of true science, to be less dogmatic 
than we generally are on the phenomena which occur within the inscrutable re- 
cesses of a living plant; and to admit the probability of its being able to employ 
as food various azotised, as well as other compounds. If, however, we are re- 
quired to reduce to its simplest chemical expression the conclusion which our 
present science warrants regarding the inorganic origin of the nitrogen so essential 
to plants, we must not say that only ammonia, or only nitric acid, is its source, 
but that both are; or, ina word, that the chief mineral or inorganic representa- 
tive and parent of the nitrogenous constituents of plants and animals is the Nitrate 
of Ammonia. 
