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Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XII, Part II (1899)

Copeland, Edwin Bingham; Kahlenberg, Louis
The influence of the presence of pure metals upon plants,   pp. [454]-474 PDF (5.5 MB)


Page 455


Metals and Plants.
the injury done the plant was of a different nature from ordi-
nary poisoning, and he proposed for the new phenomena the
name of "Oligodynamic effects".  His idea seemed to be,
that
from metallic copper minutest particles pass into solution, and
that these particles kill the plants by a different action from
that of toxic copper salts -perhaps by physical rather than
chemical means.' The phenomena of death of Spiro gyra by
oligodynanmic action are, as should be expected, different from
those when death is caused by much more concentrated copper,
introduced as a salt.
  The facts in NiAgeli's paper are final. But his theoretical ex-
planation appears to us improbable and unnecessary, and this
paper is a partial explanation of our disbelief.
   Every metal in contact with water and air is subject to some
 change. It reacts with the oxygen and carbonic acid dissolved
 in the water, or with the water itself, to form oxides, hydrox-
 ides, carbonates, basic carbonates, or acids, which in greater
 or less degree pass into solution. When this chemical action is
 sufficient for the effect to become visible, the metal is tarnished
 or corroded; and even gold and platinum lose their lustre.
 From common observation and scientific research it is known
 that many of the salts which form under such conditions are
 poisonous. Now, since the conditions are present under which
 salts form, and since the salts are known to be toxic, and since
 any kind of solutions of metals in the Metallic state is unknown
 to the chemist, it is a priori reasonable to suppose that the in-
 jury which a plant suffers in water in the presence of a metal,
 is due to the salts of the metal, just as much as if the salts, and
 not the metal, were introduced directly into the water.
    The injury to the plant will depend largely upon two factors:
    1. The tendency of the metal to get into solution as a compo-
  nent of chemical compounds -which we shall designate loosely
  as salts.
  I This seems to us to be a fair statement of the tenor of Ndigeli's work,
  and is the conclusion commonly drawn from him. Cf. Frank and Krftger
  (5), though Nageli does express the belief that the metals dissolve as
hy-
  droxides, or carbonates. The presence at some time of the metal itself
is
  repeatedly emphasized as necessary to produce oligodynamic effects.
455


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