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Skinner, Ernest B. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XIV, Part I (1902)

Kahlenberg, Louis
Action of metallic magnesium upon aqueous solutions,   pp. [299]-312


Page 307


Kahlenberg-Action, of Mietallic Magmsiuwr, Etc.  307
  At my request Mr. W. R. IMott measured -the so-called sinr
gle differences of potential between magnesiumi and some of
the salt solutions in question. The measurements were made
against the normal calomel electrode, the potential of which
was taken to be    0.56 volts. He found that at 200 C. the
single potential between magnesium and NaCl solution, (2 gram-
mls. per liter) is +1.163 volts between magnesium and NaOH
(1 gram-mol per liter) + 1.111 volts; between magnesium and
KOH (1 gram-mol. per liter) + 1.140 volts; between magne-
sium and KOH (0.1 gram-mol. per liter) 1.105 volts; and be-
tween magnesium and M!&gSO4 (1 gram-mol. per liter) + 1.366
volts. Each result represents the average of four determmna-
tions in which different bars of rnagnesium were used. In the
sodium chloride solution the E. M. F. changes but slightly with
the time; in the caustic alkali solutions the E. IM. F. tends to
fall with lapse of time; while in the magnesiumrr sulphate so-
lution the R M. F. increases on standing.
  The explanation of the above described phenomena of the
action of metallic magnesium upon aqueous, solutions will now
be considered. In the case of the saline solutions one might
feel inclined to, assume that the salt acts, upon the water liber-
ating a certain amount of free acid which attacks the magnet-
sium resulting in the liberation of hydrogen and the formation
of a, normal or basic salt or hydroxide of magnesium, accord-
ing to the nature of the solution under treatment.1 This would
be an attemnpt to extend Lemoine's interpretation of the action
of magnesium upon aqueous solutions of its salts to all aqueous
saline solutions. As stated above there is ground for this ex-
planation in the case of salts of the heavy metals, whose aqueous
solutions, as is well known, have acid reactions indicating that
they are indeed slightly decomposed by water yielding free
acid.  But in the case of salts of Mg, Ca, Ba, S~r. K, Na, Li,
  'In the language of the dissociation theory, preferred by some, it
would mean that that in saline aqueous solutions from which magne-
sium liberates hydrogen more readily than from pure water, the salt
reacts upon the water slightly, liberating some free acid which in turn
is electrolytically dissociated yielding free hydrogen ions. The concen-
tration of hydrogen ions in such solutions would then be greater than
in pure water (which is supposed to be only slightly electrolytically
dissociated) and this would account for the more vigorous action of
magnesium upon saline solutions.


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