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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 308


308 Wisconsin Academy of Sciences, Arts, and Letters.
there is no experimental evidence upon which to base the as-
sumption that in their aqueous solutions there is any free acid
present. Moreover, an alkaline reaction is imwaxted to the so-
lutions of these salts by the magnesium soon after it has been
immersed in them, and yet this alkalinity does not interfere
with the evolution of hydrogen.2
  There are no facts upon which to base the assum~ption that
magnesium chloride in aqueous solution suffers greater hydro-
lytic decomposition  (of which free hydrochloric acid is one
ofithe products) than do the chlorides of calcium, barium and
strontium~ for instance; and yet, solutions of the last three
salts are acted upon but feebly by magnesium, while from the
magnesium chloride solution hydrogen is rapidly evolved. This
point is illustrated still more strikingly by the fact that solu-
tions of sodium and potassium chlorides are relatively strongly
attacked by magnesium.; what reasons are there to assume that
these salts are decomposed more by water than those of the
alkaline earth metals?  And again, would it be rational to sup-
pose that because KCl solutions attack magnesium more read'
ily than sodium. chloride solutions that the former salt is de
,composed more by water than the latter? But the difficulty of
-this mode of explanation becomes even greater in the case of
the non-saline solutions. So for instance the alcoholic solu-
tion is acted upon more vigorously than pure water, clearly
there is no chance for assuming free acid to be the active agent
in the case of this solution.'
  The idea that Mouraour advances in the case of solutions
of ammonium salts, namely, that the solubility of magnesium
hydroxide in them determines the liberation of hydrogen from
them by action of magnesium, might possibly be applied to
  2 According to the dissociation theory, such an alkaline solution would
contain less hydrogen ions than pure water, and yet hydrogen is evolved
faster from them than from water.
  iiIndeed from the standpoint of the dissociation theory one would
have to hold that the alcohol solution contains fewer hydrogen ions
than are present in pure water, and hence action ought to be less than
in the latter. Moreover from the point of view of this theory, magne-
sium ought to act rather less on solutions of magnesium salts, for the
presence of Mg ions would militate against the formation of more of
them. And again the difference of potential between magnesium and
an MgSO4 solution ought to be less than between magnesium and a
NaCl solution; the facts show that just the opposite is true.
I


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