Skinner, Ernest B. (ed.) / Transactions of the Wisconsin Academy of Sciences, Arts and Letters
volume XIV, Part I (1902)
Action of metallic magnesium upon aqueous solutions, pp. -312
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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