Kohlenberg—Action of Metallic Magnesium , Etc. 307 
At my request Mr. W. E. Mott measured the so-called sin¬ 
gle differences of potential between magnesium) 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 20° O. the 
single potential between magnesium and HaCI solution (2 gram- 
nfols. per liter) is +1.163 volts between magnesium! and HaOH 
(1 gram-mot 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 MgS0 4 (1 gram-mol. per liter) +1.366 
volts. Each result represents the average of four determina¬ 
tions in which different bars of mjagnesium were used. In the 
sodium chloride solution the E. M. E. changes but slightly with 
the time; in the caustic alkali solutions the E. M. E. tends to 
fall with lapse of time; while in the magnesium sulphate so¬ 
lution the E. M. E. 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 magne¬ 
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 attempt 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 1 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, Sr. K, Ha, Li„ 
i.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 el'ectrolytically dissociated yielding free hydrogen ions. The concen¬ 
tration of hydrogen ions in such solutions would then he greater than 
in pure water (which is supposed to he only slightly electrolytically 
dissociated) and this would account for the more vigorous action of 
magnesium upon saline solutions. 
