Chemistry. — “The Electromotwe Behaviour of Magnesium’. 1. 
By Prof. A. Smits and R. Pa. Beck. (Communicated by Prof. 
P. ZEEMAN.) 
(Communicated at the meeting of Dec. 18, 1920). 
As was stated before magnesium closely resembles aluminium in 
its electromotive behaviour. Also the pure magnesium is as a rule 
a state disturbed in a noble direction, which reaches internal equi- 
librium by the absorption of small quantities of mercury; but in 
this case with magnesium these phenomena are weaker than with 
aluminium. 
Our purpose was to examine the electromotive behaviour of mix- 
tures of magnesium and mercury of different concentration in order 
to be able to set forth still more clearly the particular influence of 
small quantities of mercury. 
Before proceeding to this research, it was desirable to determine 
the melting-point diagram of the system Mg —Hg, which investigation 
was attended with several difficulties, which we will, however, not 
discuss here. The result to which this research led, is represented 
in the adjoined 7,N-figure. It must be pointed out here that this 
system had already been examined on the Hg-side by L. Campi and 
G. Sprroni'), but that this research had been discontinued at the 
very point where the difficulties set in, and the system becomes 
most interesting. 
We see from our diagram, which represents the situation of the 
melting-point lines under the varying vapour pressure, that the 
system Mg—Hg is very complicated, and contains several compounds. 
In order to ascertain what corrections must be applied in the 
concentration, in connection with the mercury in the vapour phase, 
the determination of the vapour tension of the different mixtures 
was undertaken, in which use was made of a glass spring indicator. 
This investigation, which is now being continued with the mixtures 
rich in mercury, however, yielded the result that for mixtures from 
0 to 50 at. °/, Hg the vapour tensions are very small, even up to 
the final temperatures of fusion. 
1) Atti della R. Accad. dei Lincei 24, 734 (1915). 
