1384 
can accelerate or retard the formation of H, from 2H. This may 
be regarded as the cause for the different behaviour of sulphuric 
acid of different dilution. As the seattering decreases on increasing 
concentration of the acid, a catalytic action on the reaction 2H +H, 
might be attributed to the H,SO, or to one of ifs ions. Also the 
different behaviour of different metals may, at least for a part, be 
put to the account of the promotion or retardation of the formation 
of molecular hydrogen. 
As for the second condition, it is clear that only when the atomic 
hydrogen penetrates into the metal, there can take place scattering. 
That in this case there is not always scattering, however, is 
apparent from the behaviour of iron and other metals. CHarpy and 
Bonnerot’) observed, namely, that in case of electrolytic hydrogen 
generation at a box-shaped iron electrode, hydrogen of a pressure 
of more than 20 atmospheres was. found inside the electrode. It 
will also have to be assumed in this case that the hydrogen which 
penetrates into the metal as H is partly converted into H, im the 
metal. The resulting tension is evidently not able in the hard iron 
to make the metal seatter. Instead of this the hydrogen diffuses 
through the metal. That in metals as iron and nickel, at which 
hydrogen is electrolytically developed, there are tensions present in 
consequence of the dissolved hydrogen appears from the curling up 
of thin plates of these metals on electrolysis. In this the side at 
which hydrogen is generated or that which contains most hydrogen, 
is also the convex side. 
Amsterdam, December 1915. 
Chemical Laboratory of the University. 
Chemistry. — “‘/n-, mono- and divariant equilibria.” Vil. By 
Prof. F. A. H. SCHREINEMAKERS. 
(Communicated in the meeting of February 26, 1916). 
1. Some general properties. 
In our previous considerations we have found some general properties 
of the curves and the regions of a P,7-diagram, for instance: 
in a P,7-diagram always a same number of bundles is situated 
at the right and at the left of each bundle; 
in a P,7-diagram the number of bundles is always an odd one 
and three at least ; 
1) C R. 156 (1913) 394. 
