( 257 ) 
probable that decomposition occurs at higher temperature, we must 
give up the study of the remaining part of the 7>-figure. 
The salts which with water as second component will most likely 
behave as Na 2 S0 4 in connection with their retrogressive melting- 
point line are the sulphates of Ca, Cd, Ce, Fe, Gd, La, Mg, Mn, 
Nd, Ni, Pr, Sr, Th, Yb and Zn, and also the salts Li 3 CO t , Na 2 
Se 0 4 , ka s BP0 4 Ca Cr 0 4 . 
It is highly probable that the same peculiar behaviour will also 
often be found when we choose another solvent instead of water, 
in which it might be possible to extend the investigation over the 
whole of the region of concentration for salts with low melting points 
on account of the absence of secondary chemical actions. 
Anorg , Chem. Laboratory of the University. 
Amsterdam , Sept. 1909. 
Chemistry. — “On heterogeneous equilibria of dissociating com¬ 
pounds”. By Dr. F. E. G. Scheffer. Communicated by Prof. 
A. F. Holleman. 
On Dec. 30 th 1905 Dr. A. Smits published a communication on 
intersections of the plaitpoint curve and the three-phase curve of a 
dissociating binary compound in these Proceedings. In this paper 
some of the possible cases were discussed, the phenomena described 
which may be expected at such an intersection, and a further syste¬ 
matic discussion of the remaining possibilities announced. Prof. Smits, 
however, ceded the continuation to Prof. Roozeboom, who proposed 
it to me as a subject for my dissertation; I have only been able to 
profit by his guidance for a short time. I gladly avail myself of this 
opportunity to express my thanks to Prof. Smits for the assistance 
which he has given me in this investigation. 
The systems, for which intersection of the plaitpoint curve and 
the three-phase line of a dissociating binary compound occurs, may 
be arranged under the six following types. 
I. Both the critical end-points lie on the branch Ao; see fig. 1. 
This case was already discussed in the paper mentioned and illustrated 
by a combined PT- and ^-projection. 
II. One critical end-point lies on the branch the second on 
the branch SM, so between melting point and max. sublimation 
Point (points p x and q 2 from fig. 1). From an examination of fig. 2, 
which represents this case schematically, it will be clear, that the 
