( 9 ) 



make C smaller than A'. In a copper-sal t-soliition e.g. this can very 

 easily be done, as is known, by addition of /vCxV, which in consequence 

 of the formation of the complex-ions \Cu^{CjSI)^' , causes copper-ions 

 to be extracted from the solution. The solution, which at tirst had a 

 ]iegative charge compared with the metal copper, loses this charge 

 completely by the addition oï KCN, and receives then a positive charge. 



In the above I think I have demonstrated the expediency of 

 replacing the vague idea "elektrolytische Lösungs-tension" by the 

 sharply detined idea solubility of metiil ions. 



Amsterdam, April 190G. Anory. Chem. Lah. of the University. 



Physics. — "(M the course of the P,T-curv€s for constant concentra- 

 tioii for the equilihrium solid-fluid.'' By Dr. A. Smits. (Commu- 

 nicated by Prof. J. D. van der Waai.s.) 



(Communicated in the meeting of April 27, 190G). 



In connection with my recent investigations it seemed desirable 

 to me to examine the hidden connection between the sublimation 

 and melting-point curves for constant concentration, more particularly 

 when the solid substance is a dissociable compound of two com- 

 ponents. This investigation offered some difficulties, which I, 

 however, succeeded in solving by means of data furnished by a 

 recent course of lectures giving by Prof, van der Waals. Though 

 his results will be published afterwards, Prof, van der Waals allowed 

 me, witli a view to the investigations wdiich are in progress, to use 

 that part that was required for my purpose. 



In his papers published in 1903 in connection with the investi- 

 gation on the system ether-anthraquinone ^) van der Waals also 

 discussed the F, 7-lines for constant ,/; for the equilibrium between 

 solid-fluid ^), and more particularly those for concentrations in the 

 immediate neighbourhood of the points p and cj^, where saturated 

 solutions reach their critical condition. 



Then it appeared that the particularity of the case involved also 

 particularities for the P, 7'-line, so that the course of the P, J'-line 

 as it would be in the usual case, was not discussed. 



i) These Proc VI p. 171 and p, 484 Zeitschr. f. pliys. Chem. 51, 193 and 52, 

 587 (1905). 



2) These Proc. VI p. 230 and p. 357. 



