754 



con cenl ration-diagram the liquid curve of the region L-G (curve Fl 

 in fig. 1) going through F, has in the P,J'-diagram the same tangent 

 in F as the evaporationline of the liquid F starting from F. 



If we compare the P,T-diagram of the solutionpaths of a binary 

 compound F (fig. 2) with those of a ternarj^ compound P [fig. 4 (IV) 

 and 1-3 (V)], then we see very great differences in the vicinitj- 

 of the point F. We find these differences also in the concentration - 

 diagrams. When viz. in fig. 1. in the point F we construct tangents 

 to the curves Fl, Fk and Fs going through the point F, three 

 different tangents arise. If P is a ternary compound, as e. g. in 

 fig. 1 (IV), then these curves touch one another in F and the three 

 tangents coincide in the line XFY. 



All this is based on the following. When P is a binary compound, 

 a new substance must be added, in order to trace a ternary solution- 

 path from F. When, however, F is a ternary compound, we add no 

 new substance in order to trace a solutionpath, from F, but substances, 

 which are already present in the melted F. 



{To he continued). 



Physics. "An apparatus for the determination of gas isotherms up 

 to about 3000 aims." Van dkr WAALs-fund researches N". 5. 

 By Prof. Ph. Kohnstamm and K. W.Walstra. (Communicated 

 by Prof. VAN der Waals). 



(Communicated in the meeting of December 27, 1913). 



As is known the material for testing the theory of the equation 

 of state at very high pressures consists almost exclusively of what 

 Amagat has published in his famous papers. It seems desirable for 

 different reasons to extend this material. Quite apart from the desirability 

 to get to know the behaviour of other gases than those examined 

 by Amagat — we think in the first place of the mon-atomic gases — 

 Amagat's work itself gives rise to different questions, which can 

 only be decided l)y means of new experiments. 



First of all it is known that Amagat does not give the direct 

 results of his observations; he only publishes the results of a graphical 

 interpolation between these observations. The question i-ises how 

 great the deviations are between the interpolated and the real 

 observations, and whether another way of interpolation had been 

 possible. Nor can the probable experimental error of Amagat's 

 observations be inferred from his experiments. And it has finally 



