( 204 y 



If WO now exainiiic the changes with rise of temperature, it is 

 noteworthy, as will i)resently become clear from the p-Mines, that we 

 have here to deal with changes quite analogous to those discussed in 

 the preceding paper. The three phase pressure lines e c .s and c^ e^ 6\ 

 approach each other and coincide at ECS. This coincidence takes 

 place at the maximum temperature of the 7>-Mine for the three phase 

 pressure. One of the two three phase i)ressure lines .s' e c and ^i ^i c, 

 must therefore pass through the positions indicated by e\c\ and e'c', 

 before it coincides with the other. Now it follows from the three phase 

 pressure line e\ c\ that the gas phase e\ has the same concentration 

 as the solid combination, while the liipiid phase c\ has another 

 concentration. The three phase pressure line e' c' on the other hand 

 indicates, that the liquid phase c' and the solid phase have the same 

 concentration, while the gas phase e' has another concentration. 



We see therefore, that the three phases solid-liquid-gas have not 

 the same concentration at any pressure, but that they become two 

 and two equal. We may express this also in this way : When a 

 combination dissociates in the liquid and the gas state, then this 

 combination has no longer a tri^jlepoint, for this point has split up 

 into two other points where vapour and solid respectively liquid 

 and solid get the same concentration. 



After I had written this paper, I found to my surprise, that 

 already in 1897 van der Waals had arrived at the same result by 

 a way which I intended to discuss later on and for which the diagrams 

 had been already drawn ^). 



4. In order to make the difference between a non-dissociating 

 and a dissociating combination more apparent, we consider the case, 

 that we bring the dissociating combination AB In solid condition 

 into a vacuum, and make the temperature rise continually. 



The solid substance AB will, when the volume is not too large, 

 coexist with its vapour, till the pressure has become equal to that 

 indicated by the point ö/; at this moment a third phase appears, 

 viz. liquid. As the total concentration must always be that of AB, 

 it is necessary that the concentration of the vapour phase lies on 

 one side, and that of the liquid phase on the other side of the line 

 for AB; as follows from the figures 4, 5 and 6 this is really the 

 case. With rise of temperature three phases continue to exist for 

 some time side by side and the va[)Our and liquid phases coexisting 

 with solid AB lie on the same horizontal line. The liquid phase 

 lies on the liquid branch c' c/ and the vapour phase on the vapour 



i) Verslag Koninkl. Akad. 21 April 1897, 482. 



