( 200 ) 



5. Fig. 9 represents tlie most interesting part of the projection of 

 the p-^.i'-space diagram on the ^>-7'-plane for the case that the plait- 

 point curve meets the sohibilitj curve, as with ether and anthra- 

 quinone. In this fig. the possibility has moreover been assumed, 

 that the second plaitpoint temperature t^ of a saturated solution lies 

 above the triplepoint temperature t„. Fig, 10 represents for this case 

 the 2>.i'-sections corresponding with tlie temperatures t^ and t^ (see 

 fig. 9). 



The section for t^ differs from the second section in Fig. 2 only 

 in this, that the liquid branch passes continuously into the vapour 

 branch with the point K as plaitpoint. If we now pass on to lower 

 temperatures, the downmost three phase pressure becomes smaller 

 and the upmost greater, while the plaitpoint pressure diminishes. In 

 consequence of these last two changes the points e, c and K get 

 nearer and nearer to each othei-, and when we haxe descended to 

 the temperature f.,, the points e, c and /v have coincided or in other 

 words the upmost three phase pressure has become a plaitpoint 

 pressure; this circumstance is accounted for in the p-'^'-section, corre- 

 sponding with the temperature t^ (Fig. 10). 



At the temperature f^, the triplepoint temperature, for wdiich no 

 ^;.^i>.gection is drawn here, because it immediately follows from that 

 for t^, tlie remaining downmost three phase pressure has become 

 triplepoint pressure, and the points e\, c\ and //j have coincided. 



Below this temperature the /Mf-sections over a certain temperature- 

 range consist only of a solubility isotherm of the shape of e\ qf\ 

 in Fig. 10, as has been discussed before. 



That the case assumed in Fig. 9 is not often to be realized, is 

 obvious, but that it is a possible case, is, in my opinion, not doubtful 



Amsterdam, June 1905. Chemical Laboratory of the University. 



Physics. — ''Contribution to the knowledge of the px- and the pT- 

 Unes for the case that two substances enter into a combination 

 which is dissociated in the liquid and the gasphase." By Dr. 

 A. Smits. (Communicated by Prof. J. D. van der Waals). 



The purpose of the following paper is to give a connected repre- 

 sentation which is in logical connection with the p,a;,^diagram which 

 has been recently drawn up by Bakhuis Roozeboom and in which it is 

 assumed that only the components can occur as solid phases, for the 

 most important particularities of the equilibria between a vapour, 



