775 



occurs for instance in tlie systems: Z -\- waiev -\- alcohol, wherein 

 Z represents an anhydric single, salt, which is not-volatile. 



For fixing the ideas we assume that B is the component, which is 

 not-volatile (fig. 1), so that .1 and 6' represent tiie volatile components. 



Now we imagine in fig. 1 curve pq to be omitted, so that the 

 curves ed and rs rest only, ed is the licpiidcurve of the region /> — 6-', 

 ?'.s' is the saturationcurve under a constant pressnre of the snbstance 7^. 



We can, in order to obtain the different diagrams, act in the same 

 way as we did before in the general case, or as in communication 

 XIII. For this we consider the movement of the curves ed and rs 

 with respect to one another on decrease of pressure. 



As wo assume that B is not volatile, these considerations are 

 not true, therefore, for points situated in the vicinit^^ of i?. Equilibria 

 situated in the immediate vicinity of B have viz. also always the 

 substance B in their vapour, so that the considerations of com- 

 munication XllI apply to these. 



When we decrease the pressure, the liquidcurve ed (fig. 1) shifts 

 further into the triangle towards the point B, so that under a definite 

 pressure the curves ed and rs meet one another. Now we distinguish 

 three cases. 



1. We assume that the curves ed and rs meet one another first 

 in a point on one of the sides of the triangle; when this takes place 

 on side BC, then consequently the points e and ?■ coincide in fig. 1, 

 while the two curves have no other point in common further. On 

 further decrease of B, this intersecting point shifts within the triangle 

 and it disappears at last on the side AB, when in fig. 1 the points 

 s and (/ coincide. Curve ed is situated then inside the sector Brs 

 and curve rs inside the region CedA. 



From this follows that the saturationcurve of B under its own 

 \'apourpressure can be represented bj' curve hahii in fig. 4, in which 

 the arrows indicate the direction, in which the vapourpressure increases. 

 The corresponding vapourcurve is the side CA; the liquid h viz. is 

 in equilibrium with the vapour C, liquid n with the vapour A and 

 with each liquid {a and h) of hn a definite vapour {a^ and b^) of CA 

 is in equilibrium. It follows from the deduction that the threephase- 

 triangles {B<ia^, Bbh^) turn their sides solid-gas towards the point It 

 and their sides solid-liquid towards the {)oint ti. 



This fig. 4 is a peculiar case of fig. 2 (XIII); when we suppose 

 viz. that the substance B does not occur in the vapour, curve A//i/;i«i 

 of fig. 2 (XIII) must coincide with the side CA of the triangle and 

 fig. 4 arises. 



