( -■^' ) 



points of solutions saturated with solid B occur, one on branch ih 

 and anothei on branch la. At the last point, iioiling does not take 

 place on heating but on cooling. The f, ,<'-ligures at a constant 

 pressure have been deduced by me, and the phenomena, in solutions 

 of salts in water and of sulphur in carbon disulpliide, have been 

 demonstrated bv SitiTs and de Kock. 



The figures I, 3, 5, 6 show at once that this same case may 

 also occur in solutions saturated with a compound of the two com- 

 ponents as soon as their three-phase line shows branch lb as well 

 as la. -E.xamples of two boiling points of the saturated solution have 

 not thus far been noticed in binary compounds although they should 

 be far from rare. 



In compounds Avhere, among the saturated solutions, there is 

 present one with a minimum pressure (Fig. 3), a second boiling 

 point of the saturated solution might occur with solutions either 

 richer in A or in B ; in fact a third boiling point at the side of 

 the solution richer in B would be possible if the point D in fig. 3 

 were situated so low that, at the same pressure, the branches JJl\, 

 2\Ti and T^H could be intersected in succession. The saturated 

 solution would then in succession first disappear, then reappear to 

 finally disappear once more. Examples belonging to this case have 

 thus far not been sufficiently studied. 



If branch 3 of the three-phase hne exists for the solutions richer 

 in B {G D in Fig. 1 and Q, G H in Fig. 3 and 5), then if this 

 line is crossed, there occurs at a constant pressure a boiling |)oint 

 of the saturated solution of a different nature from that on branch 1. 

 The /, .r-figure of such a case is quite analogous to that derived by 

 me ') for saturated solutions of the component ^i whose Ihree-jihase 

 line in Fig. 1, 3, 5 always indicates branch 3. On boiling the solution 

 saturated with A the following transformation takes [)lace : 



solid -j- liquid — *• vapour. 



As solid and liquid now pass together into vapour in a definite 

 proportion, it now depends on the quantity of those two phases 

 which of the two disappears at the boihng point. Tiiis case occurs 

 for instance on the three-phase line for ice in systems of water and 

 little volatile substances as salts, also on the three-phase line for 

 solid CO, in mixtin-es of CO3 with less volatile substances such as 

 alcohol. 



The same must now also ser\e for compounds' in so far branch 3 

 occurs therein. Among the binary systems whose liquid-vapour pres- 



1) Heler. Gleichg. II. 341 et seq. 



