( 609 ) 



The curve Ac must therefore, be situated in the plane passing- 

 through AW and the point D of the side Li Am. The surface Li or 

 Ade indicates the liquid saturated with Li a S0 4 or Li 2 S0 4 H 3 0, or 

 with the above mentioned mixed crystals; it must, therefore, consist 

 of different parts which however, are not further indicated "in the 

 figure. At the temperature mentioned here (6°5) systems of two liquid 

 phases may occur also; in the figure these are represented by the 

 surface L l L i or b l K l b % K % which we may call the binodal surface; this 

 binodal surface is divided by the line K X K % into two parts L x and L s 

 in such a manner that each point of L x is conjugated with a point 

 of L % . Two conjugated points indicate two solutions in equilibrium 

 with each other : with each solution of the surface L x a definite 

 solution of the surface L 2 may be in equilibrium. 



Instead of a critical point, such as occurs with ternary mixt me- 

 at a constant temperature and pressure, a critical line is formed here, 

 represented by K 1 K i . Each point of this line represents, therefore, 

 a solution which is formed because in the system of two liquid 

 phases L l -f- L 2 the two liquid phases become identical. Let us now 

 look at the sections of the different surfaces: Ad then represents the 

 solutions saturated with LiNH 4 S0 4 as well as with Li 2 S0 4 H 2 0; Ab^ 

 and bj) indicate the liquids saturated with LiNH 4 S0 4 and (NH 4 ) 2 S0 4 . 



The intersection of the binodal surface with the surface Am namely, 

 the curve b 1 K l b 2 indicates the system: L, -J- L s + (NH 4 ) 2 S0 4 namely, 

 two liquid phases saturated with solid ammonium sulphate. With 

 each point of the curve b 1 K x a point of />J\\ is conjugated. Each 

 liquid of b 1 K l may, therefore, be in equilibrium with a definite 

 liquid of b i K l while both are saturated with solid (NH 4 )«,S0 4 . 



The intersection of the binodal surface with the surface D, namely, 

 the curve b x kjb t represents the solutions of the system L x -f- Tv 2 -j- Li 

 NH 4 S0 4 . With each liquid of bjc % another one of b % k^ may, therefore, 

 be in equilibrium while both are saturated with solid LiNH 4 S0 4 . 



The points of intersection 6, and b 2 of these two curves give the 

 system : L, + L 3 + (NH 4 ) 3 S0 4 -f- Li NH 4 S0 4 , namely two liquids both 

 saturated with ammonium sulphate and lithium ammonium sulphate 

 which may be in equilibrium with each other. 



The points h x and k 2 have a special significance; both are critical 

 liquids which, however, are distinguished from the other critical 

 liquids of the critical curve k L l\ 2 in that they are also saturated with 

 a solid substance: k x is saturated with ammonium sulphate and /., 

 with lithium ammonium sulphate. 



It the temperature is raised the heterogeneous sphere is extended; 



