( BiÖ ) 



inetliyl aleoliol mixtures saturated with solid salt, whilst mn indicates 

 the solutions of mixtures of ethyl alcohol and methyl alcohol, also 

 saturated with solid salt. 



The quaternary equilibria, namely the solutions of mixtures of 

 water, methyl alcohol and ethyl alcohol saturated with solid salt are 

 I'epresented by the surface wma which we may call the saturation 

 surface of the solid salt Z. 



If we introduce through one of the sides for instance thi'ough 

 \VX a plane such as the plane WZp all points of that plane 

 then represent phases containing the components A and Af in the 

 same |)i-oportion. This plane intersects the saturation surface along the 

 curve iiiq; this, therefore, indicates solutions saturated with solid 

 salt in which the relation between methyl alcohol and ethyl alcohol 

 is constant. 



The points of such a curve are easy to obtain; the two alcohols 

 are first added together so as to yield a mixture represented by p 

 for instance; on adding vai'ying quantities of water we obtain the 

 points of the line [)]V and on saturating these solutions with the 

 salt the points of the curve qir are indicated. 



In this manner ditferent sections of the saturation surface with 

 planes passing through the side \\Z have been obtained. 



In the system, water, methyl alcohol, ethyl alcohol and potassium 

 nitrate perfectly analogous equilibria occur; the saturation surtace 

 for 3(P iu this system has been detei'mined by Miss C. dk Baat. 



In the system ; inati'r, cthi/I alcoliol, ammoniuDi nitrate and silver 

 nitrate the I'elations are somewhat less sini|)le, for at 30° we have 

 two solid couiponents and one douldc salt:, Ag NO3 . NH^ NOg; the 

 equilibria occurring at 30 arc represented in Fig. 2. Whereas Fig. J 

 is a perspective representation of the tetrahedron, Fig. 2 is a pro- 



