210 



The isotherms a'6' are in the same way solubility-curves for 

 another temperature t' situated below (fig. 759) or above (fig. 160) 

 the transition-temperature under atmospheric pressure. At Q and P 

 they will meet the solubility-isotherm PrQ for the racemate, the 

 solubility of which is of course influenced by an excess of the right- or 

 left-handed component. 



The point r is the optically inactive solution which is saturated with 

 .respect to the racemoid, the point of intersection x represents the 

 more concentrated, metastable, inactive solution which would be in 



equilibrium with a mixture of 

 the components at the same 

 temperature, if this equilibrium 

 could be realised. This meta- 

 stable solution would be super- 

 saturated with respect to the 

 racemic substance. 



At the transition-tempera- 

 ture itself, the solution T may 

 exist in stable equilibrium with 

 the racemic compound, or with 

 the right- and lefthanded com- 

 ponents. Thus on TQ are all 

 solutions which, at increasing 

 (or decreasing) temperatures, are 



simultaneously saturated with respect to the racemate + excess of the 

 left component, and on PT are all solutions which behave in the 

 same way with respect to the racemate -f- excess of the right com- 

 ponent. If, perpendicular to the plane of the figure, a third axis OZ 

 be taken as temperature-axis, a complete survey of these relations 

 can be given in a tridimensional model. 



The whole behaviour is completely analogous to that of ordinary 

 double-salts 1 ), the only difference here being this, that the whole 

 figure is completely symmetrical with respect to the line OA bisecting 

 the angle between the axes OX and OY, in consequence of the iden- 

 tical chemical and scalar physical properties of both optically active 

 components. 



As to the question whether racemic compounds be really present 

 in the liquid state, it may be briefly remarked here, that there is 



x ) H. W. Bakhuis Roozeboom, Zeits. f. phys. Chemie, 2, 513, (1888); 10, 

 145, (1892); F. A. H. Schreinemakers, ibidem, 9, 57, (1892). 



