TRANSITION OF STEREO-ISOMERS 113 



here on the right, and conversely the mixture of racemate 

 with the respective tartrates (2) and (3) comes here on the 

 left. 



Solubility measurements of the racemate-tartrate mixture 

 gave per 100 molecules of water, expressed in molecules 

 of Kb 2 C 4 O 6 H 4 : 



Te mperature r- Tar fr ate I" Tartrate 



25 

 30 



35 

 40-4 



9.15 

 8-46 

 7-8 

 6-74 



2-8 

 4-11 

 5-ia 

 6.74 



r + l 



0-531 



0-346 



0-208 



o 



Fig. 21 is the projection of a model that represents these 

 data. T is the axis of temperature ; dextro-tartrate is 



Fig. 21. 



measured upwards, laevo-tartrate downwards, so that R r/ B 

 represents the data just given, while AB and BC correspond 

 to those that are also drawn on Fig. 20, and refer respec- 



1 The way in which the relative excess of one antipode approaches zero 

 is very characteristic of the transition temperature. 



