( 31'^ ) 



Pseudo-raccmk mixed cnjdals. As I dcuionstrated on a former 

 occasion, mixed crystals must be considered as one solid phase. For 

 mixed crystals formed of optical antipodes, if they exist, it will per- 

 haps be possible to appear in every proportion. In such a case we 

 should only get one solubility-curve in fig. 1, connecting the points << 

 and h and being symmetrical again. 



If at lower temperatures, a racemic combination should appear, 

 the continued mixing-series would be broken by it. The sketch of 

 the solubility curves would consequently be altered in so far that 

 the lines KA and CA would pass into one continnous curve. The 

 evaporation phenomena would equally be altered. 



11. Melting points. The opinion exists 

 that a higher melting point is a proof of a 

 racemic combination when compared with the 

 melting point of the antipodes. Uncertainty 

 exists when the melting point of the inactive 

 substance is equally high or lower. 



Here too,' it is only the study of the 

 melting- and congealingcurves along their 

 entire lengths, that can give us sufficient 

 certainty. 



If no combination, nor mixed crystals exist, 

 fig. 2 must give the groundplan for the 

 congelation. The mixing proportions of L 

 and D are indicated on the horizontal axis, 

 B the temperature on the vertical. A and B 

 are the melting points of L and I). AC is 

 K^ the congealing-line for liquids depositing L, 

 BC for such as deposit D. Every mixture 

 congeals at last in C to an inactive conglo- 

 merate of L and D. If on the other hand 

 there is a racemic combination, two types 

 are possible, represented by fig. 3 and 4. 

 In these C is the melting point of the com- 

 bination, which is higher or lower than the 

 melting points A and B. Independent of 

 this fact, the congelation now leads to three 

 curves, the one in the middle representing 

 the case that the combination is deposited. 

 It has two branches. 



If, to end with, there is a continual mixing- 

 series, there will be but one congealing 

 curve. But the latter need not be, inarepre- 



