222 



the solubility-curve TS for the mixture no longer coincides with 

 OA, because of the difference in solubility of the dextro-, and lae- 

 vogyratory component. QT might even lie wholly to the right of 

 OA, and in that case the temperature-range MT in which no solu- 

 tions of the pure racemoid can exist, will become yet greater, the 

 racemoid being continually decomposed by gradual precipitation 

 of the laevogyratory salt, until at the transition-temperature corres- 

 ponding to T, the fission is finally completed. 



Of course, the solution which corresponds to this transition-tem- 

 perature, does in general not necessarily contain equal quantities 

 of the dextro- and laevogyratory compounds; this can only be 

 the case approximately, when the difference of their solubilities 

 at the temperature under consideration is very slight. 



If the splitting-up of the partial racemate does not occur, or cannot 

 be produced in some way, partial racemism may, therefore, also be 

 an obstacle for the successful fission of a racemoid by this method. 

 Many cases of partial racemism have since been observed: strych- 

 nine-racemate, tetrahydro-papaverine-d-tartrate l ), l-menthyl-mandelic 

 ether 2 ), etc. 



Ladenburg 3 ) found for $-pipecoline-bitartrate a partial racemism 

 at higher temperatures, while a fission occurred at lower tempera- 

 tures. For bmcine-biracemate 4 ) a transition-temperature of 50 C. 

 was found, below which the partial racemate can exist, while at 

 higher temperatures fission takes place. Levi-Malvano and 

 Mannino found partial racemism with some santonine-salts 5 ), 

 while Windaus und Resau 6 ) met with a partial racemic com- 

 pound in the case of (3-cholestanol and pseudo-coprosterol. The 

 number of such cases increases from year to year. 



10. Fission of Racemoids by the aid of living Organisms. 



The third method of fission also proposed by L. Pasteur 7 ), 



!) W. J. Pope and S. J. Peachy, Zeits. f. Kryst. u. Min., 31, 11, (1900); 

 Journ. Chem. Soc. London, 73, 902, (1898). 



2 ) A. Findlay and E. M. Hickmans, Journ. Chem. Soc. London, 91, 909, 

 (1907). 



3 ) A. Ladenburg, Ber. d. d. Chem. Ges., 27, 75, (1884). 



4 ) A. Ladenburg, Ber. d. d. Chem. Ges., 40, 2279, (1907). 



5 ) M. Levi-Malvano and A. Mannino, Atti Rend. Acad. Lincei Roma, (5), 

 18, //, 144, (1909). 



6) A. Windaus and C. Resau, Ber. d. d. Chem. Ges., 48, 861, (1915). 



7) L. Pasteur, Compt. rend, de 1'Acad. d. Sc. Paris, 32, 110, (1851); 36, 26, 

 (1853); 37, 110, 162, (1853); 51, 298, (1860). 



