221 



the disillusioning obstacles often presented to him and the serious 

 difficulties to be overcome. 



9. Attention must be drawn to another difficulty which may 

 crop up, namely, that the optically active component often does not 

 combine directly with each of the two active components contained 

 in the racemoid separately, but with the whole racemic compound 

 as such, which combination then above or below a certain transition- 

 temperature may be changed into a mixture of the two different 

 compounds which are contained in it. The behaviour of such a 

 partial racemic compound, 

 as it is called, is then quite 

 analogous to that of a race- 

 mic compound above or 

 below its transition-tempe- 

 rature, except that the typical 

 symmetry of the solubility- 

 relations is lost, because the 

 pseudo-racemic compound no 

 longer splits up into com- 

 ponents which are mirror- 

 images of each other. 



The first example of this 

 kind was found by Laden- Fig. 161. 



burg ^ in the case of strych- 



nine-racemate, and of the salt formed from quinine and methylsuccinic 

 acid. The first substance appears at 30 C. to have a (maximum) 

 transition-temperature. Above 30 C., therefore, it is split up into 

 strychnine-d-tartrate and strychmne-l-tartrate. 



The solubility-relations existing in such cases were first fully 

 understood and explained by Bakhuis R ooze boom 2 ). The sym- 

 metry of our former figures is of course now lost (fig. 161), while 



J ) A. Ladenburg and collaborators: Ber. d. d. Chem. Ges., 27, 75, (1884); 

 31, 524, 937, 1969, (1898); 32, 50, (1899); 36, 1649, (1903); 40, 2279, (1907) ; 

 41, 966, (1908); Ann. der Chemie, 364, 227, (1909); E. Fischer, Ber. d. d. Chem. 

 Ges., 27, 3225, (1894). F. S. Kipping, Journ. Chem. Soc. London, 95,408, 

 (1909); M. Levi-Malvano and A. Mannino, Atti Rend. Acad. Lincei Roma, 

 (5), 18, //, 144, (1909); A. Windaus and C. Resau, Ber. d. d. Chem. Ges., 

 48, 861, (1915); F. W. Kiister, Ber. d. d. Chem. Ges., 31, 1847, (1898); A, 

 Findlay and E. M. Hickmans, Journ. Chem. Soc. London, 91, 905, (1907); 95, 

 1386, (1909). H. Dutilh, Proceed. Kon. Acad. v. Wet. Amsterdam, 12, 393, (1910). 



2 ) H. W. Bakhuis Roozeboom, Zeits. f. phys. Chemie, 28, 502, (1899). 



