223 



Ir.-tlv distinct differences however are actually present, which the 

 author* mentioned attribute to the disturbing effect of the int. i- 

 calation. 



In so far such pseudo-racemic mixtures appear closer related to 

 so-called layer-crystals than to the true homogeneous mixed- 

 crystals between strictly isomorphous salts. 



Ostromisslensky 1 ) considers the formation of pseudo-racemic 

 mixtures from the d~ and /- components as a transformation of the 

 antipodes into a second, dimorphic and holohedral modification. 

 Pseudo-racemic mixed-crystals can only form an wninterrupted series 

 of mixtures; however Ostromisslensky thinks it possible that 

 the active antipodes eventually form solid solutions with a racemic 

 compound, in the same way as some compounds can be homoge- 

 neously mixed to some extent with their products of dissociation. 

 The racemic compounds would never crystallise in forms differing 

 from their mirror-images. And finally he draws attention to the 

 fact that in contradiction to Gernez' views 2 ), triboluminescence 

 may be used as a criterion to discriminate between an externally 

 compensated mixture and a true racemic compound. If the active 

 form shows triboluminescence, the racemic compound does not; 

 at the transition-temperature of a mixture, the phenomenon of 

 triboluminescence suddenly disappears. Further investigation of 

 these relations seems to be highly desirable. 



As further examples of this kind, Kipping and Pope mention 

 the d- and l-camphorsulphonic-chlorides , and the corresponding 

 bromides 3 ) ; carvoxime *) ; dipentene-tetrabromide 6 ) ; u-bromo-camphoric- 

 anhydride 6 ); carvon-tribromide 1 ), etc. Among Minguin's camphor- 

 derivatives 8 ) there are certainly some beautiful examples of this 

 kind too. 



1) I. Ostromisslensky, Joum. d. russ. phys. chem. Ges. St. Petersburg 

 42. 102, 606. (1910). 



2) D. Gernez, Compt. rend, de 1'Acad. d. Sc. Paris 147. 11. (1908); L. Tschu- 

 gajeff, Ber. d. d. Chem. Ges. 84. 1820. (1901). 



8) F. S. Kipping and W. J. Pope, Journ. Chem. Soc. London. 68. 565. (1893); 

 67. 359. (1895). 



) P. Beyer, Zeits. f. Kryst. 18. 298. (1890); J. H. Adriani, loco cit. 

 6) C. Hintze, Ann. der Chemie 227. 278. (1885). 



6) O. Aschan, Acta Soc. Scient. Fenn. 21. (V). 193. (1896); F. J. Wiik, ibid. 

 203, 205. (1896). 



7) Th. Liebisch, Ann. d. Chemie, 286. 142. (1895). 



8) J. Minguin, loco cit. 



