231 



neously mixed to some extent with their products of dissociation 

 The racemic compounds would, in his opinion, never crystallise 

 in forms differing from their mirror-images. And finally he draws 

 attention to the fact that, in contradiction to Gernez' views 1 ), 

 iriboluminescence 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 pheno- 

 menon of triboluminescence suddenly disappears. Further investiga- 

 tion of these relations seems to be highly desirable, and certainly 

 his conclusions cannot be adopted as being of general validity. 



As further examples of this kind, Kipping and Pope mention 

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

 bromides 2 ) ; carvoxime 3 ) ; dipentene-tetrabromide 4 ) ; u-bromo-camphoric- 

 anhydride 5 ); carvon-tribromide 6 ), etc. Among Minguin's camphor- 

 derivatives 7 ) there are certainly also to be found some interesting 

 examples of this kind. 



If Bruni's 8 ) suspicion is correct, that the so-called "double-salt" 

 of d-ammonium-tartrate and l-ammonium-malate , described by Pas- 

 teur 9 ), is really a mixed-crystal, we should have here an object 

 intermediate between a pseudo-racemic mixed-crystal and a 

 partially-racemic compound, as defined by Fischer 10 ), who draws 

 attention to the fact that these salts are only antipodes with 

 respect to one half of their molecule. The corresponding d-tartaric 

 acid and l-malic acid themselves do not form such a double 

 compound or pseudo-racemic mixture. Fischer proposes to give 

 in that case a special name to the phenomenon stated above, and 



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

 gajeff, Ber. d. d. Chem. Ges., 34, 1820, (1901); A. Imhof, Phys. Zeits., 18,78; 

 374, (-1917). 



2 ) F. S. Kipping and W. J. Pope, Journ. Chem. Soc. London, 63, 565, (1893). 

 67, 359, (1895). 



3 ) P. Beyer, Zeits. f. Kryst., 18, 198, (1890); J. H. Adriani, loco cit. 



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



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

 203, 205, (1896). 



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



7) J. Minguin, loco cit. 



8 ) G. Bruni, in: W. Meyerhoffer, Gleichgewichte der Stereomeren, (1906), p. 62. 



9) L. Pasteur, Jahresberichte, (1853), p. 417. 



10) E. Fischer, Ber. d. d. Chem. Ges., 40, 944, (1907). 



