230 



pseudo-racemic mixed-crystals, the pseudo-racemic mixtures have 

 also been the subject of some investigations l ) ; however, it is also 

 very necessary in this case, that more extended and systematic 

 researches be made to further our rudimentary knowledge in many 

 directions. 



Kipping and Pope 2 ) described the irans-7r-camphanic acid as a 

 first example of such pseudo-racemic mixtures; the active and inac- 

 tive substances have very similar crystal- forms .and appearance: 



Active: Monoclinic; a : b : c = 1,9110 : 1 : 1,4627; /3 = 695'. 

 Inactive: Monoclinic; a : b : c ='1,8105 : 1 : 1,4502; /3 = 674r. 



The same was the case with the active and inactive trans-campho- 

 tricarboxylic-anhydrides. The investigators mentioned come to the 

 conclusion, that the crystals of the inactive substance are not homo- 

 geneous, but merely complicated intercalations of crystals of the 

 (f-and /-components; the bad and multiple reflexes of the light on 

 some faces, observed during the measurements, their striation, 

 etc., remind us very much of similar peculiarities, met with in 

 mixed-crystals and in crystalline aggregations as, for instance, are 

 found in some amethyst-crystals. The angular values of inactive and 

 active crystals are very analogous; small, but perfectly distinct 

 differences are, however, actually present, which the authors at- 

 tribute to the disturbing effect of the intercalation. 



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

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

 crystals between strictly isomorphous salts. 



Ostromisslensky 3 ) 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 ^interrupted 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- 



!) J. H. Adrian!, Akad. Proefschrift, Amsterdam, (1900) ; Zeits. f. phys. Chemie, 

 33. 453. (1900); 36. 168. (1901); Proceed. Kon. Akad. v. Wet. Amsterdam 9. 483. 

 (1900); J. Minguin and E. G. de Bollemont, Compt. rend, de 1'Acad. d. 

 Sciences Paris, 132, 1573, (1901); J. Minguin, Bull. d. 1. Soc. Chim., (3), 27, 888, 

 (1902); Compt. rend., 124, 86, (1897). 



2 ) F. S. Kipping and W. J. Pope, Journ. Chem. Soc. London, 69, 931, 

 (1896); etc. 



3 ) I. Ostromisslensky, Journ. d. russ. phys. chem. Ges. St. Petersburg, 

 42, 102, 606, (1910). 



