220 



of the active &-bromo-camphor-7r-sulphonic acid. The tri-ethylene- 

 diamine-cobalti-bromide : 



[Co(Eine) 3 }Br 3 + 3H 2 0, 



was resolved into its optically active components by Werner *) 

 by means of its d-bromo-tartrate, and the same method can be used 

 in the case of the corresponding rhodium-salt. 2 ) The latter, and 

 also the corresponding chromi-salt, may also be separated by the 

 aid of sodium-d-camphor-nitronate 3 ), while potassium-rhodium-oxalate, 

 and the corresponding chromi-sa.lt 4 ), can be split by means of 

 strychnine 5 ). The very strongly rotating components of these salts 

 themselves can in their turn be used for the fission of externally 

 compensated organic compounds; thus Werner and Basyrin 6 ) 

 succeeded in separating the racemic a-x'-dimethyl-succinic acid: 

 COOH.CH(CH 3 ).CH(CH 3 ).COOH, which till then had not been 

 resolved by any other means, into its antipodes by the aid of the 

 optically active tri-ethylenediamine-cobalti-salt. The number of these 

 examples can easily be augmented. A review of fissions made up 

 to 1894 was given by Win t her 7 ), while numerous instances can 

 be found in all larger works on stereochemistry, thus in that of 

 Bischoff-Walden 8 ), that of Werner 9 ), etc. The number of experi- 

 ments in this direction has since increased very rapidly. 



The application of the method is universal, but in every case 

 the difficulty is the choice of the optically active compound suited 

 for the purpose. Everything depends upon the finding of favorable 

 solubility-relations between the newly formed compounds : commonly 

 the greater the difference in solubility is, the better the separation 

 will succeed. Moreover, suitable conditions for crystallisation play an 

 important role in this; often the compounds formed can only be 

 obtained as syrups, or do not form well developed crystals. Every 

 one who has had occasion to make experiments of this kind, knows 



!) A. Werner, Ber. d. d. Chem. Ges., 45, 121, (1911); F. M. Jaeger, Proceed. 

 Kon. Akad. van Wet. Amsterdam, 17, 1271), 1915); Receuil des Trav. Chim. d. 

 Pays-Bas, 38, 171, (1919). 



2 ) A. Werner, Ber. d. d. Chem. Ges., 45, 1228, (1912). 



3 ) A. Werner, ibidem. 



4 ) A. Werner, Ber. d. d. Chem. Ges., 45, '865, (1912). 



5) A. Werner, Ber. d. d. Chem. Ges., 47, 1945, (1914); 45, 3061, (1912). 



6 ) A. Werner and M. Basyrin, Ber. d. d. Chem. Ges., 46, 3229, (1913). 



7) Ch. Winther, Ber. d. d. Chem. Ges., 28, 3000, (1895). 



8) C. A. Bischoff and P. Walden, Handbuch der Slereochemie, (1894). 



9 ) A. Werner, Lehrbuch der Stereochemie, Jena, (1904). 



