214 



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

 also the corresponding chromi-sa.lt, may be separated also by the 

 aid of sodium-d-camphor-nitronate 2 ), while potassium-rhodium-oxalate , 

 and the corresponding chromi-sa.lt 3 ), can be split by means of 

 strychnine*). 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 5 ) 

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

 COOH.CH(CHz).CH(CH z ).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-sa\t. The number of these 

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

 to 1894 was given by Wintrier 6 ), while numerous instances can 

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

 Bischof f-Walden 7 ), that of Werner 8 ), etc. Since the number of 

 experiments in this direction has increased very rapidly. 



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

 the difficulty is the choosing 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 fission 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 

 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 



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



2 ) A. Werner, ibidem. 



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



4) A. Werner, Ber. d. d. Chem. Ges. 47. 1954. (1914); 45. 3061. (1912). 

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



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



V) C. A. Bischoff and P. Walden, Handbuch der Stereochemie, (1894). 



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



