2 6o SCIENCE PROGRESS 



bon atom and consequently can be obtained in optically active 

 d and 1 modifications, if in the preparation of the compounds 



["(NO,), Co e JX the oppositely active bases are employed, the 



theory predicts the possible existence of numerous optical 

 isomerides. 



For example, the trans isomeride (croceo salt) of the for- 

 mula \ / vr^ a Co ' |X should exist in three forms, 

 L6, NO a pnJ 



the d-trans compound j th(j racemic tmns c und 



the 1-trans compound J 



whilst eight optically active modifications of the two series of 



cis-isomerides (flavo salts) of the constitution ["^' AT^ a Co en |X 

 x L4. N0 3 pnJ 



are theoretically possible due to different spatial positions of 



the methyl group in complexes containing the two connecting 



diamine chains differently orientated as previously described, 



namely : 



In the a, or prismatic series : 



d. propylene diamines ' c ° , 

 v |L cobalt 



1. propylene diamine/?' "J 1 * 1 * 



(1. cobalt 



In the fi, or needle series : 



d. propylene diamine/?' c ° b * h 



[1. cobalt 



1 i j- fd. cobalt 



1. propylene diamine^, , , 

 r ^ J [I. cobalt 



These eight optically active compounds should be able to 

 combine in different ways to give eight partially racemic and 

 two completely racemic compounds which may be summarised 

 as follows : 



Four compounds which are racemic with respect to cobalt. 



In the a or prismatic series : 



'd. propylene diamine -d. cobalt + d. propylene diamine 



-1. cobalt. 

 1. propylene diamine -d. cobalt -f- 1. propylene diamine 

 -1. cobalt. 



