ARTICLES 



259 



The conception of the octahedral structure of these com- 

 plex compounds leads to many further conclusions, some of 

 the most far-reaching of which have lately received at Werner's 

 hands a most remarkable experimental verification. 



For example, in the case of those cobaltic compounds of the 

 constitution [(N0 2 ) 2 Co en 2 )X which have already been referred 

 to two series are known : 



\'4m> 



Trans (Croceo-series). 



Cis (Flavo-series). 



If one of the ethylene diamine molecules in these com- 

 pounds could be replaced by a similar but unsymmetrically 

 constituted diamine, as, for example, propylene diamine 

 NH a *CHo*CH (CH 3 )*NH 2 ( = pn) trans and cis modifications 

 should again be possible, whilst the latter should be capable of 

 existing in two structurally different forms in which the methyl 

 group is near to or further removed from the plane in which 

 the two N0 2 groups are situated. 



4*^-1 



CH^-C-H 



These predictions have been put to the test of experiment and 

 confirmed; croceo and flavo salts have been obtained, and the 

 latter have been found to exist in two forms, one termed the a 

 or prismatic, crystallising in prisms, the second called the £ or 

 needle-shaped, crystallising in needles. 



Again, as propylene diamine contains an asymmetric car- 



