261 



appears to be chiefly caused by the non-superposable atomic 

 as such, the enantiomorphism of the crystalline forms 

 wins to be more especially governed by the chemical contrast between 

 the substitutes placed round the plurivalent central-atom. 



1 la- occurrence of In mihedrism in some cases of this kind 

 proves, however, that the chemical contrasts, between the sub- 

 stitutes mentioned cannot be exclusively the cause of it. But it 

 seems highly probable that it is the preponderant factor for it, 



Fig. 1 68. 

 Racemic and Optically active crystals of Potassium- Rhodium-Oxalale. 



just as the non-superposable configuration itself is for the rotatory 

 power of the molecule. 



In the case of the potassium-rhodium-tri-oxalates : {Rho(C t O t ) 3 }K 9 , 

 which represent a similar case of symmetrical arrangement, the 

 enantiomorphism of both antipodes is certainly present. *) However 

 here there is also a somewhat abnormal case, in so far as the 

 optically active compounds belong to a higher symmetrical system 

 (trigonal), than the racemic compound (triclinic). The symmetry 

 of the active components is Z) 3 (fig. 268), while that of the racemu- 

 compound is /, the ternary and the three binary axes of the 

 dextro- and laevogyrate components being changed into a single 



') F. M. Jaeger, Proceed. Kon. Akad. v. Wet. Amsterdam, Vol. 19. (1917); 

 Chem. Weekblad, 14. 727. (1917). 



