274 



active salts exhibit, it was now found l ) that, although in some 

 cases enantiomorphism really manifested itself, this was, however, 

 reduced in several instances to an undetectably feeble degree. 



The d- and l-bromides : {Co(Eine) 3 } Br 3 -f- 2# 2 0, did not show 

 under any circumstances of crystallisation, the slightest indication 

 of hemihedrism; while in the case of the iodides: [Co(Eine) 3 }I 3 

 -f- Hf>, and of the rhodanides: [Co(Eine) 3 }(SCN) 3 , even the 

 corrosion-figures obtained were in full accordance \vith holohedral 

 symmetry, instead of being a proof of hemihedrism. If enantio- 

 morphism be present here, it is evidently manifested to such an 

 extremely slight degree, that it is not detectable by any crystallo- 

 graphical method at hand. 



From this it becomes evident, that in this case there is surely 

 no rational proportion present between the enormous optical 

 activity of the molecules on the one hand, and the undetectable 

 hemihedrism on the other. The cause of this can only be the identity 

 of the dissymmetrically arranged substitutes: C 2 H^(NH 2 ) 2 . 



It becomes highly probable, therefore, that, while the optical 

 activity appears to be chiefly caused by the non-superposable atomic 

 arrangement as such, the enantiomorphism of the crystalline forms 

 seems to be more especially governed by the chemical contrast between 

 the substitutes placed round the plurivalent central-atom. 



The occurrence of hemihedrism 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, just as 

 the non-superposable configuration itself is for the rotatory power 

 of the molecule. 



In the case of the potassium-rhodium-tri-o%alales\ [R/io(C ? 4 ) 3 }K 3 , 

 which represent a similar case of symmetrical arrangement, the 

 enantiomorphism of both antipodes is certainly present; in that 

 of the corresponding cobalti-, and indium-salts also 2 ). However, 

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

 active compounds belong to a much higher symmetrical system 



1 ) F. M. Jaeger, Proceed. Kon. Akad. v. Wet. Amsterdam, Vol. 18, 52, 56, 

 63, 65, 67, (1915); Zeits. f. Kryst. u. Miner., 55, 209, (1915) ; Chemisch Weekblad, 

 14, 718727, (1917); Receuil des Trav. d. Chim. d. Pays-Bas, 38, 171, (1919). 



2 ) F. M. jaeger, Proceed. Kon. Akad. v. Wet. Amsterdam, Vol. 20, 263, (1917) ; 

 21, 203, 698, (1918); Chem. Weekblad, 14, 727, (1917); Receuil des Trav. d. Chim. 

 d. Pays-Bas, 38, 171, (1919); Revue generate des Sciences, 3.0, 298, (1919). 



