251 



however, to any chemical contrast between the groups round the 

 plurivalent atom 1 ). 



That the special nature of the central metal-atom also takes a 

 predominant part in this, can be seen on comparing the magnitude 

 of the molecular rotation of some analogously composed salts of 

 the metals Cr and Co: 



Cr 



Co 



(Eine) 



Br, (M) D = ca. 1100; (M) c = ca. 545 

 Br, (M) D = ca. 2525; (M) c = ca. 906, 



(Eine\ 



the rotation of the cobalti-salt being about double that of the corres- 

 ponding chromi-sdilt. 



From the following examples 2 ) : 



[Cr(Eine) 9 }I M D =+37S; {Cr(Eine) 3 } (SCN) 3 , [^=+335. 

 [Co(Eine) 8 }I 9 , M D = + \072; {Co(Eine) 3 } (SCN) 9 , [M] J> =+781. 

 {Rho(Eine) 3 } 7 3 , M D = +329 ; {Rho(Eine) 3 } (SCN) 3 , [M] D = +335. 

 the remarkable fact is best elucidated that the Rho-sailts exhibit 

 about the same rotation as the CV-salts, although the atomic weight 

 of rhodium is about twice that of chromium. 



The author, however, cannot agree with the Swiss investigator 

 in the reasonings by which he thinks to have proved that the algebraic 

 sign of the rotation in the case of the derivatives of the triethylene- 

 diamine-rhodium-ion is also the opposite to that of the rotation 

 shown by the cobalti-salts of analogous stereometrical configuration. 



Werner, (loco cit. p. 1229) going on the supposition that salts 

 derived from optically active ions of analogous constitution will 

 combine with the same optically active substance to form compounds 

 which will always show a relativity comparable degree of solubility 3 ), 



1 ) Cf.: W. J. Pope, Presid. Address to the Chem. Section, Brit. Assoc. Rep. 

 (1914): "It must however be insisted, that the observed optical activity is the 

 result of the enantiomorphism of the molecular configuration ; the asymmetry 

 of a particular atom is not to be regarded as the cause of the optical activity, but 

 merely as a convenient geometrical sign of molecular enantiomorphism." 



2 ) A. Werner, Ber. d. d. Chem. Ges., 45, 2134, 1236, (1912); F. M. Jaeger, 

 Proceed. Kon. Akad. v. Wet., 17, 18, 19, 20, and 21 ; Chem. Weekbl., 14, 718, (1917) ; 

 Receuil des Trav. d. Chim. d. Pays-Bas, 38, 171, (1919); Revue generate des 

 Sciences, 30, 298, (1919). 



3 ) As Werner, Ber. d. d. Chem. Ges., 45, 1229, (1912), first suggested, those 

 antipodes which combine with the same optically active acid or base into 

 the less soluble compound, should always be those of corresponding stereometrical 

 configuration. Therefore, according to this author, the laevo gyratory Rho-sa\ts 

 should correspond to the dextrogyratory Co-salts, and vice versa. 



