242 



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

 ponding chromi-salt. 



From the following examples *) : 



[Cr(Eine) 3 }I 3 , M D =+m; [Cr(Eine) 3 }(SCN) 3 , [71^= +335. 

 [Co(Eine) 3 }I 3 , M D =+W72; {Co(Eine) 3 }(SCN) 3 , [M] D =+78\. 

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

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

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

 of rhodium is about twice that of chromium. 



The author however canwo^ 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 tri-ethylene- 

 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 2 ), 

 has concluded that the laevogyrate rhodium-salts and the dextro- 

 gyrate cobalti-salts which are set free from the less soluble halogeno-d- 

 tartrates, must possess the same configuration in space. Therefore, 

 according to this author, if in the tri-ethylenediamine-complex of 

 the cobalti-salts the central cobalt-atom be replaced by the rhodium- 

 atom, not only the size of the specific rotation would be altered, 

 but even its direction would be reversed. However Werner does not 

 give any plausible argument to support his starting-point regarding 

 a direct connection between the configuration of the molecules and 

 their solubility. Moreover this view seems to be quite fortuitous, 

 as the solubility of compounds is so highly complicated a constitutive 

 property of matter, that even where rules for homologous compounds 

 apparently universally valid seem to be established, the most unex- 

 pected and surprising facts often appear to make them illusory after- 

 wards. The crystal- form of the substances, on the contrary, is a property 



1) A. Werner, Ber. d. d. Chem. Ges. 45. 1234, 1236. (1912); F. M. Jaeger, 

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



2) 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 /aezwgyratory 7?Ao-salts 

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



