259 



In the preceding paragraphs we were able to demonstrate : 



1. that in analogously built, opÜQa,\\y-i7iactive complex salts of 

 trivalent cobalt and trivalent rhodium, the two metals will replace 

 each other strictly isomorphously. This fact is in full agreement with 

 what can be expected because of the place these elements occupy 

 in the eighth group of the periodical system. 



2. that in analogouslj' built, optically-rtc^/ï't; complex salts of 

 trivalent rhodium and cobalt, this isomorphous mutual substitution 

 of the central atoms remains. This specific property of the metal- 

 atoms obviously appears therefore not influenced by tlie special 

 dissymmetry of the molecules, in which they are present. 



Now we will suppose that the dextro-^yrsLiQ, and just in the 

 same way the laevo-^yraXe, tri-ethylenediamine-cobalti-chloride is trans- 

 formed into the corresponding chloro-tartrates by means of silver- 

 d-tartrate. Of course the crystal-forms of both these compounds 

 d'd and I'd, being no longer each other's mirror-images, will be 

 different from each other. For among all properties of chemical 

 molecules none is certainly so closely connected with their molecular 

 configuration, as the crystal-form is. With respect to the identical 

 d-tartrate-Ydidi\Q.3i\ in the two compounds, it is therefore the two special 

 configuration of the d'-, resp. r-tri-ethyienediamine-coba/ti-radicsds, 

 which determines the differences of crystal-form in the case of the 

 two chloro-d-tartrates just mentioned. 



If now, while completely preserving the existent stereometrical 

 arrangement of the radicals round the central Cb-atom, we think 

 this last simply replaced by the Rho-diiom which, according to what 

 is mentioned sub 2") in the above, will replace it in the way of 

 a perfect isomorphous element, — then it will be evident that the 

 two complex /?Ao -com pounds thus obtained will be perfectly iso- 

 morphous with the two corresponding 6t>-salts just mentioned, and 

 more particularly each of them with that Cb-salt which possesses 

 an analogous configuration of its radicals in space. This conclusion 

 is compelling, quite independent of the other question concerning 

 the special influence which this substitution eventually may have 

 on the size and even on the sense of the optical rotation of the 

 original molecule, or on its solubility. The chloro-d-tartrates of Co- 

 an /?Ao-complexes with corresponding configuration therefore will 

 exhibit perfectly isomorphous crystal-forms, independently of their 

 specific optical properties or of the differences in their solubilities. 



Also the number of molecules of water of crystallisation in the two 

 isomorphous crystal-species will be exactly the same. 



Experience now teaches us that the less soluble tri-ethylene- 



