OF ARTS AND SCIENCES. 



or to RcX.^Y^Z.,. Now the salts of either of these types may he equally 

 well referred to either of the structural formulas given ahove. To 

 which of them are we to refer salts of roseocobalt, and to which salts of 

 purpureocobalt ? 



Blomstrand gets over the diiliculty in part by the short and easy 

 method of declaring that chloride of roseocobalt is only the hy- 

 drate of chloride of purpureocobalt. I think I have shown con- 

 clusively that this view is wholly untenable. But, even if we admit its 

 correctness, to wliich of the four structural formulas shall we assign 

 chloride of purpureocobalt alone, since all four explain its relations to 

 other chlorides, and its products of replacement equally well ? 



The case is the same with the other cobaltamines, though in these 

 we have no isomerisms to explain, in the present state of our 

 knowledge at least. The dodecamin and octamin series exhibit the 

 two types LcX,., OcX,., and LcX^Yg, OcX^Y^, with perfect distinctness ; 

 but in addition we have in the case of the dodecamin series the type, 

 LcXgYc,, as, for instance, in the phosphate described by Braun, 

 Co.,(NH3),2(P20^)-f-80H,„ and perhaps also in the pyrophosphate 

 Co.,(NH3),2P40j..-[-60H2, though this salt may be referred to the type, 

 LcX,., if we consider (P.jOj.,) as a hexatomic complex. Luteocobalt 

 may therefore be saturated, if I may so speak, by ones as in LcCl^, 

 by twos as in Lc(S04)^l2, and by tlirees as in Lc(P04)2. It would 

 seem as if we in this manner arrive most naturally at the structural 

 formulas for the dodecamin series, — 



Co., i 



a — a — CI 

 a— a— CI 

 a— a— CI 

 a — a — CI 



a — a — CI 

 a — a — CI 



Co, 



a — a — O 



a- 

 a- 



a- 

 a- 



-a— O 

 -a— I 

 -a— I 

 -a— O 



a — a — O 



>S0, 



>so., 



a— a— O ) 

 a— a— O I PO 

 ^; a — a — O ) 



^^^ Kx-a-OJ 



I a— a— O V PO 

 [ a — a — O ) 



in which the six ammonia groups have equal weights or qualitative 

 values, so that the six units of affinity of C02 must also be of the same 

 kind and the same inten ity. But, if we examine the list of salts of 

 roseocobalt which I have given, we find that Krok has described a 

 salt with the f /rmula, — 



Co,(NH3),,(N03)3Cl3+3HgCl2; 



