254 



§ 11. Racemic Tki-ethylenediamine-Rhodiüm-Nitrate. 



\Rho{Eine\\{NO,\. 



This compound is always obtained, when a solution of the racemic 

 chloride is mixed with a solution of AgNO^. It crystallises from 

 an aqueous solution in splendid, colourless, and distinctly hemimor- 

 phic crystals, showing a strongly variable aspect, and often distorted 

 in a most particulai- way. Some of the forms most often met with 

 are reproduced in fig. 8 a, b, and c. For the purpose of immediate 

 comparison with the corresponding cobalti-saU, which is completely 

 isomorphous with it, the heteropolar binary axis of the crystals is 

 also in this case adopted as (^if-axis. 



To the well-developed pyramid o, which never fails and always 

 gives good reflexes, the symbol |111| has been attributed, so that 

 the ratio c : h is now exactly half the corresponding ratio of the 

 cobaki-ssilt studied previously: there the symbol |il2| was given to 

 the form o. 



a h c 



Fig. 8. 

 Racemic Tri-cthylenediamine-Rhodium-Nitrate. 



Rhombic- pyramidal. 

 a:b:c = 0,7874 : 1 : 0,5606. 

 Forms observed : a = \100\, well-developed, occasionally predo- 

 minant and always very lustrous; a' = \W0\, mostly absent or ex- 

 tremely narrow, sometimes, however, very large and reflecting 

 perfectly; o = {ill], large and lustrous; m = \Ï20\, if present large 

 and lustrous, but occasionally absent; c==|001|, w^ell-developed and 

 giving very sharp reflexes; wz=|lll|, never failing, but always 

 much smaller than o ; q=::\011\, occasionally absent, in most cases, 

 however, large and lustrous; s ^ \021], much narrower than q, but 

 giving good images; r = |20.01j, small and dull, ordinarily absent; 

 b = jOlOj, always sharply reflecting, and sometimes equally large 

 as q and c. but occasionally much smaller or totally absent; 

 ^; = |120|, extremely small, only rarely present. 



