256 



small but well reflecting; /9 = |120|, much smaller than m, and 

 often totally absent. The shape of the crystals is that of plates 

 parallel to {lOOj, or to two pai*allel faces of m. They are completely 

 isomorphous with those of the cobalti-?>&\i. 



Fig. 9. 

 Laevogyrate Tri ethylenediamine-Rhodium-Nitrate. 



Angles: Observed: 



a: m = (100): (110)=* 40O50' 

 a: = (100): (111)=* 59 5 

 a: r = (100): (101)= 55 1 

 o: r = (iri):(101)= 26 13 

 m: /) = (110):(120)= 19 11 

 o:m = (111): (110)= 84 15 

 o :m = (ni):(lïb)= 47 15 

 o: o =(in):(lTr)= 52 46 

 o:p= (111) : (120) = 82 47 

 a:/)= (100):(120)= 5937 



Calculated : 



55° Ve' 

 26 2IV3 

 19 7 

 84 21 

 47 121/2 

 52 421/3 

 82 421/2 

 59 57 



No distinct cleavability could be found. 



The plane of the optical axes is |010j; in the corner of the image, 

 one optical axis is visible under the microscope, when a plate parallel 

 to m is used. 



^ 13. 



In the accompanying figure 10 the dispersion-curves of both the 

 last mentioned salts have been reproduced. Their shape is absolutely 

 different from that of the corresponding curves of the optically- 

 active cobalii-Qdk\i^, 



