296 



Observed: Calculated: 



o-.q -=021) : (011)= 29 13 29 12 



m:'^' =(110) : (121)= 32 14 32 20 



m:ri=(210) : (101)= 65 20 65 17 



m:r2'=(110) : (101)= 67 12 67 ISVg 



r, .q =(101) : (011)= 51 16 .51 6 



r^.q =(]01) : (011)= 52 3 52 9 



m:9 =(110) : (0U)= 64 38 64 43 



m':(? =(110) : (011)= 60 31 60 38 



'"-.q =(121) : (011)= 27 57 28 18 



Perfectly cleavable parallel to m. 



The crystals are feebly dichroitic: on a yellow-orange for vibra- 

 tions in the direction of the c-axis? and for those perpendicular to 

 them : red-orange. On m is the angle of extinction about 28° with 

 respect to the vertical axis. 



^ 5. TRANS-DlAMINO-DIETHYLENEDIAMINE- 

 COBALTI-IODIDE. 



Co 



{NH,\ 



A- 



{Ei?ie), 



Small, often badly developed crystals "h 

 with a dark red-brown colour; their 

 aspect is that of hexagonal plates (tig. 4). 



Rhombic-bipyramida I. 

 a: 6: = 1,2449:1: 1,2842. 



Forms observed : a = [100], distinctly 

 predominant and very lustrous ; o = [111], 

 and m = [120], well-developed and giving 

 sharp mirror-images. 



Angles 



a: o =(100) 

 a-.m =(100) 

 o:o =(111) 

 m:m = (120) 

 m -.0 =(120) 

 0.0 =(111) 



Observed 

 (111)=* 57°58' 

 (120)=* 68 7 

 (llT)= 64 12 

 Ti20) = 43 46 

 (111)= 35 46 

 (lTl)= 83 58 



Fig. 4. 



trans-Diamino diethylene- 



diamino-cobalti iodide. 



Calculated : 



64° 14' 

 43 46 

 35 51 

 83 57 '/2 



The crystals are slightly dichroitic: on a orange-red for vibrations 

 parallel to the c-axis, dark orange-red for such as are perpendicular 

 to them. The plane of the optical axes is [100]; the «-axis is first 

 bisectrix. The apparent axial angle is large, the dispersion is rather 

 strong, with q <^v round the a-axis. 



