73 



, X TV. Liirroi/i/riiforj/ Ti'ii'tluih'ih'dutrnini'-Cohalti-perchlorate. 

 Formula ; \Co {Aein)^\ (CIO,), . 



This salt was prepared from the corresponding /-bromide by means 

 of silver-perchlorate, and the concentrated solution afterwards slowly 

 evaporated at 15° C. 



From an aqueous solution, still containing a trace of the silver- 

 salt in excess, the salt crystallized in the form of beaulifnl, spheno- 

 idic crystals (fig. 17a), which immedialely showed the presence of 

 hemihedrical symmetry. From the pure solutions in most cases the 

 flat, rectangular crystals, reproduced in fig. 176 were obtained; they 

 had a brownish-red or brownish-yellow colour, and show more 

 constant angular values than the sphenoidic crystals, whose angles 

 oscillate and which possess considerable geometrical anomalies. 



Evidently these kinds of crystals are however quite identical. 



RJwmblc-hisphenoidic . 



a: 6;(.-= 1.0580:1:0,6806. 



Observed Forms-. 6 = {OlOJ, highly predominant, and reflecting 

 well ; the faces are however often spoiled, and then give multiple 

 reflections. Further m = jllOj, giving good images and about as 



a Fig. 17. h 



Laevogyralory Triethylenediarniue-Cobaitiperchlorate. 



large as c = jOllj, which form shows very lustrous faces ;;•= {101 j, 

 giving sharp images, and \ery well developed, about as large as 

 o = |lll!; <u = |llli on the contrary small, and rather dull, although 

 giving well defined images; a =\\Q0\, very narrow and dull. In 



