1889.] On Salts of a Base containing Chromium and Urea. 343 



thiocarbamide. It is hoped, however, that the work at present in 

 progress on this and kindred points will throw some light on the 

 relation which the chromium bears to the rest of the elements in these 

 complicated compounds. 



The remaining crystallographic determinations refer to compounds 

 described in the former paper (' Roy. Soc. Proc.,' vol. 33, p. 267). 



Platinum Salt of Chromium Urea. 



These crystals are minute prisms of yellowish-green colour, and 

 belong to the rhombohedral system. They are combinations of the 

 forms (101), (111), and (100). 



Calculated. Observed. 



aa l 60 6 60 1 



oa 90 90 41 



a^r 72 44 72 42 



r^ 34 32 34 31 



or 20 2-6 20 3 



The crystals were too minute to render any experiment for cleavage 

 possible. 



Chloride of Chromium Urea. 



In emerald-green stout crystals belonging to the rhombohedral 

 system. They are combinations of the hexagonal prisms (10l) with 

 (111) and (100) (figs. 1 and 2). 



FIG. 1. 



FIG. 2. 



