OF ARTS AND SCIENCES. 103 



Analyses of Antimonious Oxi-Iodide. 



Whence it is evident that the material consists chiefly of SbOI; and, 

 by regulating the action, this substance can be thus obtained in a 

 nearly pure condition, as the last analysis shows. 



The chemical constitution of the precipitated oxi-iodide is also very 

 plainly indicated by the successive changes which it undergoes when 

 heated in an atmosphere of inert gas, especially if they are studied in 

 connection with the precisely similar changes which the well crystal- 

 lized, and therefore more definite, oxichloride of antimony (SbOCl) 

 undergoes under the same conditions as already described, page 63, of 

 this volume. We experimented on the oxi-iodide with the apparatus 

 also described and figured in our previous paper ; and we found that, 

 from the dried precipitate, when heated in a current of carbonic diox- 

 ide gas, antimonious iodide begins to sublime at 150°. At 200'^, the 

 sublimation became active, and continued until a definite amount of 

 Sbig has been driven off, when it wholly ceased. In external appear- 

 ance, the residue differed only slightly from the original substance ; but 

 when analyzed it gave the following result : — 



Analysis of residue after heating at 200°, until sublimation ceased. 



Weight taken. ^Tb^ined^'' % «^ I«^-- 



1.8853 1.1512 32.99 



On now heating the residue more intensely, it underwent no further 

 change until the temperature rose above 350° ; but, at a low red heat, 

 antimonious iodide again sublimed, and there was left, as the final 

 residue, beautifully crystallized antimonious oxide — both orthorhombic 

 prisms and octahedrons. The reactions were obviously these : — 



At 200°, 5 SbOI = Sb.O^Ig + Sblg. 

 At low red heat, 8 Sb.OJg = 5 SbPs + 2 Sblj. 



