J. P. Cooke—Atomic Weight of Antimony. 111 
deposition of the insoluble oxi-iodide. Even the crystals of 
iodide of antimony, when kept in the light, slowly become 
opaque from the formation of the same oxi-iodide; while the 
odor and staining of the stopper of the bottle furnish abundant 
proof of the liberation of iodine. « The study of these phe- 
nomena was most interesting, and the results obtained will be 
described in another paper. It is sufficient for the present to 
say that they pointed out to us a great source of impurity in 
iodide of antimony, and fully explained the want of accordance 
in our analyses of the crystals of this substance as first pre- 
pared. It was evident that we could only hope to purify the 
material by distilling or subliming it in an atmosphere o. 
Inert gas; and we devised the apparatus represented in the ac- 
companying figure for this purpose, which we have since found 
very generally useful forall sublimations where the temperature 
required does not exceed that which can be measured with a 
lated temperature the precipitates of sulphide of antimony, 
aa: was so arranged that the character of 
