230 //. L. Wells — Caesium-Mercuric Haliden. 



Calculated 

 Found. forCs 3 HgI 5 



Caesium 33-02 32-33 



Mercury 16-33 16-21 



Iodine.*..- 50-42 51-46 



99-77 100-00 



Its specific gravity taken in benzol was found to be 4*605. 



When this salt is dissolved in a small quantity of hot water 

 the compound Cs 2 HgI 4 crystallizes out on cooling, but with a 

 larger quantity of water everything remains in solution. 



CsJIgl^. — This salt is produced under wide limits of condi- 

 tions by cooling solutions of the component salts when caesium 

 iodide is in excess. The monoclinic crystals vary in habit, 

 forming long prisms, nearly square plates or intermediate 

 forms. They are often obtained of very large size, sometimes 

 extending completely across the bottom of the vessel contain- 

 ing the solution and turning upwards at the ends besides. 



Calculated 

 Found. for Cs 2 HgI 4 . 



Caesium 27*32 27-39 27-31 



Mercury 21-57 21*21 2053 



Iodine 51-41 51-49 52-16 



100-30 100-09 100*00 



Two determinations of the specific gravity, taken in benzol, 

 gave the numbers 4*799 and 4 8 12. 



The salt is decomposed by water, giving, according to the 

 quantity used, either one of the salts containing more mercuric 

 iodide or mercuric iodide itself. It is not dissolved or decom- 

 posed by alcohol. 



CsHgI 3 (. HJJ ?). — This salt is formed only within very nar- 

 row limits from solutions containing a little more mercuric 

 iodide or water than those from which the preceding salt is 

 obtained. These conditions are perhaps most easily reached 

 by dissolving the last salt in a small amount of hot water and 

 cooling. It often happens that the three salts Cs 2 Hg 3 I 8 , 

 CsHgI 3 and Cs„HgI 4 are successively deposited as a solution 

 cools, and it is consequently difficult to obtain the salt under 

 consideration in a pure state, but this was accomplished after 

 a great many trials with varying conditions. The compound 

 forms very thin transparent plates which usually radiate from 

 a point and are often of large size. By pressing on paper they 

 rapidly become opaque. Whether this is caused by molecular 

 re arrangement or loss of water of crystallization is not certain, 

 for, on account of the extreme thinness of the crystals, it was 



