H. L. Wells — Cceshtm-Mercuric Halides. 235 



Csjilg B?\I 3 . — This compound lias a very faint tinge of 

 yellow. It is apparently dimorphous, although no other salt 

 of this type has been made in more than one form. It occurs 

 in very thin plates, like the chloride, bromide and chloro- 

 bromide, and in stout monoclinic crystals like the iodide. The 

 limits of the conditions under which the plates are made are 

 very narrow, and it is difficult to obtain them free from the 

 dimorphous crystals. As the solution cools, however, the 

 plates are deposited first, and, with the proper dilution, it is 

 possible to remove them and get the mother-liquor pressed out 

 with paper before the other crystals begin to form. There is 

 no difficulty in preparing the other modification of the com- 

 pound. 



, Found. s 



Ortborhombic Calculated for 





Thin plates. 



crystals. 



Cs 2 HgBr 2 I.. 



Caesium . 



... 30-71 



30-20 



30-23 



Mercury . 



... 24-14 



23-86 



22-73 



Bromine . 



. .. 21-05 



17-91 



18-18 



Iodine ... 



... 24-23 



28-50 



28-86 









100-13 100-47 100-00 



It is noticable that the plates, which resemble the bromide 

 in form, contain a small excess of bromine and a correspond- 

 ing deficiency of iodine. 



CsHgBrl^ — Only one form of this compound has been 

 prepared, although three other salts of this type are di- 

 morphous. Its form is monoclinic, like one modification of 

 the bromide, and it is pale yellow in color. 



Calculated for 

 Found. CsHgBrI 2 . 



Caesium 20-26 19*94 



Mercury 31*44 29-99 



Bromine 13-35 11-99 



Iodine 34*39 38-08 



99-44 100-00 



The Chloro-iodide, Cs 2 HgCIJ„_. 



This is the only combination of caesium chloride and mer- 

 curic iodide that could be produced. It is formed only in 

 very concentrated solutions containing a great excess of 

 caesium chloride. Its form is different from any other salt of 

 the type, for it occurs in slender, radiating needles. It is 

 snow-white in color, and when it is brought in contact with 

 water it instantly becomes bright red from the formation of 

 mercuric iodide. Two entirely separate crops were analyzed. 



