with Potassium, Rubidium and Cwsium. 277 



Calculated for 

 2KBrTeBr 4 . 



K 11-67 11-70 11-44 



To 18-06 18-30 



Br 70-24 70-20 69'40 70-26 



The Double Iodides. 



, These salts are all black. The powder of the caesium salt is 

 pure black, that of the rubidium aud potassium salts is grayish 

 black. 



Caesium telluriiodide, %CsI . Tel^. — In order to prepare this 

 salt, and also in the case of the rubidium and potassium com- 

 pounds, tellurium tetraiodide was made by treating tellurous 

 oxide with hydriodic acid. The iodide of tellurium is spar- 

 ingly soluble in hydriodic acid, but, on mixing this solution 

 with a solution of caesium iodide, an amorphous black precipi- 

 tate was obtained, even in very dilute solutions. 



Calculated for 

 Analysis gave : 2CsI . Tel> 4 . 



Cs 23-37 23-07 



Te 10-51 10-84 



I 65-17 66-09 



This compound resisted all attempts to prepare it in a crys- 

 talline form. It is insoluble in csesium iodide and in hydriodic 

 acid, hence warming in the mother liquor failed to dissolve the 

 salt. It is decomposed slowly by cold water, rapidly by hot, 

 and apparently tellurous acid or anhydride separates. This 

 generally is impure, being mixed with a dark colored residue 

 containing iodine. On exposure the salt slowly loses iodine. 

 In the open capillary it does not melt below the boiling point 

 of sulphuric acid. 



Rubidium telluriiodide 2RbI. Tel^. — This compound was 

 prepared by mixing the constituents in the same manner as in 

 the preparation of the corresponding caesium salt. If the solu- 

 tions are only moderately concentrated, a black amorphous 

 precipitate is produced. Unlike the corresponding caesium 

 salt, it dissolves, to a slight extent, on warming in the mother 

 liquor, and on cooling, black microscopic octahedrons are pro- 

 duced. 



Calculated for 

 Analysis gave : 2EbI . Tel 4 . 



Rb 16-83 16-17 



Te 11-81 



I 72-07 72-02 



This iodide is stable on exposure. Water effects the same 

 decomposition as in the case of the caesium salt. A small por- 

 tion of this salt dissolves in strong alcohol, giving the color of 

 a weak iodine solution. 



