with Potassium, Rubidium and Caesium. 275 



This salt remains unaltered in the air. It can be separated 

 from its solution in dilute hydrobromic acid by the addition 

 of concentrated acid. It does not melt below the boiling 

 point of sulphuric acid. Attempts to prepare a hydrous salt 

 according to the methods used for the preparation of TeBr t . 

 2KBr . 2H 3 were without success. 



Rubidium teliuribromide, %RbBr . TeBr^ — The directions 

 given for the preparation of the corresponding caesium com- 

 pound apply also in the preparation of this salt. If the solu- 

 tions are strong, the compound separates as a bright red pre- 

 cipitate, but if dilute, on concentrating by means of heat or 

 spontaneous evaporation, it crystallizes in brilliant red octa- 

 hedra. 



Analysis gave : Calculated. 



Rb 22-02 22-04 



Te 16-11 



Br 62-07 61-85 



This salt is stable in the air. Like the corresponding caesium 

 salt, this separates from its solutions by the addition of concen- 

 trated hydrobromic acid. When it is dissolved in a little 

 water and the solution is cooled slowly, colorless octahedrons 

 of Te0 2 separate. The latter product was found to be im- 

 pure, containing a small amount of bromine. On heating, the 

 salt decrepitates slightly and melts at a high temperature. 

 Efforts to prepare a hydrous salt according to the methods 

 used for the preparation of 2KBr . TeBr 4 . 2H 2 were without 

 success. 



Potassium telluribromides, %KBr . TeB?\ and %KBr . 

 TeBr i . 1HJ)* — For the preparation of these salts, a mixture 

 of the constituents was made as described in the case of the 

 caesium double bromide. The solution invariably deposited 

 crystals of the anhydrous salt when it had been concentrated 

 by heat, but, by spontaneous evaporation of the filtrate, the 

 hydrous salt was obtained. On recrystallizing either of these 

 salts from water or from dilute hydrobromic acid, the anhy- 

 drous salt is obtained when the solution has been saturated by 

 boiling and then allowed to cool, but if the solution is left to 

 deposit crystals at ordinary temperature the hydrous modifica- 

 tion is obtained. The crystals of these different compounds 

 closely resemble each other in color and appearance. The 

 anhydrous variety crystallizes in octahedrons modified by the 

 cube. The orthorhombic crystals of the hydrous salt look like 

 distorted crystals of the other. This being the case, and since 



* Described by Von Hauer as containing three molecules of water of crystalliza- 

 tion. 



Am. Jour. Sci.— Third Series, Vol. XLV, No. 268.— April, 1893. 

 20 



