272 11. L. Wheeler — Double Halides of Tellurium 



The Chlorides. 



The crystals of the three chlorides have a pale yellow color, 

 resembling that of the well known ammonium phospho-mo- 

 lybdate precipitate, the shade becoming somewhat lighter from 

 the caesium to the potassium salts. 



Ccesium tellurichloride, ICsCI. TeCl v — In the preparation 

 of this compound, and also in the preparation of the rubidium 

 and potassium double chlorides, the tellurium tetrachloride is 

 most conveniently made by converting tellurium into tellurous 

 oxide by means of aqua regia, evaporating to dryness to expel 

 nitric acid and then dissolving the residue in hot hydrochloric 

 acid. An aqueous solution of caesium chloride, added to this, 

 produces a precipitate, even in quite dilute solutions. There 

 must be an excess of hydrochloric acid present to prevent the 

 separation of tellurous acid. On boiling and adding more 

 water, if necessary, this precipitate dissolves. The solution, 

 left to cool, deposits small brilliantly lustrous octahedrons. It 

 is a general fact with these double halides, that an excess of 

 one or the other of the constituents does not affect their com- 

 position. This is shown in this particular case by the fact 

 that it can be recrystallized from strong solutions of tellurium 

 or of caesium chlorides. 







Analysis gave : 





Calculated. 



Cs 



43-44 



43-90 



44-63 



44-04 



Te 



20-65 







21-41 



20-69 



CI 



35-93 



35-14 





35-27 



This compound is perfectly stable in the air. It does not 

 melt below the boiling point of sulphuric acid. It can be 

 precipitated from its solution in dilute hydrochloric acid by 

 the addition of concentrated hydrochloric acid. A portion of 

 the salt, finely pulverized, was treated with water at ordinary 

 temperature. This produced a voluminous white precipitate, 

 which was washed with cold water and dried in the air. 



Analysis gave : Calculated for H 2 Te0 3 . 



Te 71-43 71-43 



H„0 7-52 10-29 



Ol 17-76 18-28 



CI 2-49 



Cs 0-80 



The oxygen which was not given off in the form of water 

 on heating the substance was calculated by difference. . From 

 the above analysis the conclusion may be drawn, that the pre- 

 cipitate produced by the action of water on this salt is essen- 

 tially tellurous acid, a small amount of oxychloride of tellurium 



