276 H. L. Wheeler — Double Halides of Tellurium 



the crystals of the hydrous compound can be obtained much 

 larger than those of the anhydrous salt, both Yon Hauer and 

 Wills selected these for their work, while the more easily ob- 

 tained anhydrous salt was overlooked. The hydrous salt is 

 readily distinguished from the anhydrous one by its deport- 

 ment on exposure to a dry atmosphere. The latter is stable, 

 but under these conditions the hydrous compound rapidly 

 effloresces, losing its luster, the faces of the crystals becoming 

 superficially covered with a light reddish yellow and opaque 

 layer of the anhydrous salt. Crystals which had been ex- 

 posed to dry air for several days and were completely covered 

 with this layer were found, on crushing, to remain unaltered 

 in the interior and to have still retained included water in 

 addition to their water of crystallization. This was shown by 

 the fact that the crushed crystals gave a stain of the mother 

 licpjor to filter paper. This property of the hydrous crystals 

 explains why Yon Hauer assigned three molecules of water to 

 this salt instead of two. The material for analysis of the 

 hydrous salt was selected from crystals varying in size from 7 

 to 13 mm in diameter. These were very rapidly crushed on 

 smooth filter paper, to remove included water, and immediately 

 corked up in the weighing tube and analyzed. A close exami- 

 nation of the fragments, before and after weighing, gave no 

 evidence of loss of water from the substance by efflorescence. 

 The analyses were from three different crops. 



Calculated for Calculated for 



Analysis gave : 2KBrTeBr 4 . 2H ; 0. 2KBrTeBr 4 . 3H 2 0. 



K 10-90 11-07 10-73 10-87 10'61 



Te... 17-59 17-29 17-46 17-38 16-96 



Br ... 66-35 66-36 66'34 66-74 65-1) 



HO .. 5-33 5-53 5-73 5-01 7*32 



These results make it evident that the salt contains two 

 molecules of water, and not three as has generally been sup- 

 posed. The water in this salt was determined by heating it in 

 an air bath to constant weight. The temperature was main- 

 tained between 150°-160°, and finally, to be sure that all the 

 water had been driven off, the residues were analyzed in two 

 eases. 



Calculated for 

 Analysis gave : 2KBr . TeBr 4 . 



K 11-71 11-52 11-44 



Te 18-29 18-58 18*30 



Br 70-25 70-09 70-26 



Analyses of products obtained by cooling hot saturated solu- 

 tions gave the following results : 



