270 II. L. Wheeler — Double llalides of Tellurium 



The methods by which the double halides were obtained 

 will be given with the description of the salts. 



Method of Analysis. 



The anhydrous salts were removed from the mother liquor, 

 and, after pressing on filter paper, were dried in the air. The 

 hydrous compounds were rapidly crushed on smooth filter 

 paper, and, as soon as it was certain that no included water 

 was retained by the fragments, they were placed in weighing- 

 tubes. Portions of about one-half a gram were taken for 

 analysis. In order to determine the halogens, silver sulphate 

 was added to the solution of the weighed sample in water 

 containing a little sulphuric acid. The silver halide was 

 washed, ignited and weighed in the usual manner. After the 

 removal of the excess of silver by means of hydrochloric acid, 

 tellurium was removed with hydrogen sulphide. This separa- 

 tion of tellurium, best in warm solution, has been found to be 

 complete in a few minutes and in a condition that admits of 

 filtration without inconvenience. The sulphide of tellurium, 

 filtered on asbestus in a Gooch crucible, was washed with 

 water containing a little hydrogen sulphide, then treated with 

 a solution of bromine in dilute hydrochloric acid, which 

 readily dissolves the moist sulphide. An excess of nitric acid 

 was then added to this solution and the whole evaporated on 

 the water bath, the resulting tellurous acid, being transferred 

 to platinum, was ignited and weighed as Te0 2 . The alkali 

 metals were determined by evaporating the filtrate from the 

 tellurium sulphide to dryness, with an excess of sulphuric acid. 

 The residues were then converted into normal sulphate by 

 ignition in a stream of ammonia, as suggested by Kruss for 

 potassium sulphate. In the case of the hydrous salts, water 

 was determined by heating them in an air bath to constant 

 weight; the residues were analyzed and found to correspond 

 in composition to the anhydrous salts. The atomic weights 

 nsed in the calculation of the results were the following : 



Te, 125; K, 39-1 ; Rb, 85-5 ; Cs, 133; CI, 35-5; Br, 80; I", 127. 



Solubility. 



The salts are all decomposed by water. The double bro- 

 mides, however, show an interesting difference in their deport- 

 ment with this reagent. Potassium tellurium bromide dis- 

 solves in a small amount of water, but, if an excess of water 

 is added, tellurous acid separates, as has been observed by 

 Wills.* Rubidium tellurium bromide also dissolves in a 



* loc. cit. 



