﻿PREPARATION OF AMMONIUM SELENATE. 



55 



Table I. 



Amount of 

 Ammon. Carb. 



Amount of 

 Bar. Selen. 



Time 

 Treated. 



Amount of 

 Water. 



Yield 

 Per Cent. 



0.7 



gram 



1 



gram 



15 



hrs. 



5 



cc. 



46.87 



0.7 



gram 



1 



gram 



29 



hrs. 



5 



cc. 



53.38 



0.7 



gram 



1 



gram 



35 



hrs. 



5 



cc. 



55.99 



1.4 



gram 



1 



gram 



18 



hrs. 



10 



cc. 



75.52 



1.4 



gram 



1 



gram 



24 



hrs. 



10 



cc. 



87,23 



1.4 



gram 



1 



gram 



39 



hrs. 



10 



cc. 



91.14 



2.8 



gram 



1. 



gram 



t 



hrs. 



10 



cc. 



40.36 



2.8 



gram 



1 



gram 



8 



hrs. 



10 



cc. 



62.50 



2.8 



gram 



1 



gram 



12 



hrs. 



10 



cc. 



74.21 



2.8 



gram 



1 



gram 



24 



hrs. 



10 



cc. 



87.23 



2.8 



gram 



1 



gj-am 



28 



hrs. 



10 



cc. 



96.35 



2.8 



gram 



1 



gram 



36 



hrs. 



10 



cc. 



97.65 



2.8 



gram 



1 



gram 



61 



hrs. 



10 



cc. 



97.65 



This table slio\\s that a large excess of "ammonium carbonate" 

 is required, a near theoretical yield being obtained only with five 

 equivalents of ''ammonium carbonate" to one of barium selenate. 

 The use of "ammonium carbonate" in excess of 2.8 grams is not 

 advisable, since this quantity will not dissolve in the amount of 

 water used. The above table also shows that the reaction takes 

 place slowly, about thirty hours being required to obtain a yield 

 approximately theoretical. 



Table II. ■ 



In the following table one gram portions of barium selenate 

 were treated with 2.8 gram portions of "ammonium carbonate" 



in small beakers. 







Time 



Amount of 



Yield 



Treated. 



Water. 



Per Cent. 



17 hrs. 



15 cc. 



72.91 



17 hrs. 



20 cc. 



63.80 



17 hrs. 



25 cc. 



57.29 



17 hrs. 



30 cc. 



49.48 



28 hrs. 



15 cc. 



83.33 



28 hrs. 



20 cc. 



82.03 



28 hrs. 



25 cc. 



72.91 



28 hrs. 



30 cc. 



60.01 



This table shows that it is more advantageous to use concen- 

 trated solutions of "ammonium carbonate," since the yields are 

 larger. 



