116 Browning and Flint — Tellurium Dioxide. 



solution of the alkali. The results of two experiments with 

 mixtures of bismuth and tellurium oxides are given in 



Table 



IV. 



Table IV. 









Te0 2 taken 



Bi 2 3 taken 



Te0 2 found 



Error 





grm. 



grm. 



grm. 



grm. 



(l) 



0-2027 



0-005 



0-2015 



-0-0012 



(2) 



0-2009 



005 



0-1997 



-0 0012 



In both cases, the mixed oxides were heated with two cubic 

 centimeters of potassium hydroxide solution (10 per cent), the 

 precipitate filtered out, and the filtrate diluted with hot 

 water and precipitated by addition of acetic acid. 



If hydrochloric acid solutions of tellurium and selenium 

 dioxides be mixed, abundantly diluted with boiling hot water, 

 and the operation of the above described process properly 

 applied, only the tellurium is precipitated, the selenium 

 remaining entirely in solution in the filtrate. This not only 

 provides a simple and rapid preparative process for the purifi- 

 cation of tellurium from selenium, but also makes possible the 

 estimation of tellurium directly in the presence of the latter 

 element. 







Table Y. 









Te0 2 taken 



Se0 2 taken 



Te0 2 found 



Error 





grm. 



grm. 



grm. 



grm. 



(1) 



0-2015 



0-2 



0-2010 



— 0-0005 



( 2 ) 



0-2013 



o-i 



0-1996 



— 0-0017 



(3) 



0-2003 



0-1 



0-1992 



— 0-0011 



(4) 



O--2009 



o-i 



0-2003 



— 0-0006 



(5) 



0-2000 



o-i 



0-2002 



+ 0-0002 



(6) 



0-2015 



o-i 



0-2016 



+ 0-0001 



(<) 



0-2038 



o-i 



0-2040 



+ 0-0002 



(8) 



0-2028 



0-05 



0-2019 



-0*0009 



(9) 



0-2024 



0-05 



0*2024 



o-oooo 



Experiment 1 in Table Y was made upon 0*2 grm. of 

 Te0 2 in the presence of 0*2 grm. of Se0 3 , which was later found 

 to contain a little copper. After solution of the oxides in two 

 cubic centimeters of hydrochloric acid and dilution to 200 cubic 

 centimeters with hot water, precipitation was effected as usual 

 by ammonia and acetic acid. Copper was carried down in the 

 precipitate, as shown by its greenish color, the total weight 

 after thorough drying being 0*2054 grm. In order to deter- 

 mine the amount of TeG 2 per cent, the precipitate was washed 

 with ten per cent potassium hydroxide solution, the tellurium 

 being carried away in solution as tellurite; the residue was 



