118 Broivning and Flint — Tellurium Dioxide. 



acetic acid. If these simple operations are properly carried 

 out, the precipitate will have become crystalline by the time 

 when the excess of ammonia has been reached ; the addition 

 of a few drops of acetic acid w T ill cause the precipitation to 

 become entirely quantitative when the solution has cooled, so 

 that no tellurium will be detectable in the filtrate by stannous 

 chloride ; the precipitate can be transferred, and safely and 

 rapidly washed with cold water, and dried to constant weight 

 at about 105° (or even up to just below low redness) in a 

 quarter of an hour*. Furthermore, the filtration can be per- 

 formed at the end of half an hour or so, or after 12 to 24 hours, 

 as most convenient. And, as shown by the experiments of 

 Table Y, selenium does not interfere, providing precautions 

 are taken. 



