Gooch and Beyer — Use of the Filtering Crucible. 253 



pump. A stop-cock in the tube of the crucible holder is con- 

 venient but not necessary. 



The manner of using the apparatus is simple. First, the 

 weighed crucible, fitted in the usual manner with an asbestos 

 felt and containing the platinum clippings, is adjusted to the 

 glass chamber. The cell is pressed into the platinum triangle 



and set into the holder. The funnel which carries the wire 

 electrode is put in place. The cell is charged with the elec- 

 trolyte and the current is turned on. The electrolysis begins 

 and, under regulated action of the vacuum pump, the liquid 

 is drawn through to the receiver at a convenient rate. Usually, 

 before the upper electrode is uncovered the stop-cock is closed, 

 the suction pump disconnected, and the liquid drawn off from 

 the receiver and returned to the electrolytic cell. The pump 

 is again connected, the stop-cock is opened and filtration 

 begins again. 



Should the deposit be noticeably loose, it may be compacted 

 by allowing the cell to drain complete under the action of the 

 suction pump. The electrolyte is thus kept in circulation, and 

 loose particles of the deposit are held upon the filtering layer. 

 From time to time, the process of emptying the receiver and 

 filling the cell is repeated. When the electrolysis is complete, 

 as shown by proper testing of the filtrate, the liquid is drawn 



