254 Gooch and Beyer — Use of the Filtering Crucible. 



through the crucible and replaced by water from above until 

 the current no longer flows. The electrodes are disconnected, 

 the extension chamber easily slipped off, and the washing of the 

 crucible and its contents continued sufficiently, with care, 

 should the deposit be spongy, to give time enough in the 

 washing to properly soak out absorbed material. The crucible 

 and contents are dried, ignited, and weighed as usual. This 

 method of manipulation was also put to the test in the elec- 

 trolysis of copper sulphate. Experimental details are given 

 in Table III. The results show that there is no difficulty in 

 getting accurate results while maintaining continuous filtration 

 during the process, and that the time needed to complete the 

 action is somewhat shortened when the liquid is kept in cir- 

 culation by filtering. 



Fourth Process. 



Another form of apparatus, in which a porcelain filtering 

 crucible replaces the platinum filter crucible, is shown in 

 figure -i. In this apparatus, it is neces- 

 sary to make the connection from above 

 with the electrode inside the crucible, 

 and this is accomplished by a linked 

 platinum wire, as shown. In putting 

 together and using this apparatus, a 

 finely perforated disc of platinum foil 

 (c) is laid upon the more coarsely per- 

 forated bottom of the porcelain crucible 

 (A). Upon this disc, the asbestos felt (a) 

 is deposited in the usual manner. Plat- 

 inum clippings (h) form a layer of suit- 

 able thickness above the asbestos, and 

 upon this layer, and in contact with it, 

 is placed another perforated disc of 

 platinum foil to which is attached a 

 twisted wire (e) so linked that it may be 

 folded within the crucible. This ap- 

 paratus is ignited and weighed, and to it 

 is adjusted, as shown, a chamber to hold 

 the electrolyte. The other electrode (f), 

 enclosed within a funnel ( D) made from a thistle tube, is intro- 

 duced in the manner indicated. This apparatus is adapted 

 only to use in the method of continuous filtration, and it is 

 used exactly as in the Third Process. Experimental details 

 are given in Table IV. 



By either of the processes described, reasonably rapid and 

 accurate electrolytic determinations may be made without the 

 use of rotating motors or special stirring apparatus, and without 



