142 



PROCEEDINGS OP TIIK AMKRKWN ACADEMY. 



permeable septum desired. These vessels were 50 millimeters high 

 and 20 in diameter; their walls were uol much over one millimeter in 

 thicl Their impurities were removed 1>\ boiling with nitric ai 'i 



and thorough washing with water. They were bus] ended in the solution 

 1>\ means of a platinum wire hung upon a glass hook, which insulated the 



win- from ill'- electric con- 

 nections. In four experi- 

 ments two concentric porous 

 CUDS were used, the annular 

 space between them being 

 charged with argentic oxide, 

 since Kalilr found this BUD- 

 Btance t<> diminish the re- 

 ducing action in old solutions. 

 This last arrangement was 

 soon abandoned, however. 

 By means of a siphon the 

 liquid within the cup was 

 alwa\ s kepi at a lower level 

 than that without, bo as to 

 prevent outward filtration. 



The cathodes consisted of 

 the large lipped crucibles al- 

 ready described ; the anodes 

 were bars 5x1x1 centi- 

 meters of the purest silver, 

 supported by silver u ires and 

 not enclosed in Biter paper; 

 and the electrolyte usually 

 contained 1<> per cent of pure 

 freshly prepared argentic 

 nitrate. 



The temperature of the 

 cell under investigation was 

 kept constant by means of 

 suitable baths. For a low temperature a mixture of pure ice and 

 a solution of amnionic nitrate answered well, and for the higher tem- 

 peratures a large beaker containing pure water was warmed from the 

 outside by enough encircling leaden steam-pipe to cause the ill sired 

 intensity of heat. 



-«V_ 



l'n. I i:i. 6.— POBOUS CUP VoLTAMKTER 



(| actual size). 



A. glass hook for supporting anode. B, glass 

 ring for supporting porous cup. C, silver anode. 

 1), porous cup. E, platinum cathode. 



