550 



MR. F. E. SMITH, MR. T. MATHER, AND DR. T. M. LOWRY 



with a little sealing-wax. The silver plate was immersed in the solution just below 

 the surface, and the sealing wax which secured the folds of the filter paper was at 

 least 2 centims. above the surface of the electrolyte. The filter cup was supported by 

 three platinum wires from an ebonite ring. 



Fig. 1. 



Fig. 2. 



(2) The Richards Form (fig. 2). A platinum bowl was in general used for the 

 kathode, and the anode was of the same form as that of the Rayleigh voltameter. It 

 was, however, surrounded by a fine-grained porous pot instead of a filter paper, and 

 the electrolyte inside the pot was maintained at a lower level than the electrolyte in 

 contact with the kathode. Usually no appreciable change in the difference of level 

 resulted during an experiment, but a small syphon was frequently employed to ensure 

 an approximately constant difference. Two of the porous pots were made by the Akron 

 Insulator and Marble Company, of the United States of America, and were obtained 

 for us by Dr. GUTHE ; several were made by PUKAL, of Berlin ; and others were from 

 an unknown source. 



(3) The Syphon Form (fig. 3). The kathode was a platinum bowl and the anode 

 a silver plate or silver bowl coated with electrically deposited silver. When a silver 



Fig. 3. 



Fig. 4. 



plate was used, it was contained in a glass dish, the electrolyte in the latter being 

 connected with that in the platinum bowl by a glass syphon. Two sizes of syphon 

 were used ; one was 30 sq. centims. in its narrowest part and 30 centims. in axial 

 length, the other was 8 sq. centims. section and 20 centims. in axial length. 



(4) The Pot-Syphon-Bowl Form (P.S.B.} (fig. 4). In this the liquid in the syphon 

 was separated from that in the anode vessel by a porous pot. Any advantages of the 

 Richards form were thus combined with those of the syphon. 



