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XIY. A Study of the Polarization upon a Thin Metal 

 Partition in a Voltameter. — Part I. By John Daniel*. 



[Plates HI. & IV.] 



Introduction, 



THE curious polarization phenomena of very small elec- 

 trodes in a sulphuric-acid voltameter bearing a strong- 

 current, accounts of which appeared in the Annalen during 

 the winter of 1892, suggested to Dr. L. Arons, of the Uni- 

 versity of Berlin, to try a very thin metal partition in a 

 voltameter, expecting, as he said, that there would he a deve- 

 lopment of heat at this partition, resulting in the destruction 

 of the partition. Dr. Arons used gold-leaf as a partition. 

 The gold-leaf was pasted with Canada balsam over a hole 

 about 15 millim. in diameter bored in a glass plate, which 

 was slipped into the groove of a wooden or vulcanite frame 

 in the middle of the voltameter. This did not give a tight 

 partition, but sufficed for the observation that there was not 

 even visible development of gas on the gold-leaf ; whereas 

 platinum '02 millim. thick, substituted for the gold-leaf, 

 showed profuse development of gas with the current-strength 

 used, even when punctured with a hole 2 millim. square. I 

 think Dr. Arons also tried the gold-leaf partition in a solution 

 of Ou or Ag salt, and observed that the metal was deposited 

 on the partition. 



At the suggestion and under the kind direction of Pro- 

 fessor A. Kundt and Dr. L. Arons I undertook a more 

 thorough investigation of the subject. Several problems pre- 

 sented themselves : — 



(1) By quantitative measurement to determine whether 

 there be a critical thickness below which there will be no 

 polarization at the partition, and 7 if so, to determine this 

 thickness. 



(2) To determine the other critical thickness for which the 

 polarization is as great as for very thick plates. 



(3) The quantitative measurement of this polarization with 

 the same current- strength for plates of various thicknesses 

 between these limits. 



(4) By varying the current-strength in these different cases, 

 to determine what function the polarization is of the current- 

 strength. . 



(5) To learn how the polarization in these cases varies with 

 the time during which a given current-strength flows, readings 



* Communicated by Prof. 0. J. Lodge, D.Sc, F.R.S. 



