Intelligence and Miscellaneous Articles, 553 



also do those of hydrochloric acid and ammonia ; but no simple nume- 

 rical relations between them can be perceived. — Liebig's Annalen 

 (Supplement), vol. v. p. 253. 



ON THE POLARIZATION OP THE ELECTRODES. 

 BY M. J. M. GAUGAIN. 



In a note which 1 had the honour to lay before the Academy some 

 time ago (ComptesRendvs, Dec. 24, 1855) I have shown that the elec- 

 tromotive force arising from the polarization of the electrodes has not 

 a constant value as was then generally believed. The force varies 

 with the intensity of the current and with the time ; but with a given 

 electrolyte and system of electrodes there is a limit which cannot be 

 exceeded, whatever be the duration of the electrolysis and the inten- 

 sity of the current. This maximum value of the electromotive force 

 I have had in view in the researches of which I am about to give an 

 account. 



Several physicists have endeavoured to determine the part which 

 each electrode takes in the polarization, and have arrived at entirely 

 different results. Poggendorff considered that each electrode played 

 an equal part in producing the electromotive force ; Lenz and Savel- 

 jew found, on the contrary, that the part of the cathode is greater 

 than that of the anode. I endeavoured in turn to solve the question 

 by using, as in my previous researches, the method of opposition, ar- 

 ranged in the following manner. In a cylindrical glass vessel I 

 placed a much smaller porous vessel, and filled both vessels with 

 the same liquid. The platinum plates used in the decomposition of 

 the liquid were placed in the outside vessel, and I placed a third plate 

 in the porous vessel ; this third plate, which is always outside the 

 circuit traversed by the current, undergoes no polarization, and may 

 be compared successively with each electrode when they are polarized 

 to saturation ; this comparison gives the measure of the two polari- 

 zations — of the anode and of the cathode. The porous diaphragm 

 protects the neutral plate from the hydrogen disengaged by elec- 

 trolysis. 



The following are the results I obtained in this way in a series of 

 experiments made on a mixture of nine parts by volume of distilled 

 water and one part of sulphuric acid : — 



By the polarization of the anode 193 



,, ,, cathode 157 



both 350 



Within certain limits the quantity of sulphuric acid added to the 

 water appeared to exercise no influence on the result, provided the 

 proportion was not less than a certain amount ; but when this be- 

 comes extremely small, the polarization of the cathode increases 

 without any appreciable modification in the polarization of the anode. 

 The following are the results obtained by electrolyzing pure water : — 



Polarization of the anode 193 



cathode 243 



both 436 



Phil Mag. S.4. No. 233. Suppl. Vol. 34. 2 



