MORSE AND SHUDDEMAGEN. — AN ALUMINIUM ANODE. 369 



tific and commercial investigations on the aluminium anode which have 

 been made since that date have had direct reference to its application 

 as a rectifier. 



III. Polarization Capacity in General. 



It has been known for a very long time that the changes produced in 

 an electrolytic cell by the passage of a current resulted in setting up 

 what is called the counter electromotive force of polarization. It was 

 also recognized at an early date that a corresponding polarization capa- 

 city was a property specific for each metal in a given solution under given 

 conditions of current density and temperature. Kohlrausch 1 was the 

 first to offer a formal theory in connection with measurements made on 

 various cells with an alternating current, and he showed that an equa- 

 tion of form 



iR = E sin at — L -= — p J idt 



should hold, p being the counter electromotive force of polarization, 

 which replaced the >y of the ordinary equation. The integrated 



form for the resulting wave contained a sine function and two exponen- 

 tials whose value was negligible under the conditions of the experiment. 

 If Kohlrausch's equation is true, it is evident that the current due to 

 polarization must lead the applied electromotive force by 90°, while the 

 lag due to inductance has the same value. He suggests the possibility 

 of compensating the lag due to inductance by the introduction into 

 the circuit of a polarization cell, of the proper size. The current 

 would thus be brought into phase with the applied electromotive 

 force, and the current curve would then have the same form and 

 position as if no inductance were present in the circuit. It has since 

 been shown that Kohlrausch's simple theory does not hold for all the 

 forms of galvanic polarization. It is possible to set up polarization 

 cells in which the phase shift has any value from zero to 90°. The 

 present theory has been given by Wien, Warburg, Elsa Neumann, and 

 Kriiger, 2 and the general equation for the polarization e. m. f. is 



E 



p = -77- sin 



Co 



»I>-(i-0] 



1 Pogg. Ann., 148, 43 (1872). 



2 Wien, Wied. Ann., 58, 37 (1896), and Drude's Ann., 8, 372 (1902); War- 

 burg, Wied. Ann., 67, 493 (1899); Neumann, Wied. Ann., 67, 499 (1S99); 

 Kriiger, Ztsch. f. Phys. Chem., 45, 1 (1903), and Drude's Ann., 21, 701 (1906). 



VOL. XLIV. — 24 



