ON THE SILVER VOLTAMETER 571 



in 58e one of the bowls (N) belonging to Professor VAN DIJK was employed. The area 

 of the kathode surface of this last bowl was 40 sq. centima only, and this is the smallest 

 k;i( bode area employed by us for currents of nominal value 1 ampere. The results of 

 observations 58a, I, d, and e are in remarkable agreement (Til 827, I'l 1828, 1 '1 1827, 

 and 1 11 827), and it appears that within the limits stated above the area of the kathode 

 has no influence on the deposit, conditionally, of course, that the concentration of the 

 electrolyte is within certain limits, and that the current density is not too great. In 

 some of our earlier experiments we used rotating kathodes ; the large platinum bowls 

 were rotated about 40 times per minute and stationary glass vanes were inserted in the 

 kathode liquid to prevent its uniform rotation. The steadiness of the current was 

 not appreciably affected by this motion, and had more satisfactory deposits been 

 obtained in the rotating lx>wls than in the stationary ones we should have no 

 hesitation in recommending the method. The deposits were much the same in 

 texture, however, and there was no difference in their masses. As an example we 

 may refer to 38a, 6, and c. 38a and 386 were rotated ; 38c was not. The masses of 

 the deposits were 7-03110, 7*03096 and 7*03108 grammes respectively. 



Size of Anodes. 



In most of our experiments it was impossible to estimate the extent of the 

 anode surface owing to the outer coating of the electrically deposited silver. The 

 silver plates generally used as anodes were abotit 5x5xO - 4 centims., and the 

 current density at an anode was therefore comparatively small. In observations 

 25c, 26c and 416 the anodes were very small silver discs, having a total area of 

 about 2 '5 sq. centims. at the commencement of the deposit, and about I sq. centim. 

 at the conclusion ; they were not coated with electrolytic silver. On one 

 occasion the mass of the anode disc at the commencement was 12 grammes only, 

 and 7 grammes of silver were deposited. This is an extreme case. The results of 

 the " small anodes " observations are as follows : 



25a 1-11825. 

 26c 37. 



416 27. 



According to SCHUSTER and CHOSSLEY,* a small anode may give a deposit which 

 is too small. LEDUct states the opposite of this, and MERRILL^ observed no 

 ' lillei-ence due to variation in the size of the anode. In the porous cup form GUTHE 

 found the size of the anode to be immaterial, but states that the drop of potential 



* SCHUSTER and CIUXSSI.F.Y, ' Roy. Soc. Proc.,' 50, p. 344, 1892. 

 t LKDUC, ' J. de Phys.,' 1, p. 561, 1902. 

 MERRILI., ' Phys. Rev.,' 10, p. 172, 1900. 

 GUTHK, ' Bull. Bureau of Stands.,' voL 1, p. 361, 1904. 



4 D 2 



