78 Mr. J. B. Henderson. Polarisation of [June 15,. 



centimetre as 4'4 daniells (4*7 volts), and increased more and more 

 with increasing intensity of the galvanic current. It is very improb- 

 able that this can be right. By supposing, however, that the resist- 

 ance of the decomposition cell is not independent of the intensity, 

 but decreases in a fixed manner with increasing intensity, the calcula- 

 tion of the same experiments gives small and constant values of 

 polarisation." 



FIG. 1. 



BATTER Y 



The- method Dr. Richarz used to find the polarisation in his investi- 

 gation v/as independent of the resistance of the electrolytic cell. The 

 battery electrolytic cell and a switch, Ci, were joined in closed circuit. 

 A t branch circuit containing a very high resistance, a galvanometer, 

 and another switch, c 3 , joined the two sides of the switch c\ (ci and c 2 

 were the two contacts of a Helmholtz's pendulum interrupter). When 

 c, was made there was a very small current through the galvanometer. 

 To determine the polarisation Ci was broken, and immediately after c% 

 also. In the short time between the interruption of Ci and c 2 a current 

 strong for the sensibility of the galvanometer went through it. The 

 polarisation was calculated from the deflection given to the galvano- 

 meter needle by the impact of the current, which was proportional to 

 the electromotive force of the battery minus the polarisation. In thia 

 way Dr. Richarz found values for the polarisation never greater than 

 2*6 volts with small wire electrodes, and also got the same maximum 

 with large platinum plates. 



The cell used in the present investigation was a cylindrical glass 

 vessel 10 cm. diameter and 12 cm. deep. The electrodes were rect- 

 angular plates of platinum foil 7 cm. long by 5'5 cm. broad, and were 

 stiffened by being mounted on rectangular frames made by bending 

 glass tubing (fig. 2). The tubing of these frames also served 

 to support the plates in vertical planes by being passed through 

 holes in a bar of wood placed across the mouth of the vessel. The 

 plates were immersed in the solution to a depth of 5 cm., having 

 their planes parallel and about 1 cm. apart. There were thus 

 55 sq. cm. of surface of each plate wetted. To find the polari- 



