342 Mr. E. Wilson. Aluminium as an Electrode 



ture afc which these experiments were made, namely, 13|- for the 16 

 frequency, and 11J C. for the 98'5 frequency, the resistance of a 

 layer of the electrolyte of area equal to the area of the plate 

 submerged, and length equal to the distance between the electrode 

 and the plate, has a value of about 0'063 ohm. The curves of 

 potential in fig. 2 have been corrected for this, and the dotted lines 

 show the results. The average watts dissipated by electrolytic 

 hysteresis at the carbon and aluminium plates at 98'5 periods per 

 second, fig. 2, are 0'69 and4'5 respectively. This takes no account of 

 the resistance of the electrolyte, and has been obtained by taking 

 instantaneous products of potential and current at twenty equal 

 intervals during the period. During the first half -period work is 

 supplied at the carbon plate on the average at the rate of 4*1 watts ; 

 during the second half-period the plate does work on the system 

 at the average rate of 2' 7 watts. The aluminium plate returns 

 practically nothing to the system. 



In fig. 3, the frequency is 101, the ratio of the maximum coulombs 

 in the two halves of the period is 1*7, and the Siemens dynamometer 

 in the circuit registered 2O6 amperes. The average temperature 

 during this experiment was about 55 C., but had a maximum of 

 64 C. at the end of the test. Under these conditions, evaporation of 

 the electrolyte was rapid. The experiments on the resistance of the 

 electrolyte at this frequency and temperature give 0'033 ohm, and 

 the potential curves have been corrected, the result being shown by 

 the dotted lines. The average rate of dissipation of energy due to 

 electrolytic hysteresis at the aluminium plate during the period is 

 153 watts, whereas at the carbon plate this rate is only 9'8 watts. 

 We see that the maximum volts during the half period when the 

 maximum coulombs are a minimum have risen to 13, whereas during 

 the other half period the maximum volts are only 7^-. 



The paper by Graetz already alluded to, deals with alternate 

 currents ; and two groupings of cells with aluminium plates as the 

 one electrode are given, whereby he proposes to rectify alternate 

 currents. He gives 22 volts as the potential an aluminium cell is 

 capable of opposing, and states that the current could not be 

 measured with a delicate galvanometer. The first grouping of these 

 cells consists of placing between the poles of the alternator two 

 circuits in parallel, in each of which he places four cells in series. 

 The poles are reversed so that in the one circuit the predominating 

 current will be positive, whereas in the other it will be negative. 

 The other grouping of these cells is shown in fig. 4, and the author 

 states that he gets a unidirectional current in the circuit xy. In 

 this circuit he has operated a direct current motor, and deposited 

 copper. By superposing one of tho current curves in figs. 1, 2, or 3 

 on the same curve, but with reversed phases, one can form an idea 



