344 



Mr. E. Wilson. Aluminium as an Electrode 



of sufficient size 95 to 96 per cent, of the energy of the alternate 

 current can be changed into direct current. The efficiency of 

 such a system as shown in fig. 4 will obviously be the ratio of the 

 rate at which work is done on xy to the rate at which work is done 

 on the whole system by the alternate current machine. If this is to 

 be 95 per cent., then only 5 per cent, must be dissipated in the cells. 

 An important point in connection with the working of these cells 

 is the wearing away of the aluminium. The thin metal used in the 

 small cells above alluded to is perforated with small holes, but I 

 have not noticed so much deterioration in the thicker sheet. The 

 evaporation of the electrolyte is another matter which needs con- 

 sideration if the temperature is raised fairly high in working. 



Two Aluminium Plates in Alum Solution. 



These experiments were undertaken to find what effect as a con- 

 denser this metal with its film has with varying frequency tempera- 

 ture and current. The aluminium plates in the two large cells above 

 experimented upon were opposed to one another in a saturated alum 

 solution. The distance between them was |- inch, and the opposed 

 areas in the solution are 36 square inches on each plate. 



The important data have been collected in Table V. As a corn- 

 Table V. 



parison two plates of ordinary sheet iron of the same area and the 

 same distance apart as in the aluminium cell were placed in a saturated 

 solution of alum and placed in series with the aluminium cell. As 

 before the circuit included a Siemens dynamometer and non-induc- 

 tive resistance, and potentials were observed for different positions of 

 the phase across the non-inductive resistance, and each cell, by aid 

 of a Kelvin quadrant electrometer and revolving contact maker. 

 On account of the irregular wave form of the curves of potential and 



