330 Mr. E. Wilson. Aluminium as an Electrode 



Laurie. ' Phil. Mag,,' 18S6, Series 5, vol. 22, p. 213. Investigates 

 the effect of amalgamating aluminium, and points out the important 

 part played by the oxide or suboxide of aluminium. 



Streintz. ' Wied. Ann.,' 1887, vol. 32, p. 116; also ibid., 1888, 

 vol. 34, p. 751. Suggests a kind of dielectric polarisation distinct 

 from ordinary electrolytic polarisation as cause of the apparent high 

 resistance of aluminium. 



Herroun. 'Phil. Mag.,' March, 1889. Refers to the disconformity 

 of aluminium in voltaic cells with ordinary theory. 



Hutin and Leblanc. ' Etude sur les Courants Alternatifs et leurs 

 Applications Industrielles,' Part 2, Chap. 10, p. 135. 



Graetz. ' Wied. Ann.,' 1897, vol. 62, No. 10, pp. 323327 ; also 

 * Journ de Phys.,' 1898, Series 13, vol. 7. This paper specially deals 

 with alternate currents and will be referred to again. With regard 

 to direct currents, Graetz gives 22 volts as the electromotive force 

 which aluminium as anode is able to oppose. 



Pollak. ' Comptes Rendus,' 1897, vol. 124, p. 1443. With alka- 

 line solutions, Pollak says he can overcome 140 volts continuous 

 pressure. Proposes to use aluminium as one pole of a cell for the 

 purpose of producing a uni-directional current from alternate 

 currents. 



Lang. 'Wied. Ann.,' 1897, vol. 63, pp. 191194. Uses an 

 electric arc with aluminium and carbon poles for the purpose of 

 rectifying an alternate current. 



PART I. 

 Direct Currents. 



Two sizes of cells have been used in these experiments, each 

 having aluminium and carbon electrodes. The large size consists 

 of one aluminium plate, -^ inch thick, and one carbon plate, \ inch 

 thick, separated by ebonite bolts and nuts, the distance between the 

 plates being J inch. The surfaces thus opposed to one another in an 

 electrolyte of saturated potash alum in water have each an area of 

 36 square inches. The aluminium plate was not bought as being 

 specially pure, and may have 2 per cent, impurities. After making 

 preliminary experiments with alternate and direct currents over a 

 lapse of four days, the following experiment was made with this cell 

 and was repeated. 



An exploring electrode was inserted midway between the plat( 

 and consisted of a platinum wire sealed into a glass tube. The wii 

 beyond the tube had a length of about 2 inches, and was coiled int 

 a small spiral, the plane of the spiral being parallel with the surfa< 

 of the plates. A Kelvin quadrant electrometer was arranged with 

 two-way switch, so that the potential between this electrode an< 



