Resistance of certain Amalgams ivith Temperature. 433 



Hence we arrive at the conclusion that in order to produce 

 the solution-pressure attributed to zinc 1*27 grams of the metal 

 would have to jjass into the ionic form per square centimetre 

 immersed, which is obviously not the case. 



There are other points — comparatively of detail — on which 

 it seems to me the theory of concentration-cells has been too 

 hastily applied, and without sufficient experimental confir- 

 mation : points bearing on the view that the electromotive 

 force at a contact depends only on the concentration of the 

 ions in solution. Some experiments are being undertaken in 

 the hope of clearing up the question involved; but in the 

 meanwhile it seems worth while to publish the above remarks 

 on the more fundamental subject of the existence of an electro- 

 lytic-solution pressure. 



East London Technical College, 

 August 1899. 



XLVII. On the Variation of the Resistance of certain Amal- 

 gams with Temperature. By R. S. Willows, JB.Sc, 1851 

 Exhibition Scholar*. 



THE experiments described in the following paper were 

 undertaken at the suggestion of Prof. Thomson to 

 investigate the alteration in the electrical resistance of 

 amalgams with change of temperature. The range of tem- 

 perature was from about 15° to 140° 0. The resistance, or 

 rather the change in resistance due to heating, was measured 

 at intervals of 4°, and curves plotted having temperatures for 

 abscissas and resistances for ordinates. The curves so obtained 

 showed irregularities^ and an attempt was made to determine 

 the cause of the peculiar variation in resistance that they 

 denoted. 



The change in the actual specific resistance of mercury 

 caused by the addition of foreign metals was not considered. 

 This has been done by Matthiessenf and Weber \ . 



For our knowledge of the variation in resistance experienced 

 by metallic conductors in general we are indebted to 

 Matthiessen §, who experimented on a large number of 

 specially purified metals and numerous alloys between tem- 

 peratures 0° to 100° ; Fleming and Dewar ||, who also tested 

 numerous pure metals and alloys in the form of wires, 

 extending their researches from 100° to about —180°; 



* Communicated by Prof. J. J. Thomson, F.R.S. 



t Phil. Mag. 1862, p. 171. 



X Wied. Annul 1880, vol. xxiii. p. 447. § Trans Roy. Soc. 1860. 



|| Phil. Mag. Oct. 1892, p. 326 ; Phil. Mag. September 1893, p. 271. 



Phil. Mao. S. 5. Vol. 48. No. 294. Nov. 1899. 2 H 



