498 Mr. R. Sabine on the Motions produced 



With each battery-power the deoxidation was continued 

 during two or three hours, the readings being taken at inter- 

 vals. Weighings with higher battery-powers were impracti- 

 cable, on account of the adhesion of hydrogen bubbles around 

 the suspended disk. 



It appears from the above experiments that under water 

 and acidulated water the surface-tension of mercury is slightly 

 increased when deoxidized by an electric current, the deoxi- 

 dation under acid water appearing to be more complete than 

 under distilled water. When the mercurial surface was deoxi- 

 dized by means of sodium hyposulphite, the effect was similar 

 to that produced by the battery with acid water ; but the de- 

 oxidation did not appear to be so complete. 



The amalgamated copper disk of the previous experiments 

 was balanced as before ; and the weights required to detach it 

 from a surface of mercury in (1) distilled water, and (2) when 

 crystals of hyposulphite of soda were dissolved in it, were mea- 

 sured, as follows : — 



Liquid. Detaching weight. 



(9-58") 



(1) Distilled water < 9'57 >mean 9'58 grms. 



(2) Crystals of sodium hyposul- 



phite added 1 9-78 } „ 9-79 



Mercury being oxidized. 

 When a mercury surface is undergoing a process of oxida- 

 tion by the battery, it is, as we know, expanding correspond- 

 ingly with the atomic volume of the metal and that of its sub- 

 oxide. We are therefore prepared to find a greatly reduced 

 detaching weight, due, not to any change in the capillary con- 

 stant of mercury properly so called, but to an actual destruc- 

 tion of the surface itself. 



Measurements were made with the same amalgamated disk 

 whilst the mercury was being oxidized both under water and 

 under dilute sulphuric acid, with the following results : — 



Liquid. Detaching weight. grms. 



Circuit open 9'59 



f Electromotive force = f 9*561 n K „ 



1-0 Danielli 9-58 ) mean 9 " 57 



f 9'55 1 

 Distilled water -4 „ 6*2 „ < QmKK y ,, 9'55 



it 



55/ 

 niS I » 9-52 



(9-1 

 1 9-52/ 







Dilute suiphu- 1 » jj * 8 » ;;;;;;;;;;;;;;;;;; HI 



nc acid. I " 



