Chemical Affinity in terms of Electromotive Force. 



193 



each case for several days before the observations were made, 

 the current passing being near to '00002 weber. Shortcir- 

 cuited for ten seconds. 





Electrodes not 



removed 



Electrodes removed, 



Period since cessation 



from the acid used 



rinsed, and placed in 



of the shortcircuiting. 



whilst the original cur- 



fresh acid (recently 





rent passed. 





boiled and just cooled) 

 before shortcircuiting. 







volt. 



volt. 



During 1st minute . 



Steady rise to 



•86 



Steady rise to *52 



2nd „ 



Further rise to 



•95 



Further rise to '55 



3rd „ 



>1 5) J) 



1-03 



„ ,. '56 



3rd-5tk „ 



)) >) }• 



111 



„ „ -58 



5th-10th „ 



>, „ „ 



1-24 



Attained maximum # 59 



10th-20th „ 





1-26 



Slight fall to '55 



20th-30th ., 



Attained maximum 1*27 



Further fall to -53 



30th-60th „ 



Constant at 



1-27 



„ „ -49 



60fch-120th „ 



Slight fall to 



1-265 



,. „ "44 



120th-180th „ 



„ 



1-26 



„ ., '42 



180th-240th „ 



)j >) >> 



1-25 



„ „ -40 



(II.) Electrodes exposing a surface of 3*2 square centims. 

 each, kept at potential- difference of 2*20 volts, the current 

 being near '000025 weber. Shortcircuited for ten seconds. 



Period since cessation 

 of the shortcircuiting. 



Electrodes not removed 

 from the acid used 

 whilst the original cur- 

 rent passed. 



During first 7 minutes 



7th-20th minute. 



20th-30th „ 



30th-60th „ 



60th-120tk „ 



120th-180th „ 



180th-240th „ 



Steady rise to 



Constant at 

 Slight fall to 

 Further fall to 



volt. 



•60 



•63 



•63 



•61 



•57 



•51 



•49 



Electrodes removed, 

 rinsed, and placed in 

 fresh acid (recently 

 boiled and just cooled) 

 before shortcircuiting. 



Steady rise to 

 Slight fall to 

 Further fall to 



volt. 

 •60 

 •54 

 •50 

 •34 

 •31 

 •29 

 •28 



75. The absolute mass of gas occluded by even moderately 

 large foil electrodes is but minute ; on Sprengelpumping at 

 a red heat a platinum-foil electrode of about 160 square 

 centims. total surface (about 16 centims. long, and 5 broad), 

 weighing four grammes, only barely recognizable traces of 

 hydrogen were obtained, even when the electrode had been 

 used for a long time and hydrogen copiously evolved from 

 its surface during electrolysis. The presence of occluded 

 hydrogen, however, can readily be observed by chemical tests 



