350         Dr.  Gundry  on  the  Asymmetrical  Action  of  an 
corresponds  with  finiteness  of  velocity  of  reaction  as  worked 
out  by  Kriiger.  With  platinized  platinum  electrodes  charged 
with  hydrogen,  and  with  Pel  electrodes  less  strongly  charged, 
the  result : — 
Polarization  capacity  x  -y—  -    which  corresponds 
y/  Frequency' 
with  the  case  of  diffusion,  was  found.  The  same  result  was 
found  by  Schonherr  *  for  unplatinized  Pt  electrodes,  which 
were  kept  charged  by  an  applied  direct-current  E.M.F. 
The  evidence,  therefore,  for  the  reaction  H2  =  2H  taking- 
place  with  finite  velocity,  and  hence  giving  rise  to  polari- 
zation effects,  is  affirmative  with  palladium  under  certain 
conditions ;  but  not  so  with  platinum,  where  the  effect  corre- 
sponding with  diffusion  seems  to  hold. 
It  is,  however,  to  be  added  that,  at  higher  and  higher 
frequencies  the  diffusion  effect  becomes  of  less  and  less 
importance  ;  and  the  effect  due  to  the  finiteness  of  velocity 
of  reaction,  though  smaller  than  the  diffusion  effect  at  lower 
frequencies,  would  eventually  at  sufficiently  high  frequencies 
outweigh  it. 
Under  other  conditions  with  unplatinized  platinum  elec- 
trodes, the  initial  polarization  capacity  was  found  inde- 
pendent of  the  frequency.  This,  which  corresponds  with  the 
Helmholtz  double-layer,  would  introduce  no  asymmetry.  It 
is  thus  seen  that  the  nature  of  the  initial  polarization  capacity 
may  be  no  safe  criterion  as  to  the  asymmetry  that  may  arise 
at  higher  frequencies. 
Experiments  with  a  Platinum  Electrode. 
I  have  made  experiments  with  platinum  electrodes  in 
3  norm,  solution  of  sulphuric  acid  of  the  same  nature  as 
those  described  with  mercury  electrodes.  The  large  electrode 
was  a  piece  of  platinized  platinum  foil  about  4  sq.  cm.  in  area. 
A  platinum  wire  TL  mm.  diameter  was  sealed  in  the  end  of  a 
tube  and  then  cut  off  flush  with  the  glass.  This  formed  the 
small  electrode. 
The  arrangement  and  method  were  the  same  as  before, 
except  that  both  cathodic  and  anodic  direct-current  polari- 
zation were  used.  In  order  that  the  state  of  polarization 
of  the  small  electrode  might  be  determined,  I  measured  the 
potential-difference  between  it  and  a  third  electrode  of  zinc, 
which  dipped  in  a  second  beaker.     This   beaker  was  filled 
*    S  cliouherr,  Drude  Annalen,  vi.  p.  116  (1901). 
