Alternating  Current  on  a  Polarizable  Electrode.       353 
Summary. 
To  summarize  the  results  obtained  in  this  paper  : — 
(1)  It  is  shown  that  a  perfectly  symmetrical  alternating 
current  acting  at  a  polarizable  electrode  leads,  according  to 
the  osmotic  theory  of  polarization,  to  an  asymmetry  of  the 
polarization — in  other  words  to  a  direct  current. 
(2)  The  case  of  a  mercury  electrode  being  worked  out 
gives  as  a  result  that  the  direct  current  I  satisfies  the  relation 
NI 
—  =  const.,  where  N  is  the  frequency  and  z0sin  27rNt  is  the 
alternating  current.  The  direction  of  the  current  corresponds 
with  an  effective  diminution  of  the  concentration  in  the 
neighbourhood  of  the  electrode. 
(3)  The  same  relation  should  hold  when  the  electrolyte  is 
a  solution  of  a  complex  salt,  provided  that  diffusion  from 
and  to  the  layer  of  electrolyte  surrounding  the  electrode  plays 
the  important  part  in  the  polarization. 
(4)  In  cases,  however,  where  the  polarization  arises  (as 
described  by  Kriiger)  from  the  finiteness  of  the  velocity  of 
reaction  by  which  mercury  ions  are  supplied  from  the  com- 
plex molecules,  the  relation  -^  =  const,  holds,  being  inde- 
pendent of  the  frequency.  '° 
(5)  A  disturbing  effect  which  masks,  in  many  cases,  the 
above  described  one  is  accounted  for,  and  the  reasons  assigned 
why  in  certr\n  cases  this  disturbing  effect  is  absent,  or 
nearly  so. 
(6)  Experiments,  made  with  KCN  solution,  show  to  what 
NI 
extent  -r^  =  const,  is  found  to  hold  at  high  frequencies.     At 
low  frequencies  the  relation  is  totally  departed  from,  and 
there  appears  to  exist  a  critical  frequency  where  a  sudden 
change  in  the  phenomenon  takes  place. 
(7)  An  application  to  the  u  electrolytic  coherer  "  is  sug- 
gested on  the  supposition  that  the  equilibrium  in  some 
reaction  such  as  H2  =  2H  is  reached  with  finite  velocity,  and 
an  effect  corresponding  with  (4)  above  takes  place. 
(8)  Experiments  with  a  Pt  electrode,  both  anodically  and 
cathodically  polarized,  show  that  the  magnitude  of  the  direct- 
current  effect  varies  at  higher  frequencies  much  less  with  the 
frequency  than  is  the  case  with  the  mercury  electrode. 
The  above  work  was  done  in  the  Institute  for  Physical 
Chemistry  of  the  University  of  Gottingen ;  and  I  have  the 
pleasant  duty  of  thanking  Prof.  Nernst  and  Dr.  Kriiger  for 
placing  the  facilities  at  my  disposal  and  for  much  helpful 
interest  and  advice  during  the  work. 
