Passage  of  Electricity  through  Liquids.  373 
where  the  values  M  and  M',  just  as  the  corresponding  eand  e', 
may  be  positive  or  negative- 
In  the  middle  of  the  thread  of  liquid  the  composition  and 
concentration  are  not  changed :  for  each  quantity  M  or  M! 
which  emerges  from  a  section,  the  same  quantity  M  or  M'  comes 
on  the  other  side  from  the  adjacent  section.  It  is  different  at 
the  electrodes,  at  the  ends  of  the  thread  of  liquid,  where  the 
electrical  current  enters  or  emerges.  Here,  according  to  the 
direction  of  the  motion  (or,  what  is  the  same  thing,  according  t-> 
the  sign  of  M  or  M'),  sodium-  or  chlorine-molecules  may  accu- 
mulate or  be  carried  away. 
For  the  moment  we  know  nothing  as  to  the  sign  and  quantity 
of  M  and  M'.  Assuming  now  that  both  are  positive,  and  the 
number  of  removed  equivalents  of  sodium  are  greater  than  the 
number  of  removed  equivalents  of  chlorine,  or 
m>4m', 
a' 
in  the  last  section,  in  which  the   electrical    current  emerges 
from  the  thread  of  liquid,   M'   parts  by    weight   of  chlorine 
meet  with  —  M'  parts  by  weight  of  sodium,  and  combine  to  form 
■ 
f  1  +  -j  )  W=/m  parts  by  weight  of  neutral  salt.     There  remain 
then  in  the  last  section, 
wi=M-"M' (9«) 
parts  by  weight  of  sodium  ;  that  is,  they  are  here  separated  on 
the  positive  side  of  the  x,  at  the  so-called  negative  electrode  or 
cathode. 
Simultaneously  from  the  first  section  of  the  thread  of  liquid, 
in  the  unit  of  time,  M  parts  by  weight  of  sodium  have  come  out, 
and,  of  the  —  M  parts  by  weight  of  chlorine  which  have  been 
united  with  them,  only  M'  parts  by  weight  have  been  carried 
away.     There  thus  remain  —  M  —  M'  parts  by  weight  of  chlorine 
a. 
uncombined  at  the  positive  electrode  or  anode;  if  this  be  de- 
signated by  m'j  we  have 
ro'=_-(M-^M'\     ....     (9  b) 
a.  \  a.       J 
where  the  negative  sign  denotes  that  m'  is  separated  at  the  anode 
on  the  negative  side  of  the  x. 
Hence  the  first  section  of  the  thread  of  liquid  has  become 
