Mr.  J.  A.  Wanklyn  on  Water-Analysis  and  Water,       525 
vanoineter,  a  current  was  observed  the  direction  of  which  in 
the  liquid  was  from  the  ignited  platinum  wire  C  to  the  end  A, 
or  from  the  end  B  to  the  ignited  platinum  wire  C.  The  ends 
A  and  B  of  the  long  platinum  wire  behaved  thus  towards  the 
freshly  ignited  wire  C  like  platinum  wires  the  surfaces  of  which 
are  covered  with  oxygen  and  hydrogen. 
If  the  long  platinum  wire  of  the  glass  trough  was  replaced  by 
a  copper  wire  of  the  same  length  and  0*08  millini.  in  diameter, 
and  instead  of  the  dilute  sulphuric  acid  a  concentrated  solution 
of  pure  sulphate  of  copper  was  used,  the  polarization  at  the  boun- 
dary of  the  metal  and  the  liquid  was  infinitely  small ;  and  now, 
when  the  solution  of  sulphate  of  copper  was  poured  in,  there  was 
a  diminution  in  the  resistance  of  the  copper  wire.  The  resist- 
ance K  of  the  copper  wire  was  again  compared,  as  described 
above,  with  the  almost  equal  resistance  of  a  German-silver  wire, 
and  was  found  to  be,  at  15°*5  C, 
K  =  2-783  m.  u.,  or  2*728  m.  u., 
according  as  the  glass  trough  was  filled  with  air,  or  to  the  height 
of  50  millims.  with  a  sulphate-of-copper  solution. 
After  the  current  of  a  Grove's  battery  of  six  elements  had  been 
passed  for  about  an  hour  through  the  copper  wire  while  surrounded 
by  solution  of  sulphate  of  copper,  the  end  A,  where  the  current 
entered,  close  to  the  inside  of  the  glass  trough  was  eaten  away, 
while  the  end  B,  where  the  current  emerged,  was  coated  with 
freshly  precipitated  copper.  In  the  middle  the  copper  wire  was 
of  the  original  thickness;  towards  the  end  A  it  was  thinner,  and 
towards  B  thicker.  The  decrease  or  increase  was  greater  the 
nearer  the  part  of  the  wire  was  to  the  end  A  or  B,  and  the  dia- 
meter of  the  wire  at  B  was  now  0*104  millim. 
It  follows  from  these  experiments  that  an  electrical  current 
divides  between  metallic  and  liquid  (electrolyzable)  conductors, 
as  Kirchhoff's  laws  require,  and  that  in  many  cases  the  polari- 
zation produced  by  electrolysis  causes  only  an  apparent  excep- 
tion from  this  rule. 
[To  be  continued.] 
LXVI.  Water -Analysis  and  Water.  By  J.  Alfred  Wanklyn, 
Corresponding  Member  of  the  Royal  Bavarian  Academy  of 
Sciences*. 
THE  "ammonia  process"  of  water-analysis  which  was 
brought  out  five  years  ago  by  Chapman,  Smith,  and  my- 
self, has  now  become  of  sufficient  importance  to  repay  a  minute 
examination  into  its  validity  and  special  characteristics.     Not 
*  Communicated  by  the  Author. 
