438 
Mr.  E.  F.  Burton  on  the  Properties  of 
Fig.  0. 
tube  from  90  in  L  around  to  90  in  R  was  8'8  times  the  re- 
sistance of  each  cm.  length  of  the  single  limbs.  So  that 
when,  as  in  case  cited  in  Table  I.,  the  electrodes  were  placed 
at  15  in  each  tube,  the  effective  distance  between  the  elec- 
trodes was   23*8  cms.,   and   therefore    the   strength  of   the 
118 
electric  field  was  -— —  =4*9  volts  per  cm.     Thus  the  absolute 
Zoo 
value  of  the  velocity  of  the  silver  particles  in  water  at  a 
temperature   of   11°  C.  would  be   19*6  x  10-5  cms.  per  sec. 
per  volt  per  cm. 
Such  measurements  required  that  the  specific  resistance  of 
all  the  solutions  should  be  carefully  obtained.  The  resistance- 
cell  used  is  shown  in  fig,  6.  Two  thick  platinum  disks 
(2*5  cms.  in  diameter)  were  fused  by 
means  of  welded  platinum  wires  into 
two  fine  glass  tubes  which  were  rigidly 
fastened  into  the  ebonite  lid  (L)  fitting  0 
into  the  glass  vessel  Gr.  The  disks  were 
thus  about  "75  cm.  apart.  A  thermo- 
meter, T,  was  supported  by  the  lid  so 
that  its  bulb  reached  close  to  the  upper 
disk.  The  constant  of  the  vessel  was 
taken  by  means  of  a  *01  normal  KC1 
solution  at  suitable  intervals  during 
the  course  of  the  work.  The  resist- 
ances were  determined  by  the  ordinary 
Wheatstone's  bridge  method,  the  effects 
of  polarization  being  annulled  by  means 
of  a  double  commutator  as  used  by 
Whetham*. 
Solutions  of  the  metals  platinum, 
gold,  silver,  bismuth,  iron,  and  lead 
were  formed,  and  the  values  of  the 
velocities  of  the  particles  under  unit 
electric  force  determined  as  given  in 
Table  II.  As  has  been  found  by  all  experimenters,  the 
particles  of  the  platinum,  gold,  and  silver  solutions  move 
toward  the  positive  electrodes,  showing  that  the  particles 
themselves  bear  a  negative  charge.  On  the  other  hand,  the 
particles  of  the  other  solutions  named  move  in  the  opposite 
direction,  corresponding  to  a  positive  charge  on  the  particles. 
The  velocities  given  have  all  been  determined  for  a  tempe- 
rature of  18°  C. 
*  Phil.  Trans,  vol.  cxciv.  A,  p.  321  (1900). 
