INDEXEj  > 
THE 
LONDON,  EDINBURGH,  and  DUBLIN 
PHILOSOPHICAL     MAGAZINE 
AND 
JOURNAL    OF    SCIENCE. 
[SIXTH   SERIES.] 
APRIL    1906. 
XXXVIII.  On  the  Properties  of  Electrically  Prepared  Col- 
loidal Solutions.  By  E.  F.  Burton,  B.A.,  1851  Exhibition 
Scholar  of  the  University  of  Toronto,  Research  Exhibitioner 
of  Emmanuel  College,  Cambridge*. 
I.  Introduction. 
AS  a  result  of  experiments  by  Professor  McLennan  f  and 
the  writer,  it  was  found  that  when  a  cylinder  of  any 
metal  is  enclosed  within  a  second  one  of  the  same  material, 
insulated  from  it,  and  surrounded  by  air  or  other  gases,  it 
gradually  acquires  a  negative  charge,  and  after  a  short  time 
reaches  a  state  of  equilibrium  at  a  definite  potential  below 
that  of  the  enclosing  cylinder.  Several  different  metals  were 
tried  and  each  was  found  to  attain  a  definite  charge.  These 
results  led  to  the  conclusion  "  that  a  process  is  going  on  at 
the  surface  of  the  metal,  whereby  an  excess  of  positively 
charged  particles  is  being  continually  emitted,"  thus  leaving 
the  metal  itself  with  a  negative  charge. 
Some  time  ago  Bredig  {  found  that  by  means  of  electrical 
pulverization  of  metals  it  is  possible  to  produce  so-called 
colloidal  solutions  of  metals  in  very  pure  water.  Experi- 
ments on  these  solutions  have  hitherto  pointed  to  the  con- 
clusion that  they  consist  merely  of  suspensions  of  very  finely 
divided  metallic  particles.      The    fact    that   these    particles 
*  Communicated  by  Prof.  J.  J.  Thomson, 
t  Phil.  Mag.  vol.  vi.  (Sept.  ]903)  p.  343. 
X  Anorganische  Fennente,  Leipzig  (1901). 
Phil.  Mag.  S.  6.  Vol.  11.  No.  64.  April  1906.  2  F 
