﻿Volta 
  Electricity 
  of 
  Metals. 
  

  

  413 
  

  

  directly 
  to 
  metals 
  which 
  have 
  been 
  cleaned 
  by 
  means 
  of 
  a 
  

   hard 
  dry 
  agent 
  only. 
  Even 
  in 
  the 
  experiment 
  which 
  he 
  gives 
  

   on 
  pp. 
  79-80 
  of 
  his 
  paper 
  as 
  a 
  proof 
  that 
  alcohol- 
  washing 
  

   does 
  not 
  permanently 
  alter 
  the 
  potential 
  of 
  a 
  clean 
  gold 
  plate, 
  

   he 
  appears 
  to 
  have 
  used 
  a 
  plate 
  which 
  had 
  already 
  been 
  

   washed 
  with 
  alcohol 
  ; 
  his 
  result, 
  therefore, 
  does 
  not 
  prove 
  that 
  

   alcohol-washing 
  makes 
  no 
  change 
  in 
  contact-potential 
  of 
  a 
  

   clean 
  plate, 
  but 
  only 
  that 
  subsequent 
  washings 
  do 
  not 
  alter 
  

   the 
  state 
  of 
  surface, 
  ?'. 
  e. 
  that 
  the 
  effect 
  is 
  nearly 
  permanent. 
  

   This 
  agrees 
  with 
  the 
  results 
  given 
  above 
  and 
  in 
  Table 
  II. 
  

  

  § 
  14. 
  The 
  alcohol 
  film, 
  whether 
  in 
  combination 
  with 
  the 
  

   metal 
  or 
  not, 
  must 
  in 
  any 
  case 
  displace 
  the 
  air 
  from 
  the 
  

   surface 
  of 
  the 
  plate. 
  Other 
  liquids 
  seem 
  to 
  leave 
  films 
  in 
  

   much 
  the 
  same 
  way, 
  though 
  the 
  change 
  of 
  potential 
  is 
  different 
  

   for 
  each 
  liquid 
  ; 
  in 
  some 
  cases, 
  e. 
  g. 
  turpentine 
  on 
  zinc 
  and 
  

   copper, 
  it 
  is 
  in 
  the 
  positive 
  direction 
  for 
  the 
  positive 
  metal 
  

   and 
  in 
  the 
  negative 
  for 
  the 
  other. 
  

  

  Table 
  II.— 
  Permanent 
  Changes 
  produced 
  in 
  Contact-potential 
  

   of 
  Metals 
  by 
  washing 
  with 
  A.ico'iol 
  and 
  drying 
  in 
  Air. 
  

  

  Metal. 
  

  

  Copper 
  

  

  Gold 
  

  

  Silver 
  

  

  Iron 
  

  

  Lead 
  

   Tin.. 
  

  

  Zinc 
  

  

  Aluminium 
  

  

  Previous 
  treatment. 
  

  

  Potential 
  with 
  standard 
  

   gold 
  plate. 
  

  

  Before. 
  

  

  Polished 
  on 
  glass-paper 
  

  

  Polished 
  on 
  emery-cloth 
  

  

  Filed 
  

  

  Oxidized 
  

  

  After. 
  I 
  Change. 
  

  

  Polished 
  with 
  dry 
  " 
  plate-powder 
  " 
  

   Polished 
  on 
  glass-paper 
  

  

  volt. 
  

   -•20 
  

   + 
  09 
  

   + 
  02 
  

   -13 
  

   -•24 
  

  

  Dry-polished 
  

  

  Polished 
  on 
  emery-cloth 
  

  

  + 
  10 
  

  

  + 
  •08 
  

   + 
  ■17 
  

  

  Scraped 
  thoroughly 
  with 
  a 
  knife 
  

  

  Polished 
  on 
  glass-paper 
  

  

  Polished 
  on 
  glass-paper 
  

  

  Polished 
  on 
  glass-paper 
  

  

  + 
  •61 
  

  

  + 
  •56 
  

  

  + 
  •61 
  

  

  +1-05 
  

   +1-04 
  

   + 
  1-13 
  

   + 
  1-17 
  

  

  volt. 
  

   + 
  •22 
  

   + 
  •29 
  

   + 
  •14 
  

   + 
  •14 
  

   •00 
  

  

  + 
  •20 
  

  

  + 
  •16 
  

   + 
  •29 
  

  

  + 
  •80 
  

  

  + 
  •66 
  

  

  +•94 
  

  

  + 
  1-10 
  

   +107 
  

   + 
  1-28 
  

   +1-26 
  

  

  volt. 
  

   + 
  •42 
  

   + 
  ■20 
  

   + 
  12 
  

   + 
  •27 
  

   + 
  •24 
  

  

  +•05 
  

  

  + 
  •10 
  

  

  + 
  •08 
  

   + 
  •12 
  

   +47 
  

   +•14 
  

  

  + 
  •19 
  

  

  +•10 
  

  

  + 
  •33 
  

  

  +•05 
  

   +•03 
  

   + 
  15 
  

   + 
  •09 
  

  

  Phil. 
  Mag. 
  S. 
  5. 
  Vol. 
  45. 
  No. 
  276. 
  May 
  1898. 
  2 
  F 
  

  

  