﻿Volta 
  Electricity 
  of 
  Metals. 
  

  

  429 
  

  

  that 
  a 
  plate 
  of 
  any 
  metal 
  at 
  that 
  temperature 
  would 
  be 
  about 
  

   '4 
  volt 
  positive 
  to 
  a 
  standard 
  gold 
  plate 
  at 
  16° 
  C. 
  

  

  § 
  78. 
  The 
  approximate 
  numerical 
  values 
  of 
  the 
  temperature- 
  

   variations 
  are 
  given 
  in 
  the 
  following 
  table 
  : 
  — 
  

  

  Table 
  V. 
  

  

  Metal. 
  

  

  Approximate 
  

  

  range 
  of 
  

   Temperature. 
  

  

  Potential 
  of 
  

  

  metal 
  with 
  

  

  standard 
  

  

  gold 
  plate. 
  

  

  Both 
  at 
  16° 
  C. 
  

  

  Variation 
  of 
  

  

  potential 
  per 
  1° 
  C. 
  

  

  Standard 
  plate 
  kept 
  

  

  always 
  at 
  16° 
  C. 
  

  

  Aluminium, 
  polished 
  on 
  glass-paper 
  

   ,, 
  waxed 
  

  

  °C. 
  

   16-50 
  

   16-40 
  

   16-47 
  

   15-62 
  

   16-75 
  

   16-33 
  

   16-55 
  

   16-65 
  

   16-60 
  

   16-70 
  

   16-30 
  

   30-50 
  

   16-30 
  

   30-60 
  

   16-60 
  

   16-65 
  

  

  Volts. 
  

   + 
  1-10 
  

   + 
  -98 
  

   +1-30 
  

   + 
  -73 
  

   + 
  -58 
  

   + 
  -52 
  

   + 
  -20 
  

   + 
  -28 
  

   + 
  -12 
  

   + 
  -16 
  

  

  - 
  -05 
  

  

  + 
  -04 
  

  

  •00 
  

  

  - 
  11 
  

  

  Volts. 
  

   +•0043 
  

   + 
  •0032 
  

   + 
  •0045 
  

   + 
  •0013 
  

   + 
  •0016 
  

  

  About 
  --0010 
  

   -•0022 
  

   -•0007 
  

   -•0007 
  

   -•0004 
  

  

  About 
  --0035 
  

  

  About 
  --01 
  10 
  

   Very 
  small. 
  

  

  About 
  +-0015 
  

   -•0016 
  

   -0016 
  

  

  „ 
  alcohol-washed, 
  dry 
  ... 
  

   Zinc, 
  polished 
  on 
  glass-paper 
  

  

  i 
  Lead, 
  scraped 
  

  

  Tin, 
  polished 
  on 
  glass-paper 
  

  

  Iron, 
  polished 
  on 
  emery-cloth 
  

   „ 
  alcohol-washed,^?'^ 
  

  

  Silver, 
  polished 
  on 
  glass-paper 
  

  

  „ 
  alcohol- 
  washed, 
  dry 
  

  

  ,, 
  coated 
  with 
  glass 
  

  

  

  Copper, 
  polished 
  on 
  emery-cloth 
  ... 
  

  

  »> 
  »5 
  )J 
  )5 
  ••■ 
  

  

  Oxidized 
  Copper 
  

  

  It 
  must 
  be 
  clearly 
  understood 
  that 
  these 
  are 
  true 
  tempera- 
  

   ture-variations 
  and 
  not 
  permanent 
  changes 
  in 
  the 
  plate 
  caused 
  

   by 
  exposure 
  to 
  a 
  high 
  temperature. 
  

  

  X. 
  Elimination 
  of 
  Metal-Air 
  Potentials 
  by 
  Solid 
  Non- 
  

   conducting 
  Films 
  on 
  the 
  Metallic 
  Surfaces. 
  

  

  § 
  79. 
  As 
  very 
  great 
  differences 
  of 
  opinion 
  seemed 
  to 
  exist 
  

   as 
  to 
  the 
  part 
  played 
  by 
  the 
  layer 
  of 
  air 
  which 
  is 
  close 
  to 
  the 
  

   metallic 
  surface, 
  I 
  devised 
  a 
  method 
  in 
  which 
  it 
  should 
  be 
  

   removed 
  and 
  a 
  film 
  of 
  solid 
  non-conducting 
  material 
  of 
  a 
  

   very 
  different 
  chemical 
  nature 
  put 
  in 
  its 
  place. 
  A 
  copper 
  

   plate 
  which 
  had 
  been 
  polished 
  on 
  glass-paper 
  was 
  filed 
  with 
  a 
  

   clean 
  dry 
  file 
  which 
  had 
  not 
  been 
  used 
  for 
  any 
  other 
  metal. 
  

   Its 
  potential 
  with 
  the 
  standard 
  gold 
  plate 
  being 
  

  

  + 
  •045 
  v. 
  

  

  A 
  zinc 
  plate 
  was 
  prepared 
  in 
  an 
  exactly 
  similar 
  way, 
  and 
  

   with 
  the 
  copper 
  plate 
  gave 
  

  

  + 
  •655 
  v. 
  

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

  

  