﻿308 
  HoTborn 
  <& 
  Day 
  — 
  Thermoelectricity 
  in 
  Certain 
  Metals. 
  

  

  increasing 
  purity 
  of 
  the 
  metal, 
  the 
  gold 
  Au^^ 
  according 
  to 
  the 
  

   chemical 
  analysis, 
  containing 
  0*09 
  per 
  cent 
  iron 
  and 
  0*08 
  per 
  

   cent 
  copper, 
  while 
  the 
  two 
  other 
  specimens 
  were 
  very 
  pure. 
  

  

  In 
  order 
  to 
  obtain 
  some 
  idea 
  of 
  the 
  behavior 
  of 
  the 
  thermo- 
  

   elements 
  below 
  0°, 
  preliminary 
  observations 
  were 
  made 
  at 
  

   — 
  80° 
  and 
  —185°, 
  from 
  which 
  it 
  was 
  found 
  that 
  all 
  the 
  elemen- 
  

   tary 
  metals 
  with 
  the 
  exception 
  of 
  palladium 
  have 
  a 
  minimum 
  in 
  

   the 
  vicinity 
  of 
  —100°. 
  The 
  difference 
  between 
  observed 
  and 
  

   calculated 
  values 
  increase 
  as 
  the 
  temperature 
  is 
  diminished, 
  

   in 
  the 
  case 
  of 
  palladium, 
  however, 
  the 
  value 
  calculated 
  from 
  

   the 
  first 
  equation 
  agrees 
  very 
  well 
  with 
  the 
  observed 
  electro- 
  

   motive 
  force 
  at 
  —100°. 
  

  

  The 
  observed 
  electromotive 
  force 
  of 
  the 
  several 
  metals 
  in 
  

   microvolts 
  at 
  the 
  two 
  temperatures 
  mentioned 
  follows, 
  the 
  

   arrangement 
  being 
  the 
  same 
  as 
  in 
  the 
  large 
  table. 
  For 
  pur- 
  

   poses 
  of 
  comparison 
  the 
  values 
  obtained 
  experimentally 
  at 
  450° 
  

   and 
  950° 
  are 
  added. 
  

  

  950° 
  450° 
  —80° 
  , 
  -185° 
  

  

  AUj 
  15532 
  5270 
  —307 
  —130 
  

  

  Au, 
  15612 
  5314 
  —315 
  —166 
  

  

  Ag 
  17484 
  5320 
  —302 
  —160 
  

  

  Rh^ 
  12798 
  4422 
  —312 
  —235 
  

  

  Ir 
  11688 
  4146 
  —320 
  —283 
  

  

  90Pt, 
  lORu.. 
  9814 
  4102 
  —388 
  . 
  —534 
  

  

  90Pt, 
  lOPd.. 
  4068 
  1714 
  —87 
  —106 
  

  

  lOPt, 
  90Pd-- 
  2566 
  -290 
  4-146 
  -f240 
  

  

  Pd^ 
  10670 
  3296 
  —392 
  —774 
  

  

  The 
  platinum 
  wire 
  of 
  the 
  standard 
  element 
  to 
  which 
  all 
  the 
  

   others 
  were 
  referred, 
  was 
  further 
  compared 
  with 
  another 
  wire 
  

   {a 
  — 
  0-00388) 
  from 
  the 
  same 
  source 
  prepared 
  with 
  especial 
  care. 
  

   This 
  latter, 
  as 
  also 
  the 
  wire 
  Pd^, 
  upon 
  analysis 
  by 
  Prof. 
  Mylius, 
  

   showed 
  no 
  impurities 
  amounting 
  to 
  0*1 
  per 
  cent. 
  The 
  electro- 
  

   motive 
  force 
  of 
  these 
  two 
  platinum 
  wires 
  referred 
  to 
  the 
  same 
  

   platin-rhodium 
  wire 
  showed 
  a 
  difference 
  of 
  1° 
  at 
  a 
  temperature 
  

   of 
  1000°, 
  while 
  a 
  third 
  wire 
  of 
  pure 
  platinum 
  from 
  another 
  

   firm 
  differed 
  12° 
  at 
  the 
  same 
  temperature. 
  The 
  last 
  had, 
  

   however, 
  a 
  smaller 
  temperature 
  coefficient 
  (a 
  = 
  '00376) 
  and 
  

   was 
  in 
  all 
  probability 
  less 
  pure. 
  

  

  