﻿540 
  Inversion 
  Temperature 
  of 
  Kelvin 
  Effect 
  in 
  Hydrogen. 
  

  

  during 
  a 
  single 
  expansion 
  amounted 
  to 
  several 
  atmospheres, 
  

   the 
  cooling 
  was 
  much 
  stronger; 
  in 
  these 
  experiments 
  a 
  small 
  

   cylinder, 
  of 
  0*6 
  litre 
  capacity, 
  which 
  served 
  as 
  a 
  reservoir 
  for 
  

   the 
  gas 
  to 
  be 
  employed 
  during 
  each 
  expansion, 
  was 
  used 
  in 
  

   addition 
  to 
  the 
  large 
  cylinder. 
  With 
  such 
  an 
  arrangement, 
  

   there 
  is 
  a 
  cooling 
  due 
  to 
  the 
  performance 
  of 
  external 
  work 
  as 
  

   well 
  as 
  a 
  cooling 
  due 
  to 
  an 
  irreversible 
  expansion. 
  

  

  At 
  a 
  temperature 
  of 
  —78° 
  the 
  hydrogen 
  in 
  expanding 
  

   became 
  slightly 
  heated, 
  causing 
  a 
  galvanometer-throw 
  of 
  about 
  

   3 
  mm. 
  in 
  a 
  direction 
  opposed 
  to 
  that 
  formerly 
  obtained. 
  By 
  

   slow 
  pumping 
  and 
  the 
  resultant 
  lowering 
  of 
  temperature, 
  the 
  

   galvanometer-throws 
  were 
  gradually 
  reduced, 
  until 
  finally 
  at 
  

   — 
  -80°' 
  5 
  no 
  deflexion 
  was 
  noticeable. 
  A 
  further 
  lowering 
  of 
  

   temperature 
  produced 
  cooling, 
  and 
  at 
  —83° 
  this 
  gave 
  a 
  throw 
  

   of 
  5 
  mm. 
  in 
  the 
  opposite 
  direction. 
  

  

  Results, 
  

  

  From 
  the 
  above 
  experiments 
  it 
  follows 
  that 
  the 
  temperature 
  

   of 
  inversion 
  of 
  the 
  Kelvin 
  effect 
  for 
  hydrogen 
  amounts 
  to 
  

   — 
  80°*5. 
  This 
  number 
  agrees 
  fairly 
  well 
  with 
  the 
  value 
  

   deduced 
  by 
  Witkowski 
  from 
  the 
  equation 
  of 
  Rose-Innes 
  

   ^o 
  ( 
  — 
  79°*3). 
  This 
  agreement 
  between 
  the 
  tv\ 
  o 
  values 
  makes 
  it 
  

   interesting 
  to 
  calculate 
  the 
  critical 
  temperature 
  of 
  hydrogen 
  

   from 
  the 
  assumed 
  thermodynamic 
  similarity 
  of 
  the 
  critical 
  

   temperatures 
  of 
  air 
  and 
  hydrogen, 
  and 
  the 
  inversion 
  tempera- 
  

   ture 
  of 
  air 
  (deduced 
  by 
  Witkowski 
  from 
  Rose-Innes's 
  

   equation). 
  If 
  we 
  assume 
  the 
  critical 
  temperature 
  of 
  air 
  to 
  be 
  

   133 
  c 
  on 
  the 
  absolute 
  scale 
  (= 
  — 
  140° 
  C), 
  the 
  inversion 
  tem- 
  

   perature 
  of 
  hydrogen 
  to 
  be 
  3 
  92°*5 
  absolute 
  (= 
  — 
  80°'5 
  C), 
  

   that 
  of 
  air 
  633° 
  absolute 
  ( 
  = 
  + 
  360°C.), 
  then 
  we 
  obtain 
  for 
  the 
  

   critical 
  temperature 
  of 
  hydrogen 
  40 
  o, 
  4 
  absolute, 
  i.e. 
  — 
  232 
  0, 
  6C. 
  

   This 
  temperature 
  differs 
  from 
  that 
  found 
  by 
  me 
  experi- 
  

   mentally 
  * 
  (-234°-5 
  C.) 
  by 
  only 
  1°;9. 
  

  

  From 
  the 
  above 
  experiments 
  we 
  may 
  draw 
  the 
  conclusion 
  

   that 
  in 
  order 
  to 
  liquefy 
  hydrogen 
  by 
  means 
  of 
  the 
  Kelvin 
  

   effect, 
  it 
  is 
  not 
  absolutely 
  necessary 
  to 
  cool 
  it 
  below 
  —200°, 
  

   but 
  that 
  with 
  a 
  thermally 
  well-insulated 
  apparatus 
  the 
  

   temperature 
  of 
  about 
  — 
  100°, 
  which 
  is 
  easily 
  obtained 
  by 
  

   using 
  solid 
  carbonic 
  acid 
  and 
  ether, 
  is 
  already 
  sufficient. 
  

   There 
  is, 
  however, 
  no 
  doubt 
  that 
  a 
  stronger 
  cooling 
  by 
  means 
  

   of 
  liquid 
  air 
  helps 
  to 
  accelerate 
  the 
  liquefaction 
  of 
  hydrogen. 
  

   Cracow, 
  Chemical 
  Institute 
  of 
  the 
  Jagellon 
  University. 
  

  

  " 
  * 
  Rozpraicy 
  of 
  the 
  Cracow 
  Academy 
  ; 
  also 
  Phil. 
  Mag. 
  [5] 
  xl. 
  p. 
  202 
  

   (1895). 
  

  

  