﻿o36 
  Prof. 
  K. 
  Olszewski 
  on 
  the 
  Determination 
  of 
  

  

  -cooled 
  by 
  an 
  amount 
  proportional 
  to 
  the 
  difference 
  of 
  the 
  two 
  

   pressures, 
  hydrogen 
  under 
  like 
  circumstances 
  becomes 
  heated. 
  

   As 
  is 
  well 
  known, 
  the 
  Kelvin-Joule 
  effect 
  has 
  been 
  applied 
  by 
  

   Hampson 
  and 
  Linde 
  to 
  the 
  production 
  of 
  liquid 
  air 
  on 
  a 
  large 
  

   scale. 
  So 
  far 
  as 
  the 
  liquefaction 
  of 
  hydrogen 
  is 
  concerned, 
  

   one 
  might 
  have 
  expected, 
  in 
  view 
  of 
  the 
  peculiar 
  behaviour 
  of 
  

   hydrogen 
  just 
  mentioned, 
  that 
  the 
  apparatus 
  of 
  Hampson 
  and 
  

   Linde 
  would 
  not 
  be 
  directly 
  applicable 
  for 
  this 
  purpose 
  ; 
  this 
  

   supposition 
  was 
  verified 
  by 
  experiment. 
  There 
  appeared, 
  

   however, 
  to 
  be 
  no 
  doubt 
  that 
  the 
  apparatus 
  of 
  Linde, 
  and 
  still 
  

   more 
  so 
  that 
  of 
  Hampson, 
  could, 
  with 
  suitable 
  modifications, 
  

   be 
  used 
  for 
  liquefying 
  hydrogen 
  * 
  : 
  it 
  being 
  merely 
  a 
  question 
  

   of 
  cooling 
  the 
  gas, 
  before 
  expansion, 
  below 
  the 
  temperature 
  

   corresponding 
  to 
  the 
  inversion 
  of 
  the 
  Kelvin 
  effect, 
  after 
  

   which 
  it 
  could 
  be 
  liquefied 
  by 
  expansion. 
  

  

  As 
  a 
  matter 
  of 
  fact, 
  this 
  gas 
  was 
  successfully 
  liquefied 
  by 
  

   means 
  of 
  apparatus 
  constructed 
  .on 
  the 
  above 
  lines 
  first 
  by 
  

   Dewar, 
  and 
  then 
  by 
  Travers 
  f. 
  These 
  investigators 
  used 
  liquid 
  

   air 
  for 
  cooling 
  the 
  hydrogen, 
  the 
  air 
  boiling 
  under 
  diminished 
  

   pressure, 
  whereby 
  the 
  apparatus 
  was 
  cooled 
  to 
  about 
  —200°. 
  

   The 
  question 
  arose 
  as 
  to 
  whether 
  so 
  strong 
  a 
  cooling 
  is 
  an 
  

   indispensable 
  condition 
  for 
  the 
  liquefaction 
  of 
  hydrogen 
  by 
  

   means 
  of 
  irreversible 
  expansion, 
  or 
  whether 
  a 
  more 
  moderate 
  

   amount 
  of 
  cooling 
  would 
  suffice. 
  

  

  This 
  question 
  could 
  be 
  readily 
  answered 
  without 
  the 
  

   necessity 
  of 
  undertaking 
  a 
  series 
  of 
  experiments 
  at 
  different 
  

   temperatures, 
  provided 
  the 
  temperature 
  of 
  inversion 
  of 
  the 
  

   Kelvin 
  effect 
  were 
  known 
  for 
  hydrogen. 
  

  

  This, 
  however, 
  had 
  not 
  been 
  experimentally 
  determined. 
  

   Theoretically 
  it 
  had 
  been 
  deduced 
  by 
  Witkowski 
  t 
  in 
  two 
  ways. 
  

   First, 
  by 
  assuming 
  the 
  thermodynamic 
  coincidence 
  of 
  the 
  

   inversion 
  temperatures 
  for 
  hydrogen 
  and 
  for 
  air 
  — 
  which 
  led 
  

   to 
  a 
  value 
  of 
  about 
  —46° 
  ; 
  secondly, 
  by 
  making 
  use 
  of 
  an 
  

   empirical 
  formula 
  given 
  by 
  Rose-Innes 
  §. 
  This 
  investigator 
  

   proposed 
  the 
  following 
  formula 
  for 
  determining 
  the 
  cooling 
  

   in 
  the 
  case 
  of 
  the 
  Joule-Kelvin 
  effect 
  : 
  

  

  a 
  o 
  

  

  * 
  Professor 
  Kammerling 
  Onnes 
  (Communications 
  of 
  the 
  Leyden 
  

   Laboratory, 
  no. 
  23, 
  p. 
  16, 
  1896) 
  pointed 
  out 
  the 
  possibility 
  of 
  liquefying 
  

   hydrogen 
  in 
  Linde's 
  apparatus, 
  and 
  stated 
  the 
  conditions, 
  based 
  upon 
  

   thermodynamical 
  similarity, 
  under 
  which 
  liquefaction 
  can 
  occur. 
  

  

  t 
  Phil. 
  Mag. 
  [6] 
  i. 
  April 
  1901. 
  

  

  X 
  Rozprawy 
  of 
  the 
  Cracow 
  Academy, 
  Section 
  of 
  Math, 
  and 
  Natural 
  

   vSciences, 
  xxv. 
  p. 
  247 
  (1898). 
  

  

  § 
  Phil. 
  Mag. 
  [5] 
  xlv. 
  p. 
  228 
  (1898). 
  

  

  