﻿382 
  Lmebarger 
  — 
  Some 
  Relations 
  between 
  Temperature, 
  

  

  simple 
  and 
  to 
  compound 
  bodies 
  without 
  distinction." 
  This 
  

   law 
  is 
  : 
  " 
  The 
  heats 
  of 
  vaporization 
  of 
  different 
  substances 
  

   range 
  themselves 
  exactly 
  in 
  the 
  order 
  of 
  their 
  temperatures 
  of 
  

   ebullition, 
  when, 
  instead 
  of 
  equal 
  weights, 
  atomic 
  weights 
  are 
  

   taken. 
  In 
  a 
  "Note" 
  three 
  years 
  later 
  Person* 
  reverts 
  to 
  his 
  

   law, 
  and 
  drawing 
  up 
  a 
  table 
  of 
  latent 
  heats 
  of 
  vaporization 
  

   from 
  the 
  data 
  due 
  to 
  Favre 
  and 
  Silbermann 
  shows 
  how 
  well 
  

   his 
  previous 
  statements 
  are 
  corroborated 
  by 
  these 
  determina- 
  

   tions. 
  The 
  exceptions 
  presented 
  by 
  the 
  acids 
  are 
  explained 
  

   away 
  by 
  making 
  allowance 
  for 
  their 
  abnormal 
  vapor 
  densities. 
  

   In 
  this 
  paper, 
  he 
  puts 
  his 
  law 
  in 
  a 
  somewhat 
  different 
  form 
  : 
  

   " 
  The 
  amount 
  of 
  heat 
  needed 
  to 
  vaporize 
  substances 
  under 
  the 
  

   same 
  pressure 
  is 
  identical, 
  when 
  the 
  volume 
  produced 
  is 
  the 
  

   same, 
  and 
  it 
  is 
  smaller 
  or 
  greater 
  according 
  as 
  the 
  volume 
  pro- 
  

   duced 
  is 
  smaller 
  or 
  greater." 
  

  

  Troutonf 
  " 
  on 
  comparing 
  the 
  quantities 
  of 
  heat 
  necessary 
  to 
  

   evaporate 
  at 
  constant 
  pressure 
  quantities 
  of 
  different 
  liquids 
  

   taken 
  in 
  the 
  ratio 
  of 
  the 
  molecular 
  weights," 
  — 
  found 
  that 
  the 
  

   amount 
  of 
  heat 
  required 
  by 
  any 
  body 
  is 
  approximately 
  pro- 
  

   portional 
  to 
  its 
  absolute 
  temperature 
  at 
  the 
  point 
  of 
  ebullition." 
  

   He 
  then 
  propounded 
  the 
  following 
  law 
  : 
  " 
  The 
  molecules 
  of 
  

   chemically 
  related 
  bodies, 
  in 
  changing 
  from 
  the 
  gaseous 
  to 
  the 
  

   liquid 
  state 
  at 
  the 
  same 
  pressure, 
  disengage 
  quantities 
  of 
  heat, 
  

   which 
  may 
  be 
  called 
  the 
  molecular 
  latent 
  heat, 
  directly 
  pro- 
  

   portional 
  to 
  the 
  absolute 
  temperature 
  of 
  the 
  point 
  of 
  ebulli- 
  

   tion." 
  

  

  The 
  above 
  laws 
  are 
  purely 
  empirical 
  ; 
  they 
  were 
  found 
  

   through 
  observation 
  of 
  rows 
  of 
  figures 
  ; 
  they 
  have 
  no 
  theoreti- 
  

   cal 
  grounding 
  ; 
  being 
  subject 
  to 
  exceptions 
  and 
  irregularities, 
  

   they 
  can 
  never 
  as 
  deduced 
  rise 
  to 
  the 
  rank 
  of 
  great 
  generaliza- 
  

   tions 
  ; 
  they 
  have 
  been 
  drawn 
  up 
  by 
  the 
  inspection 
  of 
  experi- 
  

   mental 
  data, 
  which 
  is 
  an 
  inversion 
  of 
  the 
  usual 
  order 
  of 
  dis- 
  

   covery, 
  experimental 
  data 
  as 
  a 
  rule 
  being 
  a 
  means 
  of 
  corrobora- 
  

   tion 
  rather 
  than 
  of 
  deduction 
  of 
  laws 
  of 
  nature. 
  

  

  We 
  now 
  pass 
  to 
  the 
  consideration 
  of 
  the 
  work 
  that 
  has 
  been 
  

   done 
  along 
  theoretical 
  lines 
  in 
  the 
  finding 
  out 
  of 
  relations 
  

   between 
  heat 
  of 
  vaporization, 
  temperature, 
  and 
  pressure. 
  

  

  The 
  first 
  effort 
  made 
  in 
  this 
  direction 
  is 
  due 
  to 
  Raoul 
  Pictet, 
  

   in 
  a 
  paper 
  truly 
  remarkable 
  for 
  its 
  time, 
  although 
  it 
  seems 
  to 
  

   have 
  attracted 
  but 
  little 
  attention. 
  Pictet 
  considers 
  a 
  cycle 
  in 
  

   which 
  a 
  liquid 
  is 
  evaporated 
  from 
  one 
  chamber, 
  condensed 
  in 
  

   another, 
  and 
  finally 
  returned 
  to 
  the 
  first. 
  Admitting 
  the 
  

   validity 
  for 
  the 
  case 
  in 
  hand 
  of 
  the 
  laws 
  of 
  Boyle 
  and 
  Gay- 
  

   Lussac, 
  he 
  then 
  finds 
  mathematical 
  expressions 
  for 
  the 
  work 
  

   done 
  and 
  the 
  heat 
  absorbed. 
  In 
  order 
  to 
  equate 
  these 
  essen- 
  

  

  *Com.ptes 
  Rend., 
  xxiii, 
  524, 
  1846. 
  

   f 
  Phil. 
  Mag., 
  V., 
  xviii, 
  54, 
  1884. 
  

  

  

  