﻿Equilibrium 
  of 
  Heterogeneous 
  Substances. 
  819 
  

  

  (such 
  as 
  the 
  potentials 
  of 
  Gibbs) 
  is, 
  it 
  would 
  seem, 
  here 
  set 
  

   forth 
  formally 
  and 
  explicitly 
  for 
  the 
  first 
  time, 
  though 
  it 
  is 
  

   ■thoroughly 
  implied 
  throughout 
  Gibbs's 
  work. 
  This 
  paper 
  

   reviews 
  only 
  the 
  first 
  portion 
  of 
  that 
  work, 
  Proc. 
  Con- 
  

   necticut 
  Academy, 
  Oct. 
  1875-May 
  1876 
  ; 
  the 
  second 
  part 
  of 
  

   it, 
  mainly 
  special 
  applications, 
  did 
  not 
  appear 
  in 
  the 
  same 
  

   Proceedings 
  until 
  May 
  18 
  7 
  7- 
  July 
  1878. 
  The 
  principle, 
  

   as 
  restated 
  in 
  less 
  guarded 
  terms 
  by 
  G. 
  Helm 
  (1887), 
  that 
  

   •each 
  type 
  of 
  (available) 
  energy 
  strives 
  to 
  pass 
  from 
  positions 
  

   of 
  higher 
  to 
  positions 
  of 
  lower 
  intensity, 
  has 
  been 
  supposed 
  

   sometimes 
  to 
  mark 
  a 
  new 
  departure 
  in 
  physical 
  ideas 
  : 
  

   cf. 
  Prof. 
  W. 
  Ostwald, 
  Die 
  Energie 
  (1908) 
  p. 
  103, 
  whose 
  

   regret, 
  expressed 
  in 
  this 
  connexion, 
  that 
  he 
  has 
  not 
  had 
  

   access 
  to 
  Maxwell's 
  paper, 
  has 
  revived 
  the 
  project 
  of 
  re- 
  

   printing 
  it. 
  Some 
  years 
  before 
  this 
  time, 
  in 
  a 
  paper 
  " 
  On 
  

   the 
  Mathematical 
  Classification 
  of 
  Physical 
  Quantities," 
  Proc. 
  

   Lond. 
  Math. 
  Soc. 
  vol. 
  iii., 
  Maxwell 
  had 
  pointed 
  out, 
  in 
  

   connexion 
  with 
  Rankine's 
  idea 
  of 
  factors 
  of 
  energy, 
  that 
  

   this 
  conception 
  loses 
  most 
  of 
  its 
  definiteness 
  and 
  efficacy 
  

   when 
  applied 
  to 
  kinetic 
  phenomena. 
  It 
  is 
  only 
  for 
  static 
  or 
  

   steady 
  material 
  transformations 
  that 
  it 
  is 
  effective 
  ; 
  and 
  it 
  

   became 
  so, 
  in 
  development 
  of 
  the 
  general 
  Kelvin 
  doctrine 
  

   of 
  available 
  energy, 
  only 
  by 
  virtue 
  of 
  the 
  fundamental 
  step 
  

   involved 
  in 
  Gibbs' 
  s 
  recognition 
  of 
  the 
  existence 
  of 
  quanti- 
  

   tative 
  chemical 
  potentials 
  for 
  the 
  independent 
  constituent 
  

   substances 
  of 
  a 
  mixture 
  or 
  solution, 
  — 
  involving 
  the 
  formu- 
  

   lation 
  of 
  the 
  general 
  criterion 
  of 
  chemical 
  coexistence 
  of 
  

   complex 
  substances 
  in 
  contact, 
  that 
  the 
  potential 
  of 
  each 
  

   constituent 
  should 
  be 
  the 
  same 
  in 
  both 
  of 
  them, 
  and 
  of 
  the 
  

   trend 
  of 
  chemical 
  change, 
  towards 
  positions 
  of 
  lower 
  aggregate 
  

   potential. 
  

  

  Most 
  interesting 
  also 
  as 
  regards 
  this 
  evolution 
  of 
  ideas 
  is 
  

   the 
  postscript 
  of 
  a 
  letter 
  from 
  Maxwell 
  to 
  Stokes 
  of 
  an 
  

   earlier 
  date, 
  August 
  3, 
  1875, 
  in 
  which, 
  in 
  connexion 
  with 
  

   Andrews's 
  experiments 
  on 
  the 
  condensation 
  of 
  mixed 
  gases, 
  

   Maxwell 
  sends 
  a 
  tentative 
  sketch 
  of 
  the 
  whole 
  theory, 
  

   using 
  a 
  provisional 
  term 
  reaction, 
  printed 
  between 
  inverted 
  

   commas, 
  for 
  the 
  quantity 
  which 
  his 
  friend 
  Gibbs 
  soon 
  after- 
  

   wards 
  named 
  chemical 
  potential 
  : 
  see 
  ' 
  Memoir 
  and 
  Scientific 
  

   Correspondence 
  of 
  Sir 
  G. 
  G. 
  Stokes,' 
  vol. 
  ii. 
  pp. 
  33-35 
  

   (Cambridge, 
  1907). 
  — 
  J. 
  Larmor.] 
  

  

  THE 
  warning 
  which 
  Comte 
  addressed 
  to 
  his 
  disciples, 
  

   not 
  to 
  apply 
  dynamical 
  or 
  physical 
  ideas 
  to 
  chemical 
  

   phenomena, 
  may 
  be 
  taken, 
  like 
  several 
  other 
  warnings 
  of 
  

   his, 
  as 
  an 
  indication 
  of 
  the 
  direction 
  in 
  which 
  science 
  was 
  

   threatening 
  to 
  advance. 
  

  

  3H2 
  

  

  