﻿408 
  JOURNAL 
  OP 
  THE 
  WASHINGTON 
  ACADEMY 
  OF 
  SCIENCES 
  VOIv. 
  12, 
  NO. 
  18 
  

  

  . 
  . 
  bT 
  

  

  the 
  equation 
  is 
  written 
  — 
  — 
  for 
  convenience 
  in 
  representing 
  the 
  

  

  op 
  

  

  rise 
  in 
  temperature 
  due 
  to 
  decrease 
  of 
  pressure. 
  

  

  (B) 
  Explosive 
  release 
  of 
  pressure. 
  Isenergic 
  expansion.—When 
  

   pressure 
  on 
  a 
  given 
  amount 
  of 
  material 
  is 
  released 
  in 
  such 
  a 
  way 
  that 
  

   no 
  heat 
  is 
  added 
  to 
  or 
  taken 
  away 
  from 
  the 
  material 
  and 
  no 
  work 
  is 
  

   done 
  on 
  or 
  by 
  the 
  surroundings, 
  the 
  intrinsic 
  energy 
  (E) 
  of 
  the 
  material 
  

   remains 
  constant, 
  and 
  the 
  expansion 
  may 
  be 
  termed 
  isenergic. 
  This 
  

   type 
  of 
  expansion 
  may 
  be 
  realized 
  by 
  allowing 
  a 
  gas 
  to 
  expand 
  from 
  

   one 
  part 
  of 
  a 
  container 
  to 
  another 
  (evacuated) 
  part, 
  or 
  — 
  of 
  more 
  

   practical 
  interest 
  — 
  ^by 
  the 
  sudden 
  release 
  of 
  pressure 
  on 
  a 
  liquid 
  

   contained 
  under 
  high 
  pressure 
  in 
  a 
  bomb, 
  e. 
  g., 
  by 
  a 
  breaking 
  of 
  the 
  

   walls 
  or 
  by 
  a 
  blowing 
  off 
  of 
  the 
  lid. 
  

  

  The 
  relation 
  between 
  temperature 
  and 
  pressure 
  in 
  isenergic 
  expan- 
  

   sion 
  is 
  : 
  

  

  ^p 
  — 
  aT 
  

  

  \dp/E 
  

  

  \dp 
  J 
  E 
  Cp 
  — 
  ap 
  

  

  (2) 
  

  

  /bv\ 
  

   jS 
  being 
  the 
  compressibility, 
  namely, 
  — 
  ( 
  :r- 
  ) 
  

  

  (C) 
  Porous 
  plug 
  release 
  of 
  pressure. 
  Isenkaumic 
  expansion. 
  — 
  

   The 
  third 
  variety 
  of 
  expansion 
  occurs 
  when 
  a 
  fluid 
  — 
  as 
  before, 
  insu- 
  

   lated 
  thermally 
  from 
  the 
  surroundings 
  — 
  reduces 
  its 
  pressure 
  by 
  stream- 
  

   ing 
  through 
  a 
  porous 
  plug 
  or 
  through 
  a 
  throttle 
  of 
  some 
  sort. 
  In 
  

   this 
  case 
  a 
  certain 
  thermodynamic 
  quantity, 
  represented 
  by 
  the 
  

   letter 
  H 
  and 
  commonly 
  called 
  heat 
  content, 
  remains 
  constant. 
  The 
  

   expression, 
  heat 
  content, 
  is 
  sometimes 
  confused 
  with 
  heat 
  capacity 
  

   and, 
  moreover, 
  the 
  two-word 
  name 
  does 
  not 
  lend 
  itself 
  well 
  to 
  the 
  

   formation 
  of 
  derivatives. 
  Thus, 
  "isoheatcontentic" 
  would 
  be 
  an 
  

   awkward 
  term. 
  For 
  these 
  reasons 
  a 
  single-word 
  equivalent 
  of 
  heat 
  

   content 
  would 
  be 
  desirable, 
  and 
  the 
  word 
  enkaumy^ 
  is 
  here 
  proposed. 
  

  

  In 
  the 
  process 
  just 
  considered 
  the 
  enkaumy 
  remains 
  constant, 
  and 
  

   for 
  this 
  isenkaumic 
  expansion 
  the 
  relation 
  between 
  temperature 
  and 
  

   pressure 
  is 
  : 
  

  

  '^^^ 
  ="-^^ 
  (3) 
  

  

  _/bT 
  

  

  bp/H 
  

  

  Cp 
  

  

  2 
  Greek, 
  Kavfia 
  from 
  Kautv 
  to 
  burn. 
  Cf. 
  obsolete 
  English 
  word, 
  cauma, 
  heat. 
  For 
  

   the 
  suggestion 
  of 
  this 
  root 
  I 
  wish 
  to 
  thank 
  my 
  colleague, 
  Dr. 
  Henry 
  S. 
  Washington. 
  

  

  It 
  is 
  of 
  interest 
  to 
  note 
  that 
  — 
  AH, 
  the 
  difference 
  in 
  enkaumy 
  of 
  two 
  states, 
  is 
  the 
  exact 
  

   equivalent 
  of 
  the 
  heat 
  of 
  combustion, 
  or 
  the 
  heat 
  of 
  reaction, 
  at 
  constant 
  pressure. 
  

  

  