﻿NOV. 
  4, 
  1922 
  COBLENTZ: 
  THERMAL 
  RADIANT 
  ENERGY 
  411 
  

  

  therefore, 
  we 
  may, 
  if 
  we 
  like, 
  regard 
  the 
  rise 
  in 
  temperature 
  during 
  

   extrusion 
  as 
  being 
  (nearly) 
  that 
  due 
  to 
  the 
  conversion 
  of 
  the 
  work 
  

   expended 
  on 
  them 
  into 
  heat, 
  this 
  conversion 
  being 
  effected 
  by 
  friction 
  

   along 
  the 
  walls 
  or 
  by 
  internal 
  friction 
  (viscosity) 
  ; 
  but 
  for 
  gases, 
  of 
  

   course, 
  this 
  is 
  not 
  even 
  approximately 
  true. 
  

  

  It 
  is 
  of 
  interest 
  in 
  this 
  connection 
  to 
  note 
  the 
  behavior 
  of 
  antimony 
  

   when 
  extruded 
  through 
  a 
  small 
  opening. 
  According 
  to 
  Bridgman 
  

   the 
  extrusion 
  at 
  certain 
  pressures 
  proceeds 
  slowly 
  and 
  ;-egularly, 
  but 
  

   if 
  the 
  pressure 
  is 
  raised 
  to 
  a 
  certain 
  critical 
  value, 
  the 
  antimony 
  comes 
  

   out 
  with 
  almost 
  explosive 
  violence 
  and 
  in 
  the 
  form 
  of 
  a 
  long, 
  con- 
  

   tinuous 
  wire. 
  Now 
  the 
  temperature 
  rise 
  for 
  isenkaumic 
  expansion 
  

   of 
  antimony 
  is 
  about 
  the 
  same 
  as 
  for 
  lead, 
  namely 
  about 
  70° 
  per 
  

   1000 
  megabars. 
  Since 
  the 
  pressure 
  was 
  10,000 
  megabars 
  or 
  more, 
  the 
  

   question 
  may 
  well 
  be 
  raised 
  as 
  to 
  whether 
  the 
  antimony, 
  in 
  spite 
  of 
  

   heat 
  losses, 
  may 
  not 
  have 
  been 
  raised 
  to 
  its 
  melting 
  point 
  at 
  ordinary 
  

   pressure, 
  namely, 
  630° 
  C. 
  

  

  PHYSICS. 
  — 
  Some 
  observations 
  on 
  the 
  transformation 
  of 
  thermal 
  radiant 
  

   energy 
  into 
  electric 
  current 
  in 
  molybdenite 
  ^ 
  W. 
  W. 
  CoblEntz, 
  

   Bureau 
  of 
  Standards. 
  

  

  As 
  announced 
  in 
  the 
  Bureau 
  of 
  Standards 
  Tech. 
  News 
  Bulletin, 
  

   No. 
  61 
  of 
  May 
  11, 
  1922, 
  during 
  the 
  past 
  year 
  the 
  writer 
  has 
  been 
  

   searching 
  for 
  a 
  possible 
  relation 
  between 
  (1) 
  an 
  e.m.f 
  . 
  which 
  is 
  observed 
  

   in 
  isolated 
  spots 
  in 
  certain 
  samples 
  of 
  molybdenite 
  when 
  exposed 
  to 
  

   thermal 
  radiation 
  but 
  without 
  an 
  impressed 
  e.m.f., 
  and 
  (2) 
  the 
  photo- 
  

   electrical 
  reaction 
  (which 
  is 
  usually 
  considered 
  a 
  change 
  in 
  resistance) 
  

   exhibited 
  in 
  these 
  same 
  spots 
  when 
  subjected 
  to 
  an 
  impressed 
  e.m.f. 
  and 
  

   exposed 
  to 
  thermal 
  radiation. 
  

  

  The 
  materials 
  examined 
  are 
  narrow 
  strips 
  of 
  molybdenite 
  1 
  to 
  6 
  

   cm. 
  in 
  length, 
  soldered 
  to 
  copper 
  wires 
  which 
  are 
  connected 
  with 
  a 
  

   Thomson 
  galvanometer. 
  

  

  Touching 
  the 
  copper-molybdenite 
  junctures 
  with 
  a 
  thin 
  hot 
  wire 
  

   produces 
  the 
  well 
  known 
  thermal 
  e.m.f. 
  of 
  a 
  heterogeneous 
  circuit. 
  

   Touching 
  the 
  intervening 
  parts 
  of 
  the 
  crystal 
  with 
  the 
  hot 
  wire 
  pro- 
  

   duces 
  no 
  e.m.fs. 
  

  

  On 
  the 
  other 
  hand, 
  focusing 
  the 
  short 
  wave-length 
  radiations 
  from 
  

   a 
  Nernst 
  glower 
  or 
  tungsten-ribbon 
  lamp 
  upon 
  different 
  parts 
  of 
  the 
  

  

  » 
  Received 
  September 
  16, 
  1922. 
  

  

  