﻿622 
  Prof. 
  Kuerten 
  and 
  Mr. 
  Robson 
  on 
  the 
  Thermal 
  

  

  Selenium 
  shows 
  a 
  strong 
  surface-colour 
  if 
  the 
  angle 
  of 
  

   incidence 
  is 
  in 
  the 
  neighbourhood 
  of 
  the 
  polarizing 
  angle, 
  and 
  

   the 
  reflected 
  light 
  is 
  examined 
  through 
  a 
  nicol 
  turned 
  so 
  as 
  

   to 
  extinguish 
  as 
  much 
  as 
  possible 
  of 
  the 
  reflected 
  light. 
  The 
  

   colour 
  ranges 
  from 
  a 
  greenish 
  white 
  through 
  blue 
  to 
  deep 
  

   violet 
  as 
  the 
  angle 
  of 
  incidence 
  increases. 
  

  

  The 
  elliptical 
  polarization 
  of 
  light 
  reflected 
  from 
  selenium 
  

   and 
  the 
  determination 
  of 
  the 
  absorption 
  and 
  dispersion 
  curves 
  

   by 
  the 
  katoptric 
  method 
  is 
  now 
  in 
  progress, 
  as 
  well 
  as 
  an 
  

   investigation 
  of 
  the 
  behaviour 
  of 
  the 
  substance 
  in 
  the 
  infra-red. 
  

   It 
  will 
  be 
  interesting 
  to 
  compare 
  the 
  results 
  obtained 
  in 
  this 
  

   way 
  with 
  the 
  results 
  obtained 
  by 
  the 
  dioptric 
  method. 
  

  

  The 
  refraction 
  and 
  extinction 
  curves 
  for 
  selenium, 
  ob- 
  

   tained 
  by 
  the 
  katoptric 
  method, 
  are 
  given 
  in 
  Ketteler's 
  

   'Theoretical 
  Optics/ 
  p. 
  552; 
  but 
  it 
  is 
  not 
  stated 
  whether 
  

   the 
  experiments 
  were 
  made 
  with 
  the 
  glassy 
  or 
  metallic 
  

   modification. 
  The 
  refraction 
  curve 
  in 
  the 
  red 
  and 
  orange 
  

   region 
  is 
  obviously 
  wrong, 
  if 
  it 
  is 
  intended 
  to 
  represent 
  the 
  

   dispersion 
  of 
  the 
  glassy 
  modification, 
  as 
  can 
  be 
  seen 
  by 
  com- 
  

   paring 
  it 
  with 
  the 
  curve 
  obtained 
  with 
  the 
  prisms. 
  

  

  LXX. 
  The 
  'Thermal 
  Properties 
  of 
  Carbon 
  Dioxide 
  and 
  of 
  

   Ethane. 
  Bij 
  J. 
  P. 
  Kuenen 
  and 
  W. 
  G. 
  Kobson*. 
  

  

  I. 
  Caebon 
  Dioxide. 
  

  

  OUR 
  measurements 
  of 
  the 
  vapour-pressures 
  of 
  carbon 
  

   dioxide 
  communicated 
  in 
  a 
  recent 
  paper 
  | 
  make 
  it 
  

   possible 
  to 
  discuss 
  the 
  thermal 
  properties 
  of 
  this 
  substance 
  

   within 
  wider 
  limits 
  than 
  could 
  be 
  done 
  hitherto. 
  By 
  our 
  

   results, 
  together 
  with 
  those 
  of 
  Amagat 
  if, 
  the 
  vapour-pressures 
  

   of 
  the 
  liquid 
  are 
  known 
  between 
  the 
  critical 
  temperature 
  and 
  

   — 
  65° 
  C, 
  and 
  the 
  vapour-pressures 
  of 
  the 
  solid 
  from 
  the 
  

   triple 
  point 
  downwards. 
  The 
  densities 
  of 
  the 
  coexisting 
  

   liquid 
  and 
  vapour 
  above 
  0° 
  (J. 
  have 
  been 
  determined 
  by 
  

   Amagat 
  ; 
  and 
  below 
  0° 
  C. 
  there 
  is 
  a 
  recent 
  determination 
  of 
  

   the 
  liquid 
  densities 
  down 
  to 
  — 
  60° 
  0. 
  by 
  Behn§. 
  Behn 
  has 
  

   also 
  measured 
  the 
  density 
  of 
  the 
  solid 
  at 
  the 
  boiling-point. 
  

   Mathias 
  || 
  has 
  determined 
  the 
  latent 
  heat 
  of 
  evaporation 
  above 
  

   0° 
  C. 
  up 
  to 
  the 
  critical 
  point, 
  while 
  BehnU 
  obtained 
  the 
  latent 
  

   heat 
  of 
  sublimation 
  at 
  the 
  boiling-point 
  —78° 
  C. 
  

  

  * 
  Communicated 
  by 
  the 
  Authors. 
  

  

  + 
  Kuenen 
  and 
  Robson, 
  Phil. 
  Mag. 
  [8] 
  iii. 
  p. 
  149. 
  

  

  | 
  Amagat, 
  Ann. 
  Phys. 
  Chimie 
  [6] 
  xxix. 
  p. 
  130. 
  

  

  § 
  Behn, 
  Ann. 
  der 
  Physik, 
  iii. 
  p. 
  733. 
  

  

  !! 
  Mathias, 
  Theses 
  a 
  la 
  Facnlte 
  des 
  8c. 
  de 
  Paris, 
  No. 
  C87, 
  1890. 
  

  

  % 
  Behn, 
  Ann. 
  der 
  PhystJc. 
  i. 
  p. 
  270. 
  

  

  