﻿420 
  Lord 
  Rayleigh 
  on 
  the 
  Question 
  of 
  

  

  agent. 
  Taking 
  into 
  account 
  the 
  slower 
  rate 
  of 
  passage 
  in 
  

   litres 
  per 
  hour, 
  it 
  would 
  seem 
  that 
  my 
  arrangement 
  had 
  the 
  

   advantage 
  in 
  this 
  respect. 
  

  

  An 
  attempt 
  w 
  T 
  as 
  made 
  to 
  improve 
  the 
  phosphoric 
  anhydride 
  

   by 
  a 
  preliminary 
  heating 
  for 
  many 
  hours 
  to 
  260° 
  in 
  a 
  current 
  

   of 
  dry 
  air, 
  somewhat 
  as 
  recommended 
  by 
  M. 
  Gautier, 
  but 
  the 
  

   results 
  were 
  not 
  appreciably 
  altered. 
  When 
  one 
  remembers 
  

   the 
  experiments 
  of 
  Baker, 
  from 
  which 
  it 
  appears 
  that, 
  if 
  all 
  

   is 
  thoroughly 
  dry, 
  heated 
  phosphorus 
  does 
  not 
  combine 
  with 
  

   oxygen, 
  it 
  is 
  difficult 
  to 
  feel 
  confidence 
  in 
  this 
  process. 
  

  

  It 
  was 
  certain 
  that 
  the 
  sample 
  of 
  phosphoric 
  anhydride 
  

   hitherto 
  employed 
  in 
  this 
  work 
  was 
  inferior. 
  When 
  a 
  tube 
  

   o£ 
  it 
  which 
  had 
  been 
  used 
  for 
  some 
  time 
  (in 
  other 
  work) 
  and 
  

   had 
  become 
  gummy 
  at 
  the 
  ends, 
  was 
  strongly 
  heated 
  over 
  a 
  

   spirit 
  flame, 
  occasional 
  flashes 
  could 
  be 
  seen 
  in 
  the 
  dark. 
  

   Treatment 
  in 
  the 
  cold 
  with 
  ozonized 
  air 
  seemed 
  to 
  effect 
  an 
  

   improvement 
  ; 
  but 
  experiments 
  in 
  this 
  direction 
  were 
  not 
  

   pursued 
  to 
  a 
  definite 
  conclusion 
  in 
  consequence 
  of 
  the 
  dis- 
  

   covery 
  that 
  when 
  another 
  sample 
  of 
  phosphoric 
  anhydride 
  

   was 
  substituted 
  for 
  that 
  hitherto 
  in 
  use 
  the 
  anomaly 
  disap- 
  

   peared. 
  Thus 
  in 
  four 
  trials 
  where 
  10 
  litres 
  of 
  air 
  were 
  

   passed 
  without 
  a 
  furnace, 
  the 
  gains 
  were 
  

  

  Nov. 
  26, 
  1901 
  

  

  ii 
  30, 
  ,, 
  

   Dec. 
  2, 
  „ 
  

  

  —•00016 
  

   -•00003 
  

   + 
  •00014 
  

  

  + 
  •00006 
  

  

  Mean 
  .... 
  -00000 
  

  

  thus 
  on 
  the 
  whole 
  no 
  gain 
  of 
  weight. 
  The 
  errors 
  would 
  

   appear 
  somewhat 
  to 
  exceed 
  *1 
  mg., 
  but 
  it 
  may 
  be 
  noted 
  that 
  

   in 
  this 
  and 
  following 
  tables 
  the 
  real 
  error 
  is 
  liable 
  to 
  appear 
  

   exaggerated. 
  If 
  in 
  consequence 
  of 
  an 
  error 
  of 
  weighing, 
  or 
  

   of 
  allowance 
  for 
  weight 
  of 
  included 
  air, 
  or 
  of 
  a 
  varied 
  con- 
  

   dition 
  of 
  the 
  outer 
  surface 
  of 
  the 
  tube, 
  a 
  recorded 
  gain 
  is 
  too 
  

   high, 
  the 
  next 
  is 
  likely 
  to 
  appear 
  too 
  low. 
  

  

  In 
  the 
  operations 
  which 
  followed, 
  the 
  furnace-tube 
  was 
  

   charged 
  with 
  copper 
  oxide 
  prepared 
  in 
  situ 
  by 
  oxidation 
  of 
  

   small 
  pieces 
  of 
  thin 
  copper 
  foil 
  with 
  which 
  the 
  tube 
  was 
  

   packed. 
  Examination 
  once 
  or 
  twice 
  after 
  a 
  breakage 
  showed 
  

   that 
  the 
  oxidation 
  was 
  not 
  complete, 
  but 
  no 
  measurements 
  

   were 
  taken 
  until 
  there 
  was 
  no 
  appreciable 
  further 
  absorption 
  

   of 
  oxygen. 
  After 
  the 
  copper 
  oxide 
  has 
  been 
  exposed 
  to 
  the 
  

   air 
  of 
  the 
  room, 
  many 
  hours' 
  heating 
  to 
  redness 
  in 
  a 
  current 
  

   of 
  dry 
  air 
  are 
  required 
  to 
  remove 
  the 
  adherent 
  moisture. 
  

  

  