﻿Radium 
  Emanation 
  in 
  the 
  Atmosphere. 
  605 
  

  

  since 
  the 
  length 
  of 
  the 
  tubes 
  of 
  the 
  condenser 
  is 
  16 
  cms. 
  

  

  the 
  air 
  spends 
  two 
  seconds 
  in 
  going 
  through 
  the 
  tubes 
  of 
  the 
  

  

  condenser, 
  and 
  to 
  this 
  may 
  be 
  added 
  a 
  little 
  more, 
  due 
  to 
  the 
  

  

  stem 
  of 
  the 
  condenser. 
  So 
  that 
  the 
  condenser 
  has 
  two 
  seconds 
  

  

  in 
  which 
  to 
  reduce 
  the 
  temperature 
  of 
  the 
  air 
  from 
  15° 
  C, 
  

  

  say, 
  to 
  —150° 
  C. 
  If 
  we 
  assume 
  that 
  the 
  tubes 
  are 
  as 
  closely 
  

  

  packed 
  as 
  possible 
  the 
  greatest 
  distance 
  a 
  particle 
  of 
  air 
  could 
  

  

  be 
  from 
  the 
  cold 
  metal 
  = 
  *1 
  85/^/3 
  "cm. 
  or 
  1 
  mm. 
  Of 
  course 
  

  

  if 
  the 
  packing 
  is 
  irregular 
  there 
  will 
  be 
  some 
  tubes 
  much 
  

  

  larger 
  than 
  the 
  others, 
  and 
  most 
  of 
  the 
  air 
  will 
  go 
  through 
  

  

  these 
  large 
  tubes. 
  

  

  The 
  mass 
  of 
  the 
  condenser 
  was 
  713 
  grms., 
  of 
  which, 
  say 
  

  

  700 
  grms. 
  fell 
  to 
  the 
  temperature 
  of 
  liquid 
  air. 
  To 
  cool 
  it 
  

  

  from 
  ordinary 
  temperature 
  to 
  the 
  temperature 
  of 
  liquid 
  air 
  

  

  700 
  x 
  '095 
  x 
  200 
  calories 
  of 
  heat 
  must 
  be 
  abstracted. 
  The 
  

  

  latent 
  heat 
  of 
  vaporisation 
  of 
  air 
  is 
  55 
  calories 
  per 
  grin. 
  

  

  700 
  x 
  -095x200 
  ■ 
  , 
  ,. 
  .. 
  . 
  

  

  Hence 
  ^ 
  or 
  21o 
  grms. 
  or 
  liquid 
  air 
  are 
  used 
  

  

  up 
  in 
  reducing 
  it 
  to 
  the 
  temperature 
  of 
  liquid 
  air. 
  The 
  air 
  

   passing 
  through 
  the 
  condenser 
  also 
  gives 
  out 
  heat. 
  The 
  

   amount 
  of 
  liquid 
  air 
  boiled 
  away 
  by 
  a 
  stream 
  of 
  air 
  flowing 
  

   at 
  the 
  rate 
  of 
  i 
  litre 
  per 
  minute 
  for 
  two 
  hours, 
  

  

  60 
  x 
  1'3 
  x 
  -238x200 
  ^ 
  

  

  = 
  =•= 
  = 
  bo 
  grms. 
  

  

  It 
  was 
  also 
  calculated 
  that 
  130 
  grms. 
  would 
  be 
  required 
  to 
  

   supply 
  the 
  heat 
  conducted 
  down 
  the 
  stem 
  of 
  the 
  condenser 
  in 
  

   two 
  hours. 
  This 
  gives 
  a 
  total 
  of 
  150 
  grms. 
  of 
  liquid 
  air 
  

   required 
  for 
  a 
  2 
  hours' 
  experiment. 
  As 
  a 
  matter 
  of 
  fact 
  I 
  

   usually 
  required 
  J 
  litre 
  for 
  a 
  3 
  hours' 
  experiment. 
  

  

  Method 
  of 
  conducting 
  an 
  Experiment. 
  

  

  The 
  apparatus 
  used 
  was 
  the 
  same 
  as 
  before 
  except, 
  of 
  

   course, 
  that 
  no 
  charcoal 
  tubes, 
  furnace, 
  or 
  aspirators 
  were 
  

   required. 
  

  

  The 
  stem 
  of 
  the 
  condenser 
  was 
  covered 
  with 
  cotton-wool 
  

   and 
  supported 
  by 
  a 
  clamp 
  so 
  that 
  the 
  condenser 
  could 
  be 
  

   placed 
  well 
  into 
  the 
  interior 
  of 
  a 
  cylindrical 
  Dewar's 
  tube 
  

   about 
  4 
  cms. 
  in 
  internal 
  diameter 
  and 
  28 
  cms. 
  deep 
  

   internally. 
  

  

  In 
  beginning 
  an 
  experiment 
  the 
  Dewar 
  tube 
  was 
  about 
  

   two-thirds 
  filled 
  with 
  liquid 
  air 
  and 
  the 
  condenser 
  gradually 
  

  

  