﻿L 
  622 
  ] 
  

  

  LI. 
  On 
  the 
  Amount 
  of 
  Radium 
  Emanation 
  in 
  the 
  Atmosphere 
  

   near 
  the 
  Eartlis 
  Surface. 
  By 
  A. 
  S. 
  Eve, 
  D.Sc, 
  Associate 
  

   Professor 
  of 
  Mathematics, 
  McGill 
  University, 
  Montreal* 
  . 
  

  

  IN 
  a 
  previous 
  paper 
  published 
  in 
  this 
  Magazine 
  (December 
  

   1907) 
  a 
  preliminary 
  account 
  was 
  given 
  o£ 
  determina- 
  

   tions 
  of 
  the 
  amount 
  of 
  radium 
  emanation 
  present 
  in 
  the 
  

   atmosphere. 
  In 
  the 
  present 
  communication 
  the 
  results 
  are 
  

   given 
  of 
  experiments, 
  continued 
  at 
  intervals 
  throughout 
  a 
  

   year, 
  which 
  not 
  only 
  determine 
  the 
  amount 
  with 
  greater 
  

   accuracy, 
  but 
  also 
  throw 
  some 
  light 
  on 
  the 
  effect 
  of 
  meteoro- 
  

   logical 
  conditions 
  in 
  causing 
  variations 
  in 
  that 
  amount. 
  

  

  In 
  order 
  to 
  save 
  reference 
  a 
  brief 
  summary 
  of 
  the 
  previous 
  

   paper 
  is 
  here 
  given. 
  The 
  experiments 
  were 
  made 
  at 
  

   Montreal, 
  in 
  the 
  Chemistry 
  Building 
  of 
  McGill 
  University, 
  

   in 
  a 
  room 
  about 
  fifty 
  feet 
  above 
  the 
  ground. 
  The 
  air, 
  drawn 
  

   from 
  outside 
  through 
  cotton-wool, 
  was 
  passed 
  through 
  three 
  

   glass 
  tubes 
  containing 
  charcoal 
  prepared 
  from 
  the 
  shells 
  of 
  

   coconuts. 
  The 
  air-current 
  was 
  continued 
  for 
  2*7 
  days, 
  at 
  a 
  

   speed 
  of 
  6*7 
  cm. 
  3 
  /sec, 
  so 
  that 
  1*56 
  m. 
  3 
  of 
  air 
  passed 
  through 
  

   the 
  tubes, 
  two 
  of 
  which 
  were 
  in 
  parallel 
  f 
  and 
  the 
  third 
  in 
  

   series 
  with 
  them. 
  The 
  tubes 
  were 
  then 
  successively 
  heated 
  

   over 
  two 
  Bunsen 
  flames, 
  so 
  that 
  the 
  gases 
  absorbed 
  by 
  the 
  

   charcoal 
  were 
  expelled, 
  and 
  these 
  were 
  collected 
  over 
  water 
  

   and 
  introduced 
  into 
  a 
  silvered 
  glass 
  electroscope, 
  which 
  had 
  

   previously 
  been 
  partially 
  exhausted 
  by 
  a 
  filter 
  pump. 
  The 
  

   movements 
  of 
  the 
  leaf 
  of 
  the 
  electroscope 
  were 
  measured 
  in 
  

   the 
  usual 
  way 
  with 
  a 
  microscope. 
  

  

  A 
  solution 
  of 
  radium 
  bromide, 
  containing 
  1*57 
  x 
  10 
  _9 
  gram 
  

   of 
  pure 
  radium, 
  taken 
  from 
  a 
  standard 
  solution 
  prepared 
  by 
  

   BoltwoodJ, 
  Levin, 
  and 
  the 
  writer, 
  was 
  then 
  introduced 
  into 
  

   a 
  flask. 
  Air 
  was 
  bubbled 
  through 
  this 
  solution, 
  dried 
  by 
  

   passing 
  through 
  two 
  flasks 
  of 
  concentrated 
  sulphuric 
  acid, 
  

   and 
  passed 
  at 
  the 
  same 
  rate 
  for 
  the 
  same 
  time 
  and 
  through 
  

   the 
  same 
  charcoal 
  as 
  before. 
  The 
  tubes 
  were 
  heated, 
  and 
  

   the 
  freed 
  gases 
  were 
  collected 
  and 
  tested 
  for 
  radium 
  emana- 
  

   tion. 
  It 
  was 
  found 
  that, 
  at 
  the 
  above-named 
  speed, 
  about 
  

   twenty 
  per 
  cent, 
  of 
  the 
  emanation 
  given 
  off 
  by 
  the 
  solution 
  

   was 
  in 
  this 
  manner 
  introduced 
  into 
  the 
  electroscope. 
  This 
  

   percentage 
  was 
  found 
  to 
  be 
  a 
  function 
  of 
  the 
  speed 
  of 
  the 
  

   air-current, 
  but 
  within 
  wide 
  limits 
  it 
  appeared 
  to 
  be 
  inde- 
  

  

  * 
  Communicated 
  by 
  tlie 
  Author. 
  

  

  t 
  It 
  is 
  better 
  not 
  to 
  place 
  tubes 
  in 
  parallel 
  as 
  the 
  resistances 
  to 
  the 
  

   air-current 
  are 
  often 
  unequal 
  and 
  inconstant. 
  

  

  X 
  American 
  Journal 
  of 
  Science, 
  vol. 
  xxii. 
  July 
  1906. 
  

  

  