﻿614 
  Mr. 
  J. 
  Satterly 
  on 
  the 
  Amount 
  oj 
  

  

  method 
  are 
  the 
  accumulation 
  of 
  emanation 
  by 
  the 
  charcoal 
  

   and 
  the 
  tediousness 
  of 
  the 
  heating 
  and 
  collecting 
  processes. 
  

   On 
  the 
  other 
  hand, 
  the 
  condenser 
  method 
  consumes 
  a 
  large 
  

   quantity 
  of 
  liquid 
  air 
  and 
  could 
  only 
  be 
  used 
  in 
  laboratories 
  

   where 
  there 
  is 
  a 
  good 
  supply 
  of 
  this 
  valuable 
  commodity. 
  

  

  How 
  much 
  of 
  the 
  Natural 
  Ionization 
  of 
  the 
  Atmosphere 
  

   is 
  due 
  to 
  the 
  Radium 
  Emanation 
  present 
  ? 
  

  

  Rutherford* 
  states 
  that 
  the 
  total 
  number 
  of 
  a-particles 
  

   projected 
  per 
  second 
  by 
  one 
  gram 
  of 
  radium 
  and 
  its 
  dis- 
  

   integration 
  products 
  in 
  radioactive 
  equilibrium 
  is 
  2*5 
  x 
  10 
  11 
  . 
  

   Radium, 
  radium 
  emanation, 
  radium, 
  A 
  and 
  radium 
  C 
  are 
  

   equally 
  responsible 
  for 
  this 
  output 
  of 
  a-particles, 
  hence 
  it 
  

   follows 
  that 
  the 
  amounts 
  of 
  emanation, 
  radium 
  A, 
  and 
  

   radium 
  C 
  in 
  radioactive 
  equilibrium 
  with 
  one 
  gram 
  of 
  radium 
  

   project 
  1*9 
  x 
  10 
  11 
  a-particles 
  per 
  sec. 
  

  

  It 
  is 
  now 
  necessary 
  to 
  find 
  the 
  number 
  of 
  ions 
  produced 
  

   in 
  a 
  gas 
  by 
  these 
  a-particles. 
  An 
  a-particle 
  from 
  radium 
  

   itself 
  produces 
  86000 
  ions 
  in 
  a 
  gas 
  before 
  it 
  is 
  absorbed 
  f. 
  

   On 
  the 
  assumption 
  X 
  that 
  the 
  number 
  of 
  ions 
  produced 
  

   by 
  an 
  a-particle 
  from 
  any 
  product 
  is 
  proportional 
  to 
  the 
  

   energy 
  lost 
  by 
  that 
  particle 
  before 
  it 
  reaches 
  its 
  critical 
  

   velocity 
  § 
  it 
  follows 
  that 
  a-particles 
  from 
  radium 
  emanation, 
  

   radium 
  A, 
  and 
  radium 
  C 
  produce 
  106,000, 
  110,000, 
  and 
  

   172,000 
  ions 
  respectively 
  before 
  they 
  are 
  absorbed, 
  or 
  an 
  

   average 
  of 
  130,000. 
  

  

  In 
  comparison 
  with 
  the 
  ionization 
  produced 
  by 
  the 
  

   a 
  particles, 
  the 
  ionization 
  produced 
  by 
  the 
  /3 
  particles 
  and 
  

   7 
  rays 
  from 
  the 
  three 
  products 
  considered 
  may 
  be 
  neglected. 
  

  

  The 
  number 
  of 
  ions 
  produced 
  per 
  sec. 
  per 
  cub. 
  metre 
  of 
  air 
  

   by 
  the 
  emanation, 
  radium 
  A, 
  and 
  radium 
  C 
  in 
  radioactive 
  

   equilibrium 
  with 
  100 
  x 
  10~ 
  12 
  grm. 
  of 
  radium 
  is 
  therefore 
  

  

  (100 
  x 
  lO" 
  12 
  ) 
  x 
  (1-9 
  x 
  10 
  n 
  ) 
  x 
  (1-3 
  x 
  10 
  5 
  ; 
  or 
  2*5 
  x 
  10 
  6 
  , 
  

  

  or 
  about 
  three 
  per 
  c.c. 
  per 
  sec. 
  

  

  The 
  number 
  of 
  ions 
  actually 
  produced 
  in 
  the 
  air 
  per 
  c.c. 
  

   per 
  sec. 
  is 
  subject 
  to 
  great 
  variation. 
  Rutherford 
  || 
  states 
  

   the 
  number 
  in 
  the 
  open 
  air 
  to 
  be 
  30 
  ; 
  Schuster 
  % 
  found 
  it 
  to 
  

  

  * 
  Rutherford, 
  ' 
  Radioactivity/ 
  2nd 
  edition, 
  p. 
  155. 
  

   t 
  Ibid. 
  p. 
  433. 
  " 
  % 
  Ibid. 
  p. 
  549. 
  

  

  § 
  Ibid. 
  p. 
  547 
  j 
  and 
  Phil. 
  Mag. 
  Jan. 
  1907. 
  

   {{ 
  Rutherford, 
  ' 
  Radioactivity/ 
  2nd 
  edition, 
  p. 
  526. 
  

   ^ 
  Schuster, 
  Proc. 
  Manchester 
  Phil. 
  Soc. 
  1904. 
  

  

  