﻿Molecular 
  Weights 
  of 
  Radioactive 
  Emanations. 
  949 
  

  

  steady 
  state 
  will 
  be 
  reached 
  when 
  the 
  number 
  passing 
  through 
  

   the 
  hole 
  per 
  second 
  is 
  equal 
  to 
  the 
  number 
  disintegrating 
  

   in 
  II. 
  Assuming 
  actinium 
  emanation 
  to 
  be 
  monatomic 
  and 
  

   to 
  have 
  a 
  disintegration 
  constant 
  X, 
  we 
  have 
  

  

  inA(N 
  l 
  -N 
  2 
  )=\N 
  2 
  V 
  2 
  

  

  (1) 
  

  

  The 
  ratio 
  N^^ 
  can 
  be 
  obtained 
  by 
  allowing 
  the 
  process 
  

   to 
  go 
  on 
  so 
  long 
  that 
  the 
  active 
  deposit 
  is 
  in 
  equilibrium 
  with 
  

   the 
  emanation 
  in 
  each 
  chamber, 
  so 
  that 
  on 
  removing 
  the 
  

   source 
  of 
  emanation 
  the 
  ratio 
  of 
  the 
  amounts 
  of 
  active 
  deposit 
  

   is 
  equal 
  to 
  the 
  ratio 
  of 
  the 
  numbers 
  o£ 
  emanation 
  atoms 
  

   initially 
  present. 
  In 
  this 
  way 
  ft 
  can 
  be 
  obtained, 
  and 
  as 
  

   ft 
  = 
  1454(5 
  (0/M)* 
  where 
  6 
  is 
  the 
  absolute 
  temperature, 
  the 
  

   molecular 
  weight 
  M 
  can 
  be 
  calculated, 
  i. 
  e. 
  

  

  M=[3636- 
  5 
  (|-l).^]V 
  

  

  (2) 
  

  

  Experimental 
  Method. 
  

  

  j 
  i 
  JL 
  k 
  

  

  To 
  Pump 
  

  

  The 
  plan 
  of 
  the 
  apparatus 
  used 
  is 
  shown 
  in 
  the 
  figure. 
  

   The 
  arrangement 
  consists 
  essentially 
  of 
  a 
  brass 
  box 
  divided 
  

   symmetrically 
  into 
  two 
  cubes 
  of 
  6*5 
  cm. 
  side 
  by 
  a 
  partition 
  

   having 
  a 
  hole 
  of 
  the 
  order 
  1 
  sq. 
  mm. 
  in 
  thin 
  alumiuium. 
  

  

  