﻿946 
  Prof. 
  Rutherford 
  and 
  Mr. 
  Richardson 
  : 
  Analysis 
  of 
  

  

  from 
  actinium 
  B, 
  /a 
  = 
  31, 
  and 
  from 
  mesothorium 
  2, 
  yu,=26, 
  

   belong 
  to 
  the 
  " 
  L 
  " 
  series 
  of 
  Barkla. 
  This 
  type 
  of 
  radiation 
  

   seems 
  very 
  persistent 
  in 
  all 
  except 
  the 
  three 
  products 
  

   radium 
  C, 
  thorium 
  D, 
  and 
  actinium 
  D. 
  It 
  should 
  be 
  pointed 
  

   out, 
  however, 
  that 
  there 
  appears 
  to 
  be 
  no 
  very 
  close 
  con- 
  

   nexion 
  between 
  the 
  penetrating 
  power 
  of 
  the 
  radiation 
  and 
  

   the 
  atomic 
  weight. 
  For 
  example, 
  radium 
  B 
  of 
  atomic 
  

   weight 
  214 
  gives 
  a 
  radiation 
  for 
  which 
  //, 
  = 
  40, 
  whilst 
  thorium 
  

   B 
  of 
  still 
  lower 
  atomic 
  weight 
  2 
  1 
  2 
  gives 
  a 
  more 
  penetrating- 
  

   radiation, 
  yu, 
  = 
  32. 
  This 
  peculiarity 
  holds 
  not 
  only 
  for 
  the 
  

   soft 
  radiations 
  but 
  also 
  for 
  the 
  hard 
  types 
  emitted 
  by 
  the 
  B 
  

   products. 
  If 
  the 
  softer 
  types 
  of 
  radiation 
  do 
  belong 
  to 
  the 
  

   " 
  L 
  " 
  series, 
  it 
  would 
  appear 
  that 
  the 
  general 
  rule 
  connecting 
  

   penetrating 
  power 
  and 
  atomic 
  weight 
  may 
  hold 
  approxi- 
  

   mately 
  over 
  wide 
  ranges 
  but 
  not 
  necessarily 
  for 
  products 
  

   whose 
  atomic 
  weights 
  differ 
  only 
  slightly 
  from 
  one 
  another. 
  

   It 
  is 
  difficult 
  to 
  offer 
  any 
  explanation 
  why 
  the 
  B 
  products 
  

   should 
  give 
  three 
  types 
  and 
  the 
  successive 
  products 
  only 
  one 
  

   type. 
  It 
  should 
  be 
  pointed 
  out, 
  however, 
  that 
  the 
  {3 
  rays 
  from 
  

   the 
  B 
  products 
  are 
  on 
  the 
  average 
  much 
  less 
  penetrating 
  

   than 
  the 
  /3 
  rays 
  from 
  the 
  following 
  products, 
  and 
  have 
  conse- 
  

   quently 
  a 
  much 
  better 
  chance 
  of 
  exciting 
  the 
  softer 
  types 
  

   of 
  7 
  radiation, 
  that 
  is, 
  the 
  radiations 
  of 
  longer 
  wave-length. 
  

   Also 
  it 
  should 
  be 
  noted 
  that 
  the 
  expulsion 
  of 
  a 
  long 
  range 
  

   a 
  particle 
  either 
  accompanies 
  or 
  precedes 
  immediately 
  the 
  

   penetrating 
  7 
  radiation 
  from 
  these 
  products. 
  

  

  During 
  the 
  present 
  year, 
  Russell 
  *, 
  Eajans 
  t, 
  and 
  Soddy 
  J 
  

   have 
  independently 
  discussed 
  the 
  question 
  of 
  the 
  chemical 
  

   properties 
  of 
  the 
  numerous 
  radioactive 
  products, 
  and 
  have 
  

   shown 
  that 
  the 
  sequence 
  of 
  chemical 
  properties 
  in 
  a 
  radio- 
  

   active 
  series 
  follows 
  a 
  simple 
  rule 
  when 
  the 
  types 
  of 
  emitted 
  

   radiation 
  are 
  taken 
  into 
  account. 
  According 
  to 
  some 
  of 
  

   these 
  views, 
  the 
  B 
  products 
  are 
  to 
  be 
  regarded 
  as 
  chemically 
  

   identical 
  and 
  inseparable 
  from 
  one 
  another, 
  although 
  they 
  

   may 
  differ 
  by 
  about 
  two 
  units 
  in 
  their 
  atomic 
  weights. 
  If 
  

   we 
  take 
  the 
  view 
  that 
  the 
  atom 
  consists 
  of 
  a 
  positively 
  

   charged 
  nucleus 
  of 
  small 
  dimensions 
  surrounded 
  by 
  rings 
  of 
  

   electrons 
  which 
  can 
  be 
  set 
  in 
  vibration, 
  it 
  would 
  seem 
  

   probable 
  that 
  an 
  identity 
  of 
  chemical 
  nature 
  would 
  involve 
  

   an 
  identity 
  in 
  the 
  electronic 
  distribution 
  and 
  of 
  the 
  magni- 
  

   tude 
  of 
  the 
  charge 
  on 
  the 
  nucleus. 
  If 
  the 
  7 
  rays 
  set 
  up 
  

   are 
  due 
  to 
  the 
  vibration 
  of 
  the 
  electronic 
  systems, 
  it 
  would 
  

   be 
  anticipated 
  that 
  the 
  types 
  of 
  7 
  rays 
  emitted 
  would 
  be 
  

   identical 
  for 
  such 
  products. 
  While, 
  as 
  we 
  have 
  previously 
  

  

  * 
  Russell, 
  Chem. 
  News, 
  cvii. 
  p. 
  49 
  (1913). 
  

   t 
  Fajans, 
  Phys. 
  Zeit. 
  iv. 
  p. 
  1S6 
  (1913). 
  

   X 
  Soddy, 
  Chem. 
  News, 
  cviii. 
  p. 
  168 
  (1913). 
  

  

  