﻿338 
  Dr. 
  H. 
  S. 
  Allen 
  on 
  Molecular 
  

  

  when 
  what 
  I 
  hold 
  to 
  be 
  more 
  correct 
  equations 
  of 
  motion 
  

   are 
  used. 
  

  

  Note. 
  — 
  At 
  Sir 
  Oliver 
  Lodge's 
  request 
  I 
  have 
  calculated 
  

   m 
  1 
  and 
  m 
  2 
  for 
  Bucherer's 
  electron 
  which 
  has 
  the 
  same 
  form 
  

   as 
  Lorentz's 
  electron 
  but 
  keeps 
  its 
  volume 
  unchanged. 
  My 
  

   results 
  are 
  

  

  so 
  that 
  

  

  m^m^l 
  + 
  g 
  v*/c*), 
  m 
  2 
  = 
  m 
  (l 
  + 
  § 
  v*/c*\ 
  

  

  Pi- 
  h 
  =2Q- 
  

  

  XXXVII. 
  Molecular 
  Frequency 
  and 
  Molecular 
  JSumber. 
  By 
  

   H. 
  Stanley 
  Allen, 
  M.A., 
  D.Sc, 
  University 
  of 
  London, 
  

   Kings 
  College*. 
  

  

  Part 
  I. 
  

  

  § 
  1. 
  Molecular 
  Number. 
  

  

  THE 
  work 
  of 
  Moseley 
  on 
  the 
  high-frequency 
  spectra 
  of 
  

   the 
  elements 
  has 
  established 
  securely 
  the 
  importance 
  

   of 
  the 
  "atomic 
  number 
  " 
  of 
  an 
  element: 
  that 
  is, 
  the 
  number 
  

   which 
  determines 
  the 
  place 
  in 
  the 
  periodic 
  classification 
  and 
  

   fixes 
  the 
  charge 
  carried 
  by 
  the 
  central 
  part 
  of 
  the 
  atom. 
  It 
  

   is 
  now 
  certain 
  that 
  the 
  atomic 
  number 
  is 
  more 
  fundamental 
  

   than 
  the 
  atomic 
  weight. 
  Recent 
  investigations 
  of 
  the 
  atomic 
  

   weight 
  of 
  lead 
  of 
  radioactive 
  origin 
  have 
  shown 
  that 
  the 
  

   value 
  obtained 
  for 
  this 
  quantity 
  depends 
  upon 
  the 
  source 
  

   from 
  which 
  the 
  material 
  is 
  derived. 
  An 
  interesting 
  account 
  

   of 
  these 
  researches 
  has 
  been 
  given 
  by 
  Soddyt, 
  who 
  points 
  

   out 
  that 
  the 
  atomic 
  weight 
  as 
  ordinarily 
  understood 
  is 
  not 
  

   the 
  unique 
  quantity 
  hitherto 
  supposed. 
  In 
  the 
  Euture 
  in- 
  

   creasing 
  importance 
  will 
  be 
  attached 
  to 
  the 
  atomic 
  number. 
  

   It 
  is 
  the 
  conviction 
  of 
  the 
  present 
  author 
  that 
  this 
  will 
  prove 
  

   true 
  not 
  only 
  in 
  connexion 
  with 
  the 
  properties 
  of 
  the 
  chemical 
  

   elements 
  but 
  also 
  in 
  dealing 
  with 
  compounds. 
  In 
  the 
  latter 
  

   case 
  it 
  is 
  convenient 
  to 
  introduce 
  the 
  term 
  " 
  molecular 
  

   number 
  " 
  to 
  signify 
  the 
  sum 
  of 
  the 
  positive 
  charges 
  carried 
  

   by 
  the 
  atomic 
  nuclei 
  contained 
  in 
  the 
  molecule. 
  Thus 
  when 
  

   a 
  molecule 
  contains 
  a 
  atoms 
  of 
  an 
  element 
  A, 
  b 
  atoms 
  of 
  B, 
  

   c 
  atoms 
  of 
  C, 
  so 
  that 
  its 
  chemical 
  formula 
  is 
  AaBjCc, 
  the 
  

   molecular 
  number 
  T$ 
  = 
  aN 
  a 
  + 
  b'N? 
  > 
  + 
  c'Nc, 
  where 
  N 
  a 
  , 
  Nj, 
  N 
  c 
  are 
  

   the 
  atomic 
  numbers 
  of 
  the 
  component 
  elements. 
  For 
  

  

  * 
  Communicated 
  by 
  the 
  Author. 
  

  

  t 
  Royal 
  Institution 
  Lecture, 
  'Nature/ 
  vol. 
  xcix. 
  p. 
  414 
  (1917). 
  

  

  