﻿Radium 
  and 
  other 
  Elementary 
  Substances. 
  825 
  

  

  the 
  products, 
  minus 
  the 
  atomic 
  weight 
  of 
  the 
  first 
  member 
  

   (Li 
  7), 
  be 
  the 
  atomic 
  weights 
  of 
  the 
  elements 
  of 
  this 
  series. 
  

   It 
  will 
  also 
  be 
  obvious 
  that 
  had 
  these 
  relations 
  been 
  known 
  

   before 
  the 
  discoveries 
  of 
  rubidium 
  and 
  caesium 
  by 
  Bunsen 
  

   and 
  Kirchhoff, 
  the 
  numbers 
  in 
  my 
  table 
  would 
  have 
  expressed 
  

   the 
  atomic 
  weights 
  and 
  other 
  properties 
  of 
  these 
  elements. 
  

   The 
  like 
  remark 
  also 
  applies 
  to 
  the 
  atomic 
  weight 
  of 
  lithium, 
  

   which 
  before 
  Bunsen's 
  accurate 
  determination 
  was 
  accepted 
  

   as 
  6*5. 
  Again, 
  by 
  multiplying 
  in 
  like 
  manner 
  the 
  atomic 
  

   weight 
  of 
  the 
  second 
  member 
  of 
  the 
  alkaline 
  earth 
  and 
  zinc 
  

   series 
  of 
  metals 
  (Mg24) 
  the 
  products, 
  minus 
  the 
  atomic 
  

   weight 
  of 
  the 
  first 
  member 
  (G18), 
  are 
  the 
  atomic 
  w 
  r 
  eights 
  of 
  

   all 
  the 
  elements 
  of 
  this 
  series. 
  

  

  In 
  a 
  note 
  presented 
  to 
  the 
  French 
  Academie 
  des 
  Sciences* 
  

   I 
  have 
  shown 
  that 
  helium 
  is 
  the 
  typical 
  element 
  of 
  the 
  series 
  

   H2n 
  with 
  an 
  atomic 
  weight 
  of 
  2 
  (He 
  = 
  2) 
  ; 
  a 
  value 
  now 
  

   adopted 
  by 
  French 
  chemists 
  in 
  the 
  table 
  of 
  atomic 
  weights 
  

   published 
  in 
  the 
  Annuaire 
  dv 
  Bureau 
  des 
  Longitudes. 
  This 
  

   value 
  is 
  in 
  accordance 
  with 
  the 
  law 
  that 
  the 
  atomic 
  weights 
  

   of 
  the 
  other 
  elementary 
  gases 
  (H, 
  0, 
  N, 
  01) 
  at 
  ordinary 
  

   temperatures 
  are 
  expressed 
  by 
  the 
  same 
  numbers 
  as 
  their 
  

   specific 
  gravities. 
  

  

  I 
  would 
  also 
  direct 
  attention 
  (1) 
  to 
  the 
  common 
  numerical 
  

   difference 
  of 
  4 
  between 
  the 
  halogens 
  and 
  the 
  alkaline 
  metals 
  

   in 
  homologous 
  positions, 
  and 
  (2) 
  the 
  common 
  difference 
  of 
  

   8 
  between 
  the 
  oxygen 
  series 
  and 
  the 
  alkaline 
  earth 
  metals 
  in 
  

   similar 
  positions, 
  (3) 
  the 
  natural 
  arrangement 
  and 
  extension 
  

   of 
  Dumas' 
  triads, 
  in 
  which 
  the 
  sum 
  of 
  the 
  atomic 
  weights 
  of 
  

   the 
  extremes 
  is 
  equal 
  to 
  double 
  the 
  atomic 
  weights 
  of 
  the 
  

   means. 
  

  

  The 
  absolute 
  parallelism 
  of 
  the 
  positive 
  and 
  negative 
  series 
  

   of 
  elements 
  Hn 
  and 
  H2n 
  in 
  their 
  numerical, 
  chemical, 
  and 
  

   physical 
  relations, 
  together 
  with 
  their 
  close 
  resemblance 
  to 
  

   homologous 
  series, 
  will 
  be 
  at 
  once 
  apparent 
  to 
  philosophical 
  

   chemists. 
  The 
  cause 
  of 
  the 
  alternation 
  of 
  light 
  and 
  heavy 
  

   elements 
  in 
  each 
  of 
  these 
  series, 
  while 
  preserving 
  the 
  

   same 
  multiple 
  relations, 
  is 
  a 
  problem 
  for 
  future 
  science 
  to 
  

   solve. 
  

  

  The 
  small 
  differences 
  observable 
  between 
  the 
  experimental 
  

   and 
  a 
  few 
  of 
  the 
  theoretic 
  atomic 
  weights, 
  when 
  distributed 
  

   among 
  the 
  twenty-four 
  members 
  of 
  the 
  four 
  positive 
  and 
  

   negative 
  series, 
  are 
  less 
  than 
  half 
  of 
  one 
  per 
  cent, 
  of 
  the 
  

   actual 
  determinations. 
  

  

  * 
  Comptes 
  Rendus, 
  tome 
  cxxv. 
  p. 
  651 
  (1897). 
  

  

  