﻿Hypothesis, 
  and 
  the 
  Periodic 
  Law. 
  409 
  

  

  motion 
  likewise 
  checked, 
  and 
  the 
  four 
  repulsions 
  would 
  as 
  to 
  

   their 
  tendency 
  to 
  produce 
  rotation, 
  be 
  more 
  or 
  less 
  balanced, 
  

   with 
  the 
  tendency 
  nil 
  or 
  very 
  small 
  in 
  the 
  case 
  of 
  one 
  molecule, 
  

   while 
  in 
  the 
  case 
  of 
  the 
  other, 
  the 
  tendency 
  would 
  depend 
  

   partly 
  on 
  the 
  circumstances 
  of 
  the 
  encounter, 
  but 
  could 
  not 
  

   exceed 
  a 
  certain 
  maximum 
  value, 
  depending 
  on 
  the 
  ratio 
  of 
  the 
  

   distance 
  between 
  the 
  component 
  atoms 
  to 
  d, 
  the 
  imaginary 
  

   molecular 
  diameter 
  or 
  least 
  distance 
  of 
  approach. 
  The 
  greater 
  

   this 
  ratio 
  the 
  less 
  the 
  tendency 
  for 
  internal 
  rotation. 
  Now 
  

   in 
  a 
  gaseous 
  system 
  as 
  we 
  would 
  have 
  all 
  possible 
  variations 
  in 
  

   the 
  circumstances 
  of 
  the 
  individual 
  encounters, 
  so 
  also 
  would 
  

   we 
  have 
  all 
  possible 
  values 
  of 
  the 
  internal 
  rotations 
  from 
  the 
  

   maximum 
  value 
  thus 
  imposed, 
  down 
  to 
  zero 
  ; 
  but 
  the 
  average 
  

   value 
  of 
  this 
  rotation 
  would 
  be 
  constant, 
  and 
  bear 
  a 
  fixed 
  rela- 
  

   tion 
  to 
  the 
  maximum 
  value, 
  and 
  it 
  would 
  be 
  this 
  fixed 
  average 
  

   value 
  which 
  would 
  determine 
  the 
  ratio 
  of 
  the 
  translatory 
  to 
  the 
  

   rotatory 
  energy, 
  so 
  that 
  a 
  near 
  approach 
  of 
  the 
  ratio 
  of 
  the 
  two 
  

   specific 
  heats 
  to 
  the 
  value 
  1'66 
  would 
  merely 
  indicate 
  that 
  the 
  

   distance 
  between 
  the 
  atoms 
  in 
  the 
  molecule 
  was 
  so 
  small 
  com- 
  

   pared 
  to 
  their 
  least 
  distance 
  of 
  approach, 
  that 
  their 
  mutual 
  

   action 
  on 
  each 
  other 
  was 
  the 
  same 
  as 
  if 
  all 
  of 
  their 
  matter 
  was 
  

   concentrated 
  close 
  to 
  their 
  respective 
  centers 
  of 
  gravity. 
  

  

  Now 
  have 
  we 
  not 
  here 
  the 
  explanation 
  of 
  that 
  hitherto 
  unex- 
  

   plained 
  fact 
  the 
  varying 
  values 
  of 
  this 
  ratio 
  which 
  we 
  find 
  

   in 
  diatomic 
  gases? 
  Thus 
  the 
  molecular 
  gram 
  of 
  O 
  2 
  , 
  N 
  2 
  , 
  H% 
  

   NO 
  and 
  CO 
  has 
  about 
  1*92 
  cals. 
  of 
  internal 
  energy 
  while 
  that 
  

   of 
  CI 
  2 
  and 
  Br 
  2 
  has 
  about 
  3-84 
  cals 
  or 
  twice 
  as 
  much. 
  Ostwald's 
  

   values 
  are 
  

  

  H 
  2 
  and 
  N 
  2 
  = 
  1-82 
  CO 
  =1*86 
  NO 
  = 
  1-95 
  O 
  2 
  = 
  1*96 
  

  

  CI 
  2 
  and 
  Br 
  2 
  = 
  3-84* 
  

  

  In 
  Halogen 
  Group 
  "VII 
  strong 
  chemical 
  affinity 
  for 
  other 
  ele- 
  

   ments 
  would 
  imply 
  corresponding 
  weakness 
  in 
  the 
  force 
  aggre- 
  

   gating 
  the 
  atoms 
  in 
  the 
  molecule, 
  hence 
  a 
  greater 
  distance 
  

   between 
  those 
  atoms 
  compared 
  with 
  their 
  molecular 
  diameter, 
  

   therefore 
  large 
  atomic 
  volume 
  which 
  we 
  find 
  to 
  be 
  the 
  case, 
  

   the 
  volumes 
  of 
  the 
  Group 
  (YII) 
  being 
  comparable 
  in 
  size 
  only 
  

   with 
  those 
  of 
  Group 
  I 
  where 
  the 
  same 
  conditions 
  apply 
  with 
  

   equal 
  force 
  ; 
  and 
  Ostwald 
  has 
  said 
  " 
  The 
  two 
  conceptions 
  of 
  

   chemical 
  affinity, 
  stability 
  on 
  the 
  one 
  hand 
  and 
  activity 
  on 
  the 
  

   other 
  have 
  been 
  confused 
  . 
  . 
  . 
  Thus 
  it 
  is 
  the 
  chemically 
  inac- 
  

   tive 
  bodies 
  that 
  are 
  held 
  together 
  by 
  the 
  most 
  powerful 
  affinity, 
  

   compounds 
  which 
  react 
  with 
  ease 
  and 
  rapidity 
  can 
  only 
  hold 
  

   their 
  components 
  loosely 
  bound 
  if 
  at 
  all." 
  

  

  * 
  Ostwald 
  gives 
  a 
  lower 
  value 
  for 
  Br, 
  but 
  Regnault's 
  specific 
  heat 
  determination 
  

   leads 
  to 
  practically 
  the 
  same 
  value 
  (3.84) 
  as 
  for 
  CI. 
  

  

  Am. 
  Jour. 
  Sci.— 
  Third 
  Series, 
  Vol. 
  XLIX, 
  No. 
  293.— 
  Mat, 
  1895. 
  

  

  21 
  

  

  